RU2535649C1 - Semiconductor laser - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: semiconductor laser includes a heterostructure grown on a GaAs substrate, restricted with end surfaces perpendicular to the growth axis, with coatings applied onto them, on one side - with a reflecting coating, and on the other one - with an anti-reflecting coating, and including a waveguide layer with an active region, the formed p-i-n-junction, a contact layer and restricting layers; deflection indices of the latter are lower than those of the substrate and other layers; the contact layer and the restricting layer adjacent to it are alloyed with acceptors, and the substrate and the other restricting layer are alloyed with donors. The heterostructure includes a GaAs buffer layer alloyed with donors and arranged between the substrate and the restricting layer, and the active region of the waveguide layer includes at least three quantum wells InGaAs, which are made in the p-i-n-junction formed with waveguide, buffer and restricting layers; besides, thicknesses of the waveguide layer and the restricting layer adjacent to the buffer layer are chosen so that there can be provided losses for radiation yield to the substrate in the range of 10-50 cm^-1 and angle φ of the radiation yield to the substrate in the range of 0-3°.

EFFECT: providing possible reduction of radiation divergence.

8 cl, 1 dwg

Description

The proposed invention relates to quantum electronic technology, relates to a semiconductor laser containing a heterostructure with an active zone, including several quantum wells in compounds of the type A3B5, and which can be used in fiber-optic communication systems, in the pump systems of solid-state lasers, in navigation systems, in medical equipment, etc.

In an injection laser with a strip active generation zone and radiation output through an optical resonator mirror [“Lasers on heterostructures” in 2 volumes, X. Casey, M. Panish, M., Mir, 1981, T. 1, 300 pp.] a layered heterostructure with an active zone is located between the vertical reflectors of the optical resonator. When a current flows through it, radiation is amplified, and under certain appropriate conditions, radiation is also generated. One of the mirrors of the optical resonator is partially transparent, and the used radiation comes out through it. In such a laser, there are only waveguide modes propagated along the axis of the optical resonator between its mirrors. In this case, the necessary measures are taken to exclude the occurrence of leakage radiation through the layers of the heterostructure into the substrate and the upper contact layer, since this reduces the efficiency of the laser devices. The size of the body of the glow in the direction perpendicular to the layers of the heterostructure, usually does not exceed several microns, and in the direction parallel to the layers of the heterostructure, is determined by the width of the stripe core. These lasers have the following disadvantages:

- high astigmatism of radiation due to the limited size of the body of the glow in the direction perpendicular to the layers of the heterostructure;

- violation of the single-mode lasing regime with a sharp increase in the divergence of the laser radiation with an increase in the width of the strip active region (in the typical case of a strip laser, this occurs if the strip width exceeds 3-6 μm);

- small areas of the luminous body, for which the diffraction divergence of radiation is ensured, limit the creation of a semiconductor laser with a high output radiation power and high reliability at the same time.

The creation of semiconductor radiation sources that preserve diffraction divergence with an increase in the size of its radiating surface, and hence the output radiation power, is one of the most important tasks of laser technology.

In the design of the laser according to the patent [RU 2142665C1, 10.12.1999, H01S 3/19], it is proposed to use at least one InGaAs quantum-well layer as an active medium with a band gap smaller than the band gap of the substrate (GaAs), which significantly reduces the absorption of radiation in the substrate. The formation of modes in the optical cavity of the laser occurs, for the most part, during the propagation of laser beams in a homogeneous, non-amplifying, weakly absorbing volume of the leak-in region (substrate) and only after the laser rays reflected from the optical faces fall into the amplification region and the total internal reflection of the rays at the boundary The inflowing regions with heterostructure layers with an active layer undergo local amplification. A laser may be called an injection laser (or diode laser) with a cavity resonator. The design of the laser in the patent provides for the tilt of at least one of the faces of the resonator, on which radiation is reflected and through which radiation is output to a nonzero angle ψ. However, the practical implementation of laser designs with a nonzero angle of inclination of the faces is difficult, especially if the angle ψ is sufficiently large.

The closest in technical essence and the achieved result to the proposed invention is a semiconductor laser protected by patent [US 4063189, 12/13/1977, H01S 3/19], adopted as the closest analogue (prototype). In the prototype, the amplification and formation of the corresponding modes of laser radiation occurs entirely in a thin, active, dielectric waveguide in the amplification region bounded by the end reflectors of the optical resonator. In this patent and article [D.R. Scifres, W Streifer, and R.D. Burnham, Applied Physics Letters (1976), v.29, N 1, pp.23-25] the same authors attempted to increase the output aperture and, accordingly, reduce the divergence angle and astigmatism in the direction perpendicular to the pin junction, for which an injection laser with leaky radiation was proposed. The design of the known injection laser according to US Pat. No. 4,063,189 consists of a substrate, a laser heterostructure (hereinafter referred to as a heterostructure), containing a waveguide layer with one active quantum well, placed between two optically uniform boundary layers. From the end faces, the laser heterostructure is bounded by end flat surfaces (chipped faces) that act as reflectors of the optical cavity and determine the length L of the optical cavity (Fabry-Perot). They are coated on one side with a reflective coating with a reflection coefficient close to unity, and on the other hand with an antireflection coating. On the surface of the boundary layer remote from the active layer, a radiation leak-in region (substrate) is placed. A contact layer is placed on the surface of the boundary layer of the heterostructure remote from the active layer and an ohmic contact is formed on it. On the opposite side, another ohmic contact is made on the outer surface of the substrate.

The active layer is chosen very thick, with a thickness d in the range of 0.1 ... 2 microns. The bounding layers are optically homogeneous; their refractive indices are less than the refractive index of the active layer. The boundary layer adjacent to the substrate is selected thin, namely 0.5-0.06 μm. The substrate has a refractive index greater than the refractive index of the boundary layer adjacent to it. The active layer and the substrate have the same composition — gallium arsenide semiconductor (GaAs), which determines a large absorption coefficient of the order of 30 cm ⁻¹ (see [DR Scifres, W Streifer, and RD Burnham, Applied Physics Letters (1976) ), v.29, N 1, pp.23-25]). The thickness W of the substrate is chosen to be much larger than the sum of the thicknesses of the active layer (d) and the optically homogeneous single layer boundary layer (b) adjacent to the substrate. The substrate is limited by chipped faces perpendicular to the active layer.

After applying bias to the pin junction, which is formed between, for example, the active layer and the bounding layer adjacent to the substrate, nonequilibrium carriers are injected into the active layer and radiation of a given wavelength and mode composition is generated in it. The operation of the laser in the leaky mode occurs under the condition that the boundary layer adjacent to the substrate is selected to be very thin so that part of the radiation propagates into the substrate and forms a leaky wave in it at a certain leakage angle φ to the pin junction, i.e. so that the condition for the emission of radiation into the substrate is realized. The authors of this patent obtained the following main parameters of the manufactured laser: the threshold current density is 7.7 kA / cm ² , the threshold current is 7 A with the diode size: length 400 μm, width 225 μm, substrate thickness 100 μm (up to 200 μm); the leakage angle φ is 3 °, the output power in a short pulse is about 3 W, the differential efficiency is about 35.4%, the divergence (angular width at half maximum of the radiation pattern in the far zone, shot in a plane perpendicular to the pin junction) 2 °. The advantage is the small divergence for the outgoing radiation output through the face with an antireflective coating, and the low radiation density on the output surface of the face, due to the large scale of localization of the electromagnetic field in the laser in a plane parallel to the faces.

However, the prototype has significant disadvantages: high threshold current density, which, at least, was twice as high compared to conventional non-leakage laser diodes, and low generated radiation power. This is due, among other things, to the choice of the same materials for the substrate with a large radiation absorption coefficient (of the order of 30 cm ^-1 cm) and the active layer, as well as the choice of the tilt angles (ψ = 0) of the resonator faces and the radiation exit angle (φ ~ 3 °) in the substrate. It is known that for high-power lasers, the cavity length should be sufficiently large, more than 2 mm [D.A. Vinokurov, A.L. Stankevich, V.V. Shamakhov, V.A. Kapitonov, A.Yu. Leshko, AB Lyutetskiy, D.N. Nikolaev, HA Pikhtin, HA Rudova, Z.N. Sokolova, S.O. Slipchenko, M.A. Khomylev, I.S. Tarasov. Semiconductor Physics and Technology (2006), Volume 40, Issue 6, pp. 764-767], and the radiation output circuit for the prototype assumes that with a substrate thickness of 200 μm and an exit angle φ ~ 3 ° of radiation into the substrate, the cavity length should not exceed 1.9 mm for good quality of the output radiation from the laser. For a longer resonator, half of the radiation emerging into the substrate at an angle φ in the direction of the almost completely reflective coating is reflected specularly from it and falls on the back side of the substrate (usually of non-optical quality), on which it diffuses diffusely on the irregularities of the back side of the substrate to a sufficiently wide angle and partially absorbed in the laser, and partially exits through the antireflection coating of the face with high divergence, which also affects the quality of the output radiation from the laser. Even the use of a substrate with optical quality on the reverse side will lead to the formation of another peak in the radiation pattern in the far zone, shot in a plane perpendicular to the pin junction, which affects the quality of the radiation emitted from the laser.

The objective of the invention is the creation of a semiconductor laser with a narrow radiation pattern in the far zone in a plane perpendicular to the p-i-n junction, with the output of radiation through a weakly absorbing substrate.

The technical result from the use of the invention is to reduce the divergence of radiation in a plane perpendicular to the p-i-n junction, increasing the power of laser radiation.

The specified technical result is achieved due to the fact that in a semiconductor laser containing features common with the prototype, namely:

a heterostructure grown on a gaAs substrate, bounded by end surfaces perpendicular to the growth axis, with coatings deposited on them, on the one hand reflective and on the other antireflective, and includes a waveguide layer with an active region, a formed pin junction, a contact layer, and bounding layers , the refractive indices of the latter are lower than the refractive indices of the substrate and other layers, the contact layer and the adjacent bounding layer are doped with acceptors, and the substrate and another bounding layer are doped to onors contain distinctive signs, namely:

- a GaAs buffer layer doped with donors and placed between the substrate and the bounding layer is included in the heterostructure;

- the active region of the waveguide layer is made with at least three InGaAs quantum wells;

- quantum wells are made in the p-i-n junction;

- p-i-n junction is formed by the waveguide, buffer and restrictive layers;

- the thickness of the waveguide layer and the boundary layer adjacent to the buffer are selected in such a way as to ensure losses in the radiation output to the substrate in the range of 10-50 cm ^-1 and the radiation exit angle φ in the substrate in the range of 0-3 °.

Besides:

- the degree of doping of the substrate with donors is less than 2 × 10 ¹⁸ cm ^-3 ;

- the degree of doping of the buffer layer corresponds to the degree of doping of the substrate;

- the degree of doping of the bounding layer adjacent to the buffer layer corresponds to the degree of doping of this buffer layer;

- the degree of doping of the boundary layer adjacent to the contact layer is 10 ¹⁸ -3 × 10 ¹⁸ cm ^-3 ;

- the degree of doping of the contact layer is 10 ¹⁹ -5 × 10 ¹⁹ cm ^-3 ;

- the number of quantum wells is proportional to the losses at the output of radiation into the substrate;

- on the end surface of the heterostructure from the side of placement of the antireflection coating, a reflective coating is applied, which is in contact with the antireflection and closes the contact waveguide and the boundary layers.

Figure 1 shows a diagram of the proposed semiconductor laser, where:

1 - GaAs substrate,

2 - buffer layer of GaAs,

3 - a restrictive layer of InGaP or AlGaAs,

4 - waveguide layer, the active region of which contains at least 3 InGaAs quantum wells, separated by GaAs or GaAsP barriers,

5 - contact layer of GaAs,

6 - almost completely reflective dielectric coating,

7 - antireflection dielectric coating.

Conventional lines with arrows show the directions of the outgoing radiation at the leakage angle φ inside the substrate 1 and the output radiation at the refraction angle δ outside the substrate 1. A semiconductor laser is a heterostructure grown on a substrate 1, which includes: a buffer layer 2, restrictive layers 3, a waveguide layer 4 (conductor), the active region of which contains at least three identical quantum wells, the contact layer 5. The active region with quantum wells is undoped and is made in a pin junction, formed th waveguide 4, a buffer 2 and 3 layers restrictive. The refractive indices of the waveguide region 4, the buffer layer 2 and the substrate 1 exceed the refractive indices of the bounding layers 3. The substrate 1 is doped with donors less than 2 * 10 ¹⁸ cm ^-3 . The buffer layer 2 is made with a degree of doping not less than the degree of doping of the substrate 1. The boundary layer 3 adjacent to the buffer layer 2 is doped with no less degree of doping than the buffer layer 2.

The restriction layer 3 adjacent to the buffer layer 2 is selected thin enough so that the loss of radiation output to the substrate is 10-50 cm ^-1 .

The boundary layer 3 adjacent to the contact layer 5 is doped with acceptors with a degree of 10 ¹⁸ -3 * 10 ¹⁸ cm ^-3 . The contact layer 5 is heavily doped, the degree of doping is, for example, 10 ¹⁹ -5 * 10 ¹⁹ cm ^-3 . The number of quantum wells in the waveguide layer 4 is proportional to the loss of radiation output to the substrate 1. Dielectric coatings are deposited on the chips perpendicular to the growth axis of the grown structure: on the one hand, coating 6, which almost completely reflects the radiation, on the other hand, antireflection coating 7, through which radiation is carried out. It is also possible to lower the generation threshold on a part of both faces bounding the restrictive 3, waveguide 4 and contact 5 layers, to apply a coating that almost completely reflects radiation 6. The thicknesses of the waveguide layer 4 and the restrictive layer 3 adjacent to the buffer layer 2 are selected in this way in order to ensure losses in the output of radiation into the substrate 1 in the range of 10-50 cm ^-1 , and the angle of radiation exit into the substrate 1 φ would lie in the range 0-3 °.

The following are examples of specific performance of the invention.

Example 1

The GaAs substrate was doped with donors up to 10 ¹⁸ cm ^-3 . The growth of the heterostructure was carried out by the method of MOS - hydride epitaxy at atmospheric pressure. A 540-nm-thick GaAs buffer layer with the same doping level was grown on the substrate to compensate for defects. Then, an InGaP bounding layer was grown with a thickness of 80 nm with the same degree of doping. Then, an undoped GaAs waveguide layer with a total thickness of 1818 nm was grown with 6 InGaAs quantum wells located at its center each 9 nm thick and separated by a three-layer GaAs / GaAsP / GaAs barrier, where each layer has a thickness of 36 nm. Then, an InGaP confinement layer was grown at a thickness of 432 nm doped with acceptors with a degree of 10 ¹⁸ cm ^–3 . The buffer, restrictive, and waveguide layers form a pin junction. Next, a GaAs contact layer doped with acceptors with a doping degree of 10 ¹⁹ cm ^–3 and a thickness of 216 nm grows next. For high-quality manufacturing of the resonator faces, the substrate was thinned by chemical etching to a thickness of 150 μm. Laser diodes with an active region width of 360 μm and a cavity length of 1 mm were fabricated by chemical etching of the contact layer outside the active strip, followed by proton implantation of the exposed InGaP surface. After making contacts and cracking, the chips were soldered onto the copper heat sinks with the structure down to operate the lasers in the continuous and pulsed generation mode. The antireflection and reflective coatings were deposited onto the output faces of a semiconductor laser by electron beam evaporation. The reflective coating had a reflection coefficient R ~ 0.98, and the antireflection coating R ~ 0.06. The following main parameters of the manufactured laser were obtained at a temperature of 290 K: the threshold current density is 1.6 kA / cm ² , the leakage angle φ is 2.85 °, the output power in a short pulse with a duration of 5 μs is about 34 W, the differential efficiency is about 30%, the divergence is 2 °, radiation wavelength of 977 nm.

Example 2

The GaAs substrate was doped with donors up to 5 × 10 ¹⁷ cm ^-3 . The growth of the heterostructure was carried out by the method of MOS-hydride epitaxy at atmospheric pressure. A 900 nm thick GaAs buffer layer with a doping degree of 1.6 × 10 ¹⁸ cm ^{–3 was} grown on a substrate for compensating defects. Then, a 56-nm-thick InGaP boundary layer was grown with the same doping level. Then, an undoped GaAs waveguide layer with a total thickness of 1656 nm was grown with 6 InGaAs quantum wells located at its center each 10 nm thick and separated by a three-layer GaAs / GaAsP / GaAs barrier, where the thickness of the GaAs layers in the barrier was 40 nm and the thickness of the GaAsP layer in the barrier - 30 nm. Then, an InGaP restriction layer was grown with a thickness of 420 nm, doped with acceptors with a degree of 3 * 10 ¹⁸ cm ^-3 . The buffer, restrictive, and waveguide layers form a pin junction. Next, a GaAs contact layer doped with acceptors with a doping degree of 10 ¹⁹ cm ^-3 and a thickness of 210 nm grows next. For high-quality manufacturing of the resonator faces, the substrate was thinned by chemical etching to a thickness of 150 μm. Laser diodes with an active region width of 360 μm and a cavity length of 1 mm were fabricated by chemical etching of the contact layer outside the active strip, followed by proton implantation of the exposed InGaP surface. After making contacts and cracking, the chips were soldered onto the copper heat sinks with the structure down to operate the lasers in the continuous and pulsed generation mode. The antireflection and reflective coatings were deposited onto the output faces of a semiconductor laser by electron beam evaporation. The reflective coating had a reflection coefficient R ~ 0.98, and the antireflection coating R ~ 0.06. The following main parameters of the manufactured laser were obtained at a temperature of 290 K: the threshold current density is 1.6 kA / cm ² , the leakage angle φ is 2.7 °, the output power in a short pulse with a duration of 5 μs is about 56 W, the differential efficiency is about 30%, the divergence is 2 °. radiation wavelength 1020 nm.

The assembly of the invention is as follows.

A heterostructure for a semiconductor laser is grown by the methods of MOS hydride or molecular beam epitaxy in the following sequence: growth of layers 2, 3, 4, 3, 5 on substrate 1. A buffer layer 2 with a degree of doping of at least the degree of doping of substrate 1 is grown to compensate for defects. Then, layers are grown with a pin junction formed by an undoped waveguide region 4 with active quantum wells, buffer 2, and bounding 3 layers. Then a highly alloyed contact layer 5 is grown. For current-pumped lasers, metal contacts are made to the back of the substrate 1 and to the contact layer 5. The mirrors are chipped faces coated with dielectric coatings 6, 7. On one of the faces, coated 6 increases the coefficient reflection, and on the other, coating 7 reduces the reflection coefficient. It is also possible to lower the threshold of generation on a part of the faces bounding the restrictive 3, waveguide 4 and contact 5 layers, to apply a coating 6, which almost completely reflects the radiation. To increase the gain and, accordingly, the power of laser radiation, the number of quantum wells should be proportional to the loss of radiation output to the substrate. The thicknesses of the waveguide layer 4 and the bounding layer 3 adjacent to the buffer layer 2 are selected in such a way as to ensure losses on the output of radiation into the substrate 1 in the range of 10-50 cm ^-1 , and the angle of exit of radiation into the substrate 1 φ was in the range 0-3 °. It is known from [patent RU 2142665] that a necessary condition for radiation to escape into the substrate 1 is to fulfill the relation (n _sub is the refractive index of the substrate):

$$n_{eff}<n_{sub},\left(\mathrm{one}\right)$$

where the effective refractive index n _eff can be obtained by calculation from the relation β = (2π / λ) n _eff , where β is the modulus of the complex value of the propagation constant of the amplified radiation wave in the direction along the longitudinal axis located in the waveguide layer 4, and λ - wavelength of radiation. The value of β can be determined by knowing the thicknesses and refractive indices of all layers [“Lasers on heterostructures” in 2 volumes, X. Casey, M. Panish, M., Mir, 1981, Vol. 1, 300 pp.]. When condition (1) is fulfilled, the amplification of the guided modes in the waveguide layer 4 of the proposed laser decreases and the radiation intensity increases in the form of waves flowing at the leakage angle φ to the plane of the waveguide layer 4, equal to:

$$\phi =\arccos \left(n_{eff}/n_{sub}\right).\left(2\right)$$

The output of the resulting laser radiation occurs after at least one refraction of it on the edges of the laser. The angle of refraction of the output radiation on the edge of the laser is equal to:

$$\delta =\arcsin \left(n_{sub}\sin \varphi \right).\left(3\right)$$

It is known that for high-power lasers, the cavity length should be sufficiently large [D.A. Vinokurov, A.L. Stankevich, V.V. Shamakhov, V.A. Kapitonov, A.Yu. Leshko, A.B. Lutetskiy, D.N. Nikolaev, H.A. Pikhtin, H.A. Rudova, Z.N. Sokolova, S.O. Slipchenko, M.A. Khomylev, I.S. Tarasov. Physics and Engineering of Semiconductors (2006), Volume 40, Issue 6, pp. 764-767]. The expression for the maximum laser length L, which is possible without re-reflection from the back of the substrate 1, can be written in the following form:

$$L=0.5Wctg\varphi ,\left(\mathrm{four}\right)$$

where W is the thickness of the substrate 1, the maximum thickness of which usually does not exceed 200 microns. It follows from formula (4) that the length L can be increased by decreasing the angle φ, which can be achieved by choosing the thickness of the waveguide layer 4 and the boundary layer 3 adjacent to the buffer layer 2 so that n _eff → n _sub .

In the proposed semiconductor laser, the activity of the medium (quantum wells in the waveguide region 4) is created due to the inverse distribution of electrons between the levels of dimensional quantization of the valence band and the conduction band. The large concentration of electrons and holes necessary for inversion can be created by injection in the p-i-n junction (current pumping). The active medium must be coupled to the resonator (waveguide with mirrors) and feedback is carried out between them. When the gain in wave energy due to interaction with the active region (gain) becomes equal to the total loss (including the output of radiation from the resonator), the device turns into a source of coherent electromagnetic radiation (laser).

For the proposed semiconductor laser, the divergence of radiation in a plane perpendicular to the p-i-n junction is possible in the angular range of 1-2 degrees, depending on the transverse size and the fraction of radiation flowing into the substrate 1. The transverse size, fraction and exit angle φ of the radiation flowing out into the substrate 1 can be controlled by changing the thickness of the substrate 1 and the waveguide layer 4, the thickness and composition of the bounding layer 3 adjacent to the buffer 2. An increase in the thickness of the substrate 1 leads to an increase in the transverse size of the flowing into the substrate 1 radiation. By reducing the thickness of the waveguide layer 4 and / or the bounding layer 3 adjacent to the buffer 2, it is possible to increase the proportion of radiation flowing into the substrate 1. By decreasing the proportion of aluminum (if the boundary layer consists of AlGaAs) in the composition of the layer of the boundary layer 3 adjacent to the buffer 2, it is also possible to increase the fraction of radiation flowing into the substrate 1. By increasing the thickness of the waveguide layer 4, it is possible to reduce the exit angle φ of the radiation flowing into the substrate 1. The ability to achieve small divergence of radiation in a plane perpendicular to the p-i-n junction gives a significant gain due to the absence or alleviation of the problem of focusing radiation when used in various devices. A decrease in the exit angle φ of the radiation flowing into the substrate 1 makes it possible to create powerful efficient lasers with a long cavity length.

The proposed design easily implements a single-mode transverse radiation output to the substrate 1, regardless of the thickness of the substrate, which is associated with large losses for the excitation of the next mode flowing into the substrate 1, and which is important for creating high-power semiconductor lasers with a narrow radiation pattern.

Thus, the proposed semiconductor laser allows you to get a narrow radiation pattern in the far zone, in a plane perpendicular to the p-i-n junction, with the output of the radiation through a weakly absorbing substrate. Using the proposed semiconductor laser provides a decrease in the divergence of radiation in a plane perpendicular to the p-i-n junction, and an increase in the power of laser radiation.

In addition, the laser has a high potential for its production in industry, since standard, highly reproducible technological operations developed to create systems based on A3B5 compounds and their solid solutions are used for the manufacture of devices.

Claims (8)

1. A semiconductor laser containing a heterostructure grown on a GaAs substrate, bounded by end surfaces perpendicular to the growth axis, with coatings deposited on them, on the one hand reflective and on the other antireflective, and including a waveguide layer with an active region, a formed pin junction , the contact layer and the bounding layers, the refractive indices of the latter are smaller than the refractive indices of the substrate and other layers, the contact layer and the adjacent bounding layer are doped with acceptors, and the substrate and other the boundary layer is doped with donors, characterized in that the heterostructure includes a GaAs buffer layer doped with donors and placed between the substrate and the boundary layer, and the active region of the waveguide layer contains at least three InGaAs quantum wells made in a pin junction formed by waveguide, buffer and restrictive layers, in addition, the thickness of the waveguide layer and adjacent to the buffer restrictive layer are selected in such a way as to provide losses on the output of radiation into the substrate in the range of 10-50 s m ^-1 and the angle of exit of radiation into the substrate φ in the range of 0-3 °. 2. The semiconductor laser according to claim 1, characterized in that the degree of doping of the substrate with donors is less than 2 × 10 ¹⁸ cm ^-3 . 3. The semiconductor laser according to claim 1, characterized in that the degree of doping of the buffer layer corresponds to the degree of doping of the substrate. 4. The semiconductor laser according to claim 1, characterized in that the degree of doping of the bounding layer adjacent to the buffer layer corresponds to the degree of doping of this buffer layer. 5. The semiconductor laser according to claim 1, characterized in that the degree of doping of the bounding layer adjacent to the contact layer is 10 ¹⁸ -3 × 10 ¹⁸ cm ^-3 . 6. The semiconductor laser according to claim 1, characterized in that the degree of doping of the contact layer is 10 ¹⁹ -5 × 10 ¹⁹ cm ^-3 . 7. The semiconductor laser according to claim 1, characterized in that the number of quantum wells is proportional to the loss of radiation output to the substrate. 8. The semiconductor laser according to claim 1, characterized in that on the end surface of the heterostructure from the side of placement of the antireflection coating, a reflective coating is applied, which is in contact with the antireflection and closes the contact waveguide and bounding layers.