US20140231852A1

US20140231852A1 - Led chip resistant to electrostatic discharge and led package including the same

Info

Publication number: US20140231852A1
Application number: US14/181,094
Authority: US
Inventors: Duk Il SUH; Kyoung Wan Kim; Yeo Jin Yoon; Sang Won Woo; Shin Hyoung Kim
Original assignee: Seoul Viosys Co Ltd
Current assignee: Seoul Viosys Co Ltd
Priority date: 2013-02-15
Filing date: 2014-02-14
Publication date: 2014-08-21
Also published as: US20150318443A1; WO2014126437A1; US9929315B2

Abstract

A light emitting diode chip and a light emitting diode package including the same. The light emitting diode chip includes a substrate, a light emitting diode section disposed on the substrate, an inverse parallel diode section disposed on the substrate and connected inversely parallel to the light emitting diode section. In the light emitting diode chip, the light emitting diode section is disposed together with the inverse parallel diode section.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from and the benefit of Korean Patent Application
No. 10-2013-0016458, filed on Feb. 15, 2013; Korean Patent Application No. 10-2013-0047383, filed on Apr. 29, 2013; and Korea Patent Application No. 10-2013-0077234, filed on Jul. 2, 2013, all of which are hereby incorporated by reference for all purposes as if fully set forth herein.

BACKGROUND

1. Field
Exemplary embodiments of the present invention relate to a light emitting device, and more particularly, to a light emitting diode chip that is resistant to electrostatic discharge, and a light emitting diode package including the same.
2. Discussion of the Background
Generally, GaN-based compound semiconductors are formed by epitaxial growth on a sapphire substrate, which has a similar crystal structure and lattice parameter thereto, in order to reduce lattice defects. However, epitaxial layers grown on the sapphire substrate may have many types of crystal defects, such as V-fits, threading dislocations, and the like. When high voltage static electricity is applied to a light emitting diode from outside, current is concentrated in crystal defects in the epitaxial layers, thereby causing diode breakdown.
Recently, the number of applications of high brightness/high output light emitting diodes (LEDs) has increased, not only to backlight units of LED TVs, but also to luminaries, automobiles, electric signboards, facilities, and the like. Accordingly, there is an increasing demand for the protection of light emitting devices against static electricity.
For LEDs, it is desirable to secure a semi-permanent lifespan using an ESD protection device having excellent electric reliability. It is very important to secure reliability of LEDs with respect to electrostatic discharge (ESD), electrical fast transient (EFT), which refers to sparks occurring in a switch, and electrical surges resulting from lightning and the like.
Generally, when packaging a light emitting diode, a separate Zener diode is mounted together with the light emitting diode to prevent electrostatic discharge. However, the Zener diode is expensive and several processes are used for mounting, thereby increasing manufacturing costs, as well as the number of processes for packaging the light emitting diode.
Moreover, because the Zener diode is disposed near the light emitting diode in an LED package, luminous efficacy of the package is reduced as a result of absorption of light by the Zener diode, thereby deteriorating light yield of the LED package.
On the other hand, various attempts have been made to provide a light emitting diode chip resistant to ESD using a stacked structure of epitaxial layers in the light emitting diode chip. For example, a super lattice layer may be disposed between an n-type semiconductor layer and an active layer. With this structure, the super lattice layer can reduce lattice defects in the active layer, thereby providing a light emitting diode chip resistant to ESD. However, this technique still does not provide good yield.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and, therefore, it may contain information that does not constitute prior art.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention provide a light emitting diode chip having high resistance to electrostatic discharge at a chip level, and a light emitting diode package including the same.
Exemplary embodiments of the present invention also provide a light emitting diode chip having high resistance to electrostatic discharge, and which is free from reduction in light output or an increase in forward voltage, and a light emitting diode package including the same.
Exemplary embodiments of the present invention also provide a light emitting diode chip having high resistance to electrostatic discharge, and which exhibits improved luminous efficacy at the chip level and/or package level, and a light emitting diode package including the same.
Additional features of the invention will be set forth in the description which follows, and in part will become apparent from the description, or may be learned from practice of the invention.
An exemplary embodiment of the present invention discloses a light emitting diode chip including: a substrate; a light emitting diode section disposed on the substrate; and an inverse parallel diode section disposed on the substrate and connected inversely parallel to the light emitting diode section. In the light emitting diode chip, the light emitting diode section is disposed together with the inverse parallel diode section, whereby the light emitting diode chip exhibits high resistance to electrostatic discharge.
The substrate may be a growth substrate capable of growing a nitride semiconductor layer thereon, and may be, for example, a patterned sapphire substrate (PSS).
Each of the light emitting diode section and the inverse parallel diode section may include a first conductivity type nitride semiconductor layer; a second conductivity type nitride semiconductor layer; and an active layer disposed between the first conductivity type nitride semiconductor layer and the second conductivity type nitride semiconductor layer. The light emitting diode section and the inverse parallel diode section may have the same stack structure, and may be formed using epitaxial layers which are grown together through the same growth process. On the other hand, the second conductivity type nitride semiconductor layer of the light emitting diode section and the second conductivity type nitride semiconductor layer of the inverse parallel diode section may have different thicknesses. For example, the second conductivity type nitride semiconductor layer of the inverse parallel diode section may have a smaller thickness than that of the light emitting diode section. With this structure, the inverse parallel diode section may have a lower height than the light emitting diode section.
The light emitting diode chip may further include a first electrode pad and a second electrode pad, wherein the first electrode pad may be disposed on the inverse parallel diode section, and the second electrode pad may be disposed on the light emitting diode section.
Because the first electrode pad is disposed on the inverse parallel diode section, it is possible to secure a larger activation area than in the case where the first electrode pad is formed on the light emitting diode section.
The light emitting diode chip may further include a first extension extending from the first electrode pad; and a second extension extending from the second electrode pad. The first extension may be electrically connected to the first conductivity type nitride semiconductor layer of the light emitting diode section, and the second extension may be electrically connected to the first conductivity type nitride semiconductor layer of the inverse parallel diode section.
The first electrode pad and the second extension may be horizontally separated from each other. A portion of the first electrode pad may be disposed on the second extension electrically connected to the first conductivity type nitride semiconductor layer of the inverse parallel diode section. In addition, the light emitting diode chip may further include an isolation layer insolating the first electrode pad from the second extension.
In addition, the first extension may be connected to the first conductivity type nitride semiconductor layer at a plurality of points on the light emitting diode section.
The first extension may pass through an upper portion of the second conductivity type nitride semiconductor layer of the light emitting diode section, and the first extension may be electrically insulated from the second conductivity type nitride semiconductor layer by the insulation layer. Alternatively, the first extension may be linearly connected to the first conductivity type nitride semiconductor layer of the light emitting diode section.
The light emitting diode chip may further include a second transparent electrode layer disposed between the first electrode pad and the second conductivity type nitride semiconductor layer of the inverse parallel diode section. The second transparent electrode layer helps the first electrode pad to electrically connect to the second conductivity type nitride semiconductor layer. When the first electrode pad is electrically connected to the second conductivity type nitride semiconductor layer, the second transparent electrode layer may be omitted.
The light emitting diode chip may further include a first transparent electrode layer connected to an upper surface of the second conductivity type nitride semiconductor layer of the light emitting diode section. The second electrode pad may be disposed on the first transparent electrode layer. In addition, the light emitting diode chip may further include a current blocking layer disposed under a region for the first transparent electrode layer below the second electrode pad.
The light emitting diode chip may further include a current blocking layer disposed under a region for the first transparent electrode layer below the second extension.
The light emitting diode chip may further include a reflector covering at least a portion of the inverse parallel diode section. With the reflector disposed to cover the inverse parallel diode section, the light emitting diode chip has improved luminous efficacy.
The reflector may be a distributed Bragg reflector (DBR).
At least a portion of the reflector may extend to the light emitting diode section to insulate the second extension from a side surface of the light emitting diode section. In other words, the reflector may be disposed between the second extension and the side surface of the light emitting diode section. Furthermore, the reflector may extend to an upper side of the second conductivity type semiconductor layer of the light emitting diode section.
Furthermore, at least a portion of the reflector may extend to the light emitting diode section to insulate the first extension from the light emitting diode section. The first extension may be insulated from the second conductivity type semiconductor layer of the light emitting diode section by the reflector.
The reflector may cover the inverse parallel diode section so as to enclose the first electrode pad and may have an opening, through which the first conductivity type nitride semiconductor layer connected to the second extension is exposed. The reflector may cover substantially an overall region of the inverse parallel diode section except for the first electrode pad region and the opening.
In addition, the current blocking layer may be a distributed Bragg reflector (DBR).
At least one of the first and second extensions may include a reflective metal layer formed on an upper side thereof.
An exemplary embodiment of the present invention also discloses a light emitting diode chip including a substrate; a light emitting diode section disposed on the substrate; an inverse parallel diode section disposed on the substrate; a first electrode pad disposed on the inverse parallel diode section; a second electrode pad disposed on the light emitting diode section; a first extension extending from the first electrode pad and connected to the light emitting diode section; and a second extension extending from the second electrode pad and connected to the inverse parallel diode section. The inverse parallel diode section may be connected inversely parallel to the light emitting diode section. When the inverse parallel diode section is formed on a region on which the first electrode pad is formed, the light emitting diode chip exhibits high resistance to electrostatic discharge, while preventing a reduction in light emitting area.
An exemplary embodiment of the present invention also discloses a light emitting diode package including a chip mounting section having a chip mounting face and a light emitting diode chip mounted on the chip mounting face. The light emitting diode chip may include a substrate; a light emitting diode section disposed on the substrate; and an inverse parallel diode section disposed on the substrate and connected inversely parallel to the light emitting diode section. The light emitting diode chip may further include a reflector covering at least a portion of the inverse parallel diode section.
By adopting the light emitting diode chip, there is no need to mount a separate Zener diode inside the package, thereby preventing increase in optical loss or process cost due to mounting of the Zener diode.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention, and together with the description serve to explain the principles of the invention.

FIG. 1 is a schematic plan view of a light emitting diode chip according to an exemplary embodiment of the present invention.

FIG. 2 is a schematic sectional view taken along line A-A of FIG. 1.

FIG. 3 is a schematic sectional view taken along line B-B of FIG. 1.

FIG. 4 is a schematic sectional view taken along line C-C of FIG. 1.

FIG. 5 is a schematic circuit diagram of a light emitting diode chip according to an exemplary embodiment of the present invention.

FIGS. 6( a) and 6(b) are schematic plan views of light emitting diode chips according to an exemplary embodiment of the present invention.

FIG. 7 is a graph depicting I-V characteristics of a typical light emitting diode chip and light emitting diode chips according to an exemplary embodiment of the present invention.

FIG. 8 is a sectional view of a light emitting diode chip according to an exemplary embodiment of the present invention.

FIG. 9 is a partial plan view of a light emitting diode chip according to an exemplary embodiment of the present invention.

FIG. 10 is a schematic sectional view taken along line D-D of FIG. 9.

FIG. 11 is a partial plan view of a light emitting diode chip according to an exemplary embodiment of the present invention.

FIG. 12 is a schematic sectional view taken along line E-E of FIG. 10.

FIG. 13 is a schematic sectional view taken along line F-F of FIG. 10.

FIG. 14 is a schematic sectional view of a light emitting diode package according to an exemplary embodiment of the present invention.

FIG. 15 is a schematic sectional view of a light emitting diode package according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The invention is described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure is thorough, and will fully convey the scope of the invention to those skilled in the art. Further, it should be noted that the drawings are not to precise scale, and some of the dimensions, such as width, length, thickness, and the like, are exaggerated for clarity of description in the drawings. Like components are denoted by like reference numerals throughout the specification.
It will be understood that when an element or layer is referred to as being “on” or “connected to” another element or layer, it can be directly on or directly connected to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on” or “directly connected to” another element or layer, there are no intervening elements or layers present. It will be understood that for the purposes of this disclosure, “at least one of X, Y, and Z” can be construed as X only, Y only, Z only, or any combination of two or more items X, Y, and Z (e.g., XYZ, XYY, YZ, ZZ).
Referring to FIGS. 1 to 4, the light emitting diode chip includes a substrate 21, a light emitting diode section (Ld), and an inverse parallel diode section (Rd). Further, the light emitting diode chip may include a first transparent electrode layer 31 a, a second transparent electrode layer 31 b, a current blocking layer 33 a, an insulation layer 33 b, a first electrode pad 35, a second electrode pad 37, a first extension 35 a, a second extension 37 a, and an end portion 37 b of the first extension 35 a.
The substrate 21 allows growth of semiconductor epitaxial layers thereon, and may be, for example, a patterned sapphire substrate. As shown in FIGS. 2 to 4, the patterned sapphire substrate has a pattern of protrusions formed on a surface thereof to improve light extraction efficiency by scattering light at the protrusions.
The light emitting diode section (Ld) may include a first conductivity type nitride semiconductor layer 25 a, an active layer 27 a, and a second conductivity type nitride semiconductor layer 29 a, and the inverse parallel diode section (Rd) may include a first conductivity type nitride semiconductor layer 25 b, an active layer 27 b, and a second conductivity type nitride semiconductor layer 29 b. The light emitting diode section (Ld) and the inverse parallel diode section (Rd) are nitride-based stacked regions electrically separated from each other, and may be formed of nitride semiconductor layers. With this structure, the light emitting diode section (Ld) may be disposed to be coplanar with the inverse parallel diode section (Rd) on the same substrate.
The first conductivity type nitride semiconductor layers 25 a, 25 b may include, for example, n-type GaN, and the second conductivity type nitride semiconductor layers 29 a, 29 b may include, for example, p-type GaN, or vice versa. Each of the active layers 27 a, 27 b may be disposed between the first conductivity type nitride semiconductor layer 25 a or 25 b and the second conductivity type nitride semiconductor layer 29 a or 29 b, and may have a single quantum well structure or a multi-quantum well structure.
The light emitting diode section (Ld) and the inverse parallel diode section (Rd) may be formed by patterning nitride semiconductor layers grown by the same growth process, for example, MOCVD, MBE, and the like, to be separated from each other. Accordingly, the first conductivity type nitride semiconductor layer 25 a, the active layer 27 a and the second conductivity type nitride semiconductor layer 29 a may be formed by the same process as that of the first conductivity type nitride semiconductor layer 25 b, the active layer 27 b and the second conductivity type nitride semiconductor layer 29 b. Thus, the first conductivity type nitride semiconductor layer 25 a, the active layer 27 a and the second conductivity type nitride semiconductor layer 29 a may have the same composition and the same impurity density as those of the first conductivity type nitride semiconductor layer 25 b, the active layer 27 b and the second conductivity type nitride semiconductor layer 29 b.
The second conductivity type nitride semiconductor layer 29 b may have a smaller thickness than the second conductivity type nitride semiconductor layer 29 a. For example, the second conductivity type nitride semiconductor layer 29 b may be a thin layer formed by dry etching. As a result, the inverse parallel diode section (Rd) may have a lower height than the light emitting diode section (Ld), thereby reducing absorption of light by the first electrode pad 35.
As shown in FIG. 1, the light emitting diode section (Ld) has a larger area than the inverse parallel diode section (Rd). The inverse parallel diode section (Rd) is formed in a narrow area in which an n-electrode pad is formed, in a typical lateral-type light emitting diode. Thus, there is no substantial reduction in light emitting area resulting from the formation of the inverse parallel diode section (Rd), so that the inverse parallel diode section (Rd) may be disposed in a single chip without reduction in light output or an increase in forward voltage.
The first transparent electrode layer 31 a is disposed on the light emitting diode section (Ld). The first transparent electrode layer 31 a covers an upper surface of the light emitting diode section (Ld). The first transparent electrode layer 31 a electrically contacts the second conductivity type nitride semiconductor layer 29 a, and allows electric current to spread over a wide area of the light emitting diode section (Ld). The second transparent electrode layer 31 b is disposed on the inverse parallel diode section (Rd). The second transparent electrode layer 31 b electrically contacts the second conductivity type nitride semiconductor layer 29 b. Although the second transparent electrode layer 31 b can be omitted, use of the second transparent electrode layer 31 b provides better electrostatic discharge characteristics than the case where the second transparent electrode layer 31 b is omitted. The first transparent electrode layer 31 a and the second transparent electrode layer 31 b may be formed by the same process using, for example, transparent conductive oxides, such as ITO, FTO, ZnO, and the like, or transparent metals such as Ni/Au, without being limited thereto. Furthermore, the second transparent electrode layer 31 b may be formed of a different material than that of the first transparent electrode layer 31 a, and the second transparent electrode layer 31 b may be formed of an opaque material instead of a transparent material. Further, instead of the second transparent electrode layer 31 b, an opaque electrode layer may be formed to make ohmic contact with the second conductivity type nitride semiconductor layer 29 b.
The first electrode pad 35 is disposed on the inverse parallel diode section (Rd), and is electrically connected to the second conductivity type nitride semiconductor layer 29 b. On the other hand, the second electrode pad 37 is disposed on the light emitting diode section (Ld) and is electrically connected to the second conductivity type nitride semiconductor layer 29 a.
The first electrode pad 35 and the second electrode pad 37 are formed to have relatively large areas to allow connection via bonding wires for supplying electric current to the light emitting diode chip. For example, the first electrode pad 35 and the second electrode pad 37 have a larger width than the first extension 35 a or the second extension 37 a, respectively.
The first extension 35 a extends from the first electrode pad 35 and is electrically connected to the first conductivity type nitride semiconductor layer 25 a of the light emitting diode section (Ld). As shown in FIG. 1, the first extension 35 a may be connected to the first conductivity type nitride semiconductor layer 25 a at a plurality of points (6 points are shown in FIG. 1). The first extension 35 a may also pass through an upper portion of the light emitting diode section (Ld), that is, an upper portion of the second conductivity type nitride semiconductor layer 29 a, and may be insulated from the second conductivity type nitride semiconductor layer 29 a by the insulation layer 33 b. Alternatively, the first extension 35 a may be linearly connected to an upper surface of the first conductivity type nitride semiconductor layer 29 a. For example, the first conductivity type nitride semiconductor layer 25 a is consecutively exposed on a side surface of the light emitting diode section (Ld) by mesa etching, and the first extension 35 a may be formed on an exposed region of the first conductivity type nitride semiconductor layer 29 a. The first extension 35 a is also insulated from the first conductivity type nitride semiconductor layer 25 b of the inverse parallel diode section (Rd) by the insulation layer 33 b.
The insulation layer 33 b is disposed between the first extension 35 a and the second conductivity type nitride semiconductor layer 29 a to electrically insulate the first extension 35 a from the second conductivity type nitride semiconductor layer 29 a. Further, the insulation layer 33 b may be disposed near the transparent electrode layers 31 a, 31 b to cover side surfaces of the light emitting diode section (Ld) and the inverse parallel diode section (Rd. As such, the first extension 35 a and the second extension 37 a may be insulated from the side surface of the light emitting diode section (Ld) and the side surface of the inverse parallel diode section (Rd).
The second extension 37 a extends from the second electrode pad 37. The second extension 37 a allows electric current to spread over a wide area of the light emitting diode section (Ld). The second extension 37 a may extend in parallel to the first extension 35 a to face each other. However, the present invention is not limited thereto, and the second extension 37 a may extend in various ways. In addition, the second extension 37 a also extends to the inverse parallel diode section (Rd) such that the end portion 37 b of the second extension is electrically connected to the first conductivity type nitride semiconductor layer 25 b.
As shown in FIG. 4, the end portion 37 b of the second extension is electrically connected to the first conductivity type nitride semiconductor layer 25 b of the inverse parallel diode section (Rd). The end portion 37 b may be disposed on a region of the first conductivity type nitride semiconductor layer 25 b exposed by mesa etching. Alternatively, the inverse parallel diode section (Rd) may be formed to have a generally slanted side surface, and the end portion 37 b may be connected to a region of the first conductivity type nitride semiconductor layer 25 b exposed to the slanted surface of the inverse parallel diode section (Rd). In this case, mesa etching may be omitted, thereby simplifying the manufacturing process.
On the other hand, as shown in FIG. 2, the current blocking layer 33 a may be disposed below the second electrode pad 37. Further, the current blocking layer 33 a is disposed between the first transparent electrode layer 31 a and the second conductivity type nitride semiconductor layer 29 a. The current blocking layer 33 a may be formed of an insulating material, such as silicon oxide, silicon nitride, and the like. The current blocking layer 33 a assists current spreading by preventing direct flow of electric current from the second electrode pad 37 to the second conductivity type nitride semiconductor layer 29 a. The current blocking layer 33 a may extend below the second extension 37 a. Further, the current blocking layer 33 a may extend to the inverse parallel diode section (Rd) side to insulate the second extension 37 a from the first conductivity type nitride semiconductor layer 25 a exposed to the side surface of the light emitting diode section (Ld). Alternatively, the insulation layer separated from the current blocking layer 33 a may insulate the second extension 37 a from the first conductivity type nitride semiconductor layer 25 a exposed to the side surface of the light emitting diode section (Ld).
According to this exemplary embodiment, the inverse parallel diode section (Rd) is formed in an area in which the first electrode pad 35 is formed, thereby improving electrostatic discharge characteristics of the light emitting diode chip while suppressing reduction in light emitting area. Further, as shown in FIG. 5, the first extension 35 a and the second extension 35 b may be used to form an inverse parallel connection circuit in a single light emitting diode chip, in which the light emitting diode section (Ld) and the inverse parallel diode section (Rd) are connected to each other in inverse parallel.
FIGS. 6( a) and 6(b) are schematic plan views of light emitting diode chips according to exemplary embodiments of the present invention. For simple illustration, the same components are denoted by the same reference numerals as those of FIG. 1.
Referring to FIG. 6( a), the light emitting diode chip is generally similar to the light emitting diode chip shown in FIG. 1, except for the relative location between the first electrode pad 35 and the second electrode pad 37, and design of the first extension 35 a and the second extension 37 a. That is, in the light emitting diode chip of FIG. 1, the first electrode pad 35 and the second electrode pad 37 are disposed at a first edge of the light emitting diode chip (at a side to which the second extension 37 a is disposed adjacent), and the first extension 35 a extends from the first electrode pad 35 to a second edge opposite the first edge. On the contrary, in the present exemplary embodiment, a first electrode pad 35 and a second electrode pad 37 are disposed in a diagonal direction, and a second extension 37 a extends farther inside the light emitting diode section (Ld) than a first extension. Here, the second extension 37 has a T-shaped end portion 37 b.
Referring to FIG. 6( b), the light emitting diode chip is similar to the light emitting diode chip of FIG. 6( a) except that a first extension 35 a is linearly connected to a first conductive-type semiconductor layer 25 a. Specifically, in this embodiment, the first extension 35 a is disposed in a linear area, in which a second conductivity type semiconductor layer 29 a and an active layer 27 a are removed by mesa etching, and is consecutively connected to the first conductive-type semiconductor layer 25 a.
The relative location between the first electrode pad 35 and the second electrode pad 37, and locations, shapes and structures of the first extension 35 a and the second extension 37 a may be arranged in various ways.
Light emitting diode chips P1, P2 according to FIG. 1 and FIG. 6( a) were manufactured and evaluated as to electrical and optical characteristics, together with a typical light emitting diode chip (Ref). FIG. 7 shows I-V characteristics of these light emitting diode chips.
Referring to FIG. 7, when inverse electric current is applied to the typical light emitting diode chip (Ref), the electric current does not substantially flow therethrough. Although not shown in the graph, when inverse voltage is increased by 10V or more, breakdown of the light emitting diode chip occurs.
In the light emitting diode chips P1, P6 of FIG. 1 and FIG. 6( a), it can be seen that the inverse parallel diode section (Rd) was turned on and current flows therethrough, as inverse voltage increases.
On the other hand, results of forward voltage (at 20 mA), light output (at 20 mA) and electrostatic discharge (ESD) yield at an inverse voltage of 3 kV of the light emitting diode chips Ref, P1, P2 are summarized in Table 1. For a light emitting diode chip having a typical epitaxial layer structure and an ESD-enhanced light emitting diode chip including a super lattice layer between an active layer and a first conductivity type nitride semiconductor layer for enhancement of ESD, the typical light emitting diode chip (Ref), the light emitting diode chip P1 of the first exemplary embodiment and the light emitting diode chip (P2) of the second exemplary embodiment were manufactured and evaluated as to the above characteristics. Results are shown in Table 1.

TABLE 1

		Forward	Light
Epitaxy	Chip	voltage V	output W	ESD yield
structure	structure	(@20 mA)	(@20 mA)	(@3 kV)

Typical	Ref	2.93	77.3	4%
epitaxy	P1	2.94	76.8	99%
	P2	2.92	75.9	100%
ESD-enhanced	Ref	2.90	80.4	83%
epitaxy	P1	2.93	79.2	99%
	P2	2.90	78.9	99%

Referring to Table 1, as compared with the typical light emitting diode chip, the light emitting diode chips P1, P2 did not exhibit substantial variation in forward voltage, and did not suffer from significant reduction of light output. On the contrary, in terms of ESD yield, the light emitting diode chips P1, P2 exhibited more significantly improved results than the light emitting diode chip of the prior art (Ref). Both the typical epitaxy structure and the ESD-enhanced epitaxy structure provided significantly improved ESD yield. Particularly, the typical epitaxy structure vulnerable to ESD exhibited a high ESD yield of 99% or more.
FIG. 8 is a sectional view of a light emitting diode chip according to a an exemplary embodiment of the present invention. For reference, FIG. 8 corresponds to the sectional view (FIG. 4) taken along line C-C of FIG. 1.
Referring to FIG. 8, the light emitting diode chip is generally similar to the light emitting diode chip described with reference to FIGS. 1 to 4, except that a portion of a first electrode pad 35 is disposed above an end portion 37 b of a first extension. Specifically, at least a portion of the end portion 37 b of the first extension connected to a first conductivity type nitride semiconductor layer 25 b in an inverse parallel diode section (Rd) is disposed below the first electrode pad 35. The end portion 37 b of the first extension is insulated from the first electrode pad 35 by an insulation layer 39.
According to this exemplary embodiment, since it is not necessary to separate the first electrode pad 35 from the end portion 37 b in the horizontal direction, it is possible to provide a light emitting diode chip in which the inverse parallel diode section (Rd) has a relatively small size and the first electrode pad 35 has the same area as that of the light emitting diode chips according to the previously described exemplary embodiments. In addition, as can be seen from comparison of the light emitting diode chip according to the exemplary embodiment as shown in FIG. 8 with the light emitting diode chip according to the exemplary embodiment as shown in FIG. 4, the size of the light emitting diode section (Ld) may be increased while decreasing the size of the inverse parallel diode section (Rd). As a result, it is possible to minimize reduction in light emitting area of the light emitting diode section (Ld) while forming the inverse parallel diode section (Rd) in a single light emitting diode chip.
FIG. 9 is a schematic partial plan view of a light emitting diode chip according to an exemplary embodiment of the invention, and FIG. 10 is a sectional view taken along line D-D of FIG. 9. In the plan view of FIG. 9, the inverse parallel diode section (Rd) and a portion of the light emitting diode section (Ld) around the inverse parallel diode section (Rd) of FIG. 1 are enlarged.
Referring to FIGS. 9 and 10, the light emitting diode chip is generally similar to the light emitting diode chip described with reference to FIGS. 1 to 4 except that the light emitting diode chip includes reflectors 133 a, 133 b.
The reflectors 133 a, 133 b may be distributed Bragg reflectors formed of an insulation layer. The DBR structure may be formed by alternately stacking dielectric layers having different indexes of refraction. For example, the DBR structure may be formed by repeatedly stacking TiO₂/SiO₂, Nb₂O₅/SiO₂or HfO₂/SiO₂. In addition, the DBR structure can maximize reflection through a thin film design adapted for central wavelengths in consideration of spectrum distribution of light to be reflected, thereby preventing optical loss resulting from absorption of light upon use of a single film of SiO₂and the like.
The reflector 133 a is disposed between the second extension 37 a and the light emitting diode section (Ld), and insulates the second extension 37 a from a side surface of the light emitting diode section (Ld). In addition, the reflector 133 a may act as the current blocking layer 33 a described with reference to FIGS. 1 to 4. For example, similar to the current blocking layer 33 a, the reflector 133 a may be disposed between the first transparent electrode layer 31 a and the second conductivity type nitride semiconductor layer 29 a under the second electrode pad 37 and the second extension 37 a. Furthermore, the reflector 133 a may cover a portion of the inverse parallel diode section (Rd). For example, as shown in FIG. 9, the reflector 133 a may cover a portion of the first conductivity type nitride semiconductor layer 25 b of the inverse parallel diode section (Rd).
In other words, the reflector 133 a covers a portion of the inverse parallel diode section (Rd), and may extend to the light emitting diode section (Ld) to insulate the second extension 37 a from the side surface of the light emitting diode section (Ld).
On the other hand, the reflector 133 b covers a portion of the inverse parallel diode section (Rd) and extends to the light emitting diode section (Ld) to insulate the first extension 35 a from the second conductivity type nitride semiconductor layer 29 a of the light emitting diode section (Ld). Namely, in the structure wherein the first extension 35 a passes through an upper portion of the light emitting diode section (Ld), the reflector 133 b is disposed between the first extension 35 a and the second conductivity type nitride semiconductor layer 29 a to prevent short circuits between the first extension 35 a and the second conductivity type nitride semiconductor layer 29 a. In addition, the first extension 35 a is electrically insulated from the first transparent electrode layer 31 a.
Further, as shown in FIG. 9, the reflector 133 b insulates the first extension 35 a from the side surface of the inverse parallel diode section (Rd) and the side surface of the light emitting diode section (Ld) by covering the side surfaces of the inverse parallel diode section (Rd) and the light emitting diode section (Ld). The reflector 133 a may act as the insulation layer 33 b described with reference to FIGS. 1 to 4.
The reflectors 133 a, 133 b prevent optical loss resulting from absorption of light by the first extension 35 a and the second extension 37 a when light is emitted from the light emitting diode section (Ld). Specifically, some of the light emitted from the light emitting diode section (Ld) is directed towards the first extension 35 a and the second extension 37 a, and is reflected by the reflectors 133 a, 133 b to return into the light emitting diode section (Ld). Thereafter, the reflected light can be emitted outside through other portions of the light emitting diode section (Ld).
In this exemplary embodiment, at least one of the first extension 35 a and the second extension 37 a may further include a reflective metal layer 137 formed on upper side(s) thereof, as shown in FIG. 10. The reflective metal layer 137 reduces optical loss by reflecting light entering upper side(s) of the first extension 35 a and/or the second extension 37 a. For example, when light emitted from the light emitting diode section (Ld) is incident on the first extension 35 a and/or the second extension 37 a disposed on the inverse parallel diode section (Rd), the reflective metal layer 137 reflects the light. The reflective metal layer 137 may be formed of, for example, Ni, Al, Ag, Rh, Pt, or combinations thereof.
FIG. 11 is a partial plan view of a light emitting diode chip according to an exemplary embodiment of the present invention, and FIGS. 12 and 13 are sectional views taken along line E-E and line F-F of FIG. 11, respectively.
Referring to FIGS. 11 to 13, the light emitting diode chip is generally similar to the light emitting diode chip described with reference to FIGS. 9 and 10, except that the light emitting diode chip further includes a reflector 133 r. The reflector 133 r may be formed of the same material as that of the reflectors 133 a, 133 b and by the same process.
The reflector 133 r covers an inverse parallel diode section (Rd) so as to enclose a first electrode pad 35. The reflector 133 r has an opening 133 h, through which a first conductivity type nitride semiconductor layer 25 b connected to an end portion 37 b of a second extension 37 a is exposed.
As shown in FIG. 13, the reflector 133 r may cover substantially an entire area of a second conductivity type nitride semiconductor layer 29 b around the first electrode pad 35. In addition, the reflector 133 r may cover a side surface of the inverse parallel diode section (Rd).
The reflector 133 r may reflect light emitted from a light emitting diode section (Ld) and travelling towards the inverse parallel diode section (Rd), thereby preventing the light from re-entering the inverse parallel diode section (Rd). Furthermore, as described below, the reflector 133 r may reflect light entering the inverse parallel diode section (Rd) from a molding section or phosphors of a light emitting diode package, thereby improving luminous efficacy.
FIG. 14 is a sectional view of a light emitting diode package according to yet another embodiment of the present invention.
Referring to FIG. 14, the light emitting diode package includes a chip mounting member 110 having a chip mounting face, a light emitting diode chip 100, at least two leads 111, 113, and bonding wires 115.
For the chip mounting member 110, any member may be used which can mount the light emitting diode chip 100 thereon. For example, the chip mounting member 110 may be a lead frame type package body, a printed circuit board, and the like. The light emitting diode chip 100 may be the light emitting diode chip described with reference to FIGS. 1 to 4, the light emitting diode chip described with reference to FIG. 6, the light emitting diode chip described with reference to FIGS. 9 and 10, or the light emitting diode chip described with reference to FIGS. 11 to 13, and detailed descriptions thereof will be omitted.
The first electrode pad 35 and the second electrode pad 37 of the light emitting diode chip are electrically connected to the leads 111, 113 via the bonding wires 115.
FIG. 15 is a sectional view of a light emitting diode package according to an exemplary embodiment of the present invention.
Referring to FIG. 15, the light emitting diode package includes a chip mounting member 110 having a chip mounting face and a light emitting diode chip 100. In addition, the light emitting diode package may include at least two leads 111, 113, bonding wires 115, and a molding section 117. The light emitting diode package may further include a wavelength converter (not shown).
The light emitting diode package according to FIG. 15 is generally similar to the light emitting diode package according to the exemplary embodiment shown in FIG. 14, except that the light emitting diode package according to the present embodiment includes the molding section 117 and the wavelength converter. Hereinafter, the light emitting diode package according to the present embodiment will be described in more detailed with regard to different components, and repeated descriptions of the components will be omitted.
The molding section 117 covers the light emitting diode chip 100. The molding section 117 may contain phosphors and, thus, may act as a wavelength converter. Alternatively, a separate wavelength converter independent of the molding section 117 may be disposed on the molding section 117 or on the light emitting diode chip 100. The wavelength converter converts wavelengths of light emitted from the light emitting diode chip 100.
Light emitted from the light emitting diode chip 100 enters the molding section 117, and some of the light entering the molding section 117 is directed again towards the light emitting diode chip 100. Particularly, when a wavelength converter including phosphors is used, some of light subjected to wavelength conversion by the wavelength converter may be directed towards the light emitting diode chip 100. In this case, in the light emitting diode chips described with reference to FIGS. 11 to 13, light is reflected by the reflector 133 r covering substantially the overall area of the inverse parallel diode section (Rd), thereby improving the luminous efficacy of the package.
In order to evaluate ESD characteristics at the package level of light emitting diode chips according to examples of the present invention, light emitting diode chips having passed ESD testing at 3 kV at the chip level were evaluated as to ESD characteristics at the package level. Each of the light emitting diode chips used in this evaluation had an ESD-enhanced epitaxy structure, which includes a super lattice layer between the active layer and the first conductivity type nitride semiconductor layer for enhancement of ESD characteristics, and had the same structure as that of the light emitting diode chip according to the exemplary embodiment (P1) shown in FIG. 1. Here, the light emitting diode chip of Example 1 did not include the second transparent electrode layer 31 b, and the light emitting diode chip of Example 2 employed indium tin oxide (ITO) as the second transparent electrode layer 31 b. For twenty test packages of each of Examples 1 and 2, ESD yield was measured while increasing ESD testing voltage from 1 kV to 4 kV. Results are shown in Table 2.

	TABLE 2

	ESD Yield

	@1 kV	@2 kV	@3 kV	@4 KV

Example 1	100%	100%	85%	0%
Example 2	100%	100%	100%	100%

Referring to Table 2, it can be seen that, when the second transparent electrode layer 31 b was not included, device failure occurred due to electrostatic discharge at 3 kV or higher. On the contrary, when the second transparent electrode layer 31 b was used, there was no device failure even at 4 kV. As a consequence, it can be seen that the second transparent electrode layer 31 b enhances ESD characteristics.
According to the present invention, because the light emitting diode chip 100 includes the inverse parallel diode section (Rd), there is no need for a separate protective device for prevention of electrostatic discharge, for example, a Zener diode, in a light emitting diode package. Accordingly, the present invention may simplify a manufacturing process through elimination of a process for mounting the Zener diode, and may improve luminous efficacy of the package by preventing absorption of light by the Zener diode. Furthermore, the light emitting diode chip according to the present invention includes the reflector 133 r to reduce re-absorption of light into the light emitting diode chip 100, thereby improving luminous efficacy.
In the light emitting diode chip according to the present invention, the light emitting diode section and the inverse parallel diode section are formed on the same substrate, whereby the light emitting diode chip exhibits high resistance to electrostatic discharge and does not need a separate ESD protection device, such as a Zener diode.
In addition, the inverse parallel diode section is formed on the region of the first electrode pad, thereby preventing reduction in the light emitting area. As a result, the light emitting diode chip may adopt an inverse-parallel diode arrangement without suffering from a decrease in light output or increase in forward voltage.
Furthermore, in the light emitting diode chip according to the present invention, a portion of the first electrode pad is disposed on the second extension, thereby enabling reduction in size of the inverse parallel diode section without reducing the size of the electrode pad. As a result, it is possible to prevent decrease in light emitting area of the light emitting diode section even when the inverse parallel diode section is formed.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A light emitting diode chip comprising:

a substrate;

a light emitting diode section disposed on the substrate; and

an inverse parallel diode section disposed on the substrate and connected inversely parallel to the light emitting diode section.

2. The light emitting diode chip of claim 1, further comprising a reflector covering at least a portion of the inverse parallel diode section.

3. The light emitting diode chip of claim 2, wherein the reflector comprises a distributed Bragg reflector.

4. The light emitting diode chip of claim 1, wherein the light emitting diode section and the inverse parallel diode section each comprise:

a first conductivity type nitride semiconductor layer;

a second conductivity type nitride semiconductor layer; and

an active layer disposed between the first conductivity type nitride semiconductor layer and the second conductivity type nitride semiconductor layer.

5. The light emitting diode chip of claim 4, further comprising:

a first electrode pad; and

a second electrode pad,

wherein the first electrode pad is disposed on the inverse parallel diode section, and the second electrode pad is disposed on the light emitting diode section.

6. The light emitting diode chip of claim 5, further comprising:

a first extension extending from the first electrode pad; and

a second extension extending from the second electrode pad,

wherein:

the first extension is electrically connected to the first conductivity type nitride semiconductor layer of the light emitting diode section; and

the second extension is electrically connected to the first conductivity type nitride semiconductor layer of the inverse parallel diode section.

7. The light emitting diode chip of claim 6, wherein a portion of the first electrode pad is disposed on the second extension.

8. The light emitting diode chip of claim 7, further comprising an insulation layer insulating the first electrode pad from the second extension.

9. The light emitting diode chip of claim 6, wherein the first extension is connected to the first conductivity type nitride semiconductor layer at a plurality of points on the light emitting diode section.

10. The light emitting diode chip of claim 9, wherein:

the first extension passes through an upper portion of the second conductivity type nitride semiconductor layer of the light emitting diode section; and

the first extension is electrically insulated from the second conductivity type nitride semiconductor layer by the insulation layer.

11. The light emitting diode chip of claim 6, further comprising a second transparent electrode layer disposed between the first electrode pad and the second conductivity type nitride semiconductor layer of the inverse parallel diode section.

12. The light emitting diode chip of claim 11, further comprising a first transparent electrode layer connected to an upper surface of the second conductivity type nitride semiconductor layer of the light emitting diode section,

wherein the second electrode pad is disposed on the first transparent electrode layer.

13. The light emitting diode chip of claim 12, further comprising a current blocking layer disposed under the first transparent electrode layer below the second electrode pad.

14. The light emitting diode chip of claim 11, further comprising a current blocking layer disposed under the first transparent electrode layer and below the second extension.

15. The light emitting diode chip of claim 14, wherein the current blocking layer comprises a distributed Bragg reflector.

16. The light emitting diode chip of claim 6, wherein the reflector covers at least a portion of the inverse parallel diode section.

17. The light emitting diode chip of claim 16, wherein at least a portion of the reflector extends to the light emitting diode section and is configured to insulate the second extension from a side surface of the light emitting diode section.

18. The light emitting diode chip of claim 16, wherein at least a portion of the reflector extends to the light emitting diode section and is configured to insulate the first extension from the light emitting diode section.

19. The light emitting diode chip of claim 16, wherein:

the reflector covers the inverse parallel diode section so as to enclose the first electrode pad; and

the reflector comprises an opening through which the first conductivity type nitride semiconductor layer connected to the second extension is exposed.

20. The light emitting diode chip of claim 6, wherein at least one of the first extension and the second extension comprises a reflective metal layer.

21. A light emitting diode chip comprising:

a substrate;

a light emitting diode section disposed on the substrate;

an inverse parallel diode section disposed on the substrate;

a first electrode pad disposed on the inverse parallel diode section;

a second electrode pad disposed on the light emitting diode section;

a first extension extending from the first electrode pad and connected to the light emitting diode section; and

a second extension extending from the second electrode pad and connected to the inverse parallel diode section,

wherein the inverse parallel diode section is connected inversely parallel to the light emitting diode section.

22. The light emitting diode chip of claim 21, further comprising a reflector disposed under at least a portion of the second extension.

23. A light emitting diode package comprising:

a chip mounting section having a chip mounting face; and

a light emitting diode chip mounted on the chip mounting face,

wherein the light emitting diode chip comprises:

a substrate;

a light emitting diode section disposed on the substrate; and

24. The light emitting diode package of claim 23, wherein the light emitting diode chip further comprises a reflector covering at least a portion of the inverse parallel diode section.