A buried heterostructure antimonide laser and a method of fabricating the same

Abstract

The application provides a buried heterojunction antimonide laser and a preparation method thereof, and belongs to the technical field of lasers. The problems of a relatively high threshold current, a limited transverse restriction of current and light field, and a single heat dissipation path of a conventional ridge waveguide structure are solved. The laser comprises, from bottom to top, N-face metal, a GaSb substrate, a buffer layer, a lower restriction layer, a lower waveguide layer, a quantum well region, an upper waveguide layer, an upper restriction layer, a cover layer and P-face metal. A ridge is arranged between the P-face metal and the restriction layer, and buried layers are arranged on both sides of the ridge. In the application, the active region is completely wrapped from the side by using a wide-bandgap, low-refractive-index, lattice-matched semiconductor material through secondary epitaxy, the physical properties of the material itself are used to achieve better three-dimensional restriction of current and light field, and thus lower threshold current, higher output power, better mode stability and longer device life are obtained.

Description

Technical Field

[0001] This application relates to the field of laser technology, and in particular to a buried heterojunction antimonide laser and its preparation method. Background Technology

[0002] The rapid development of high-tech fields such as optical communication, quantum information, and artificial intelligence is driving the iteration of semiconductor technology towards fourth-generation semiconductor technology, characterized by high performance, low power consumption, and low cost, while simultaneously propelling the development of next-generation semiconductor materials. Antimony semiconductor materials, composed of multi-component compound materials based on group III-V elements such as Al, Ga, In, As, and Sb, and their low-dimensional structures, are among the most promising fourth-generation semiconductor materials. Based on their narrow bandgap, natural lattice matching, and tunable band structure, antimony semiconductor materials will play a significant role in the development of next-generation infrared optoelectronic systems. Antimony lasers, as important infrared optoelectronic devices, have achieved room-temperature continuous operation of a series of high-performance antimony quantum well lasers through breakthroughs in band structure design, epitaxial growth, and device fabrication processes. These lasers can cover the entire short-wave infrared to mid-infrared band and have significant application value in many important fields such as gas detection, medical aesthetics, next-generation communication windows, and quantum communication.

[0003] Antimonide lasers are mainly classified into type I quantum well lasers and interband cascaded lasers. For the 2-3µm wavelength range, InGa(As)Sb-AlGaAsSb type I strained quantum wells exhibit certain advantages. These are epitaxially mounted on commercial GaSb substrates, using InGa(As)Sb as the quantum well, low-Al content AlGaAsSb as the quantum barrier and waveguide layer, and high-Al content AlGaAsSb as the confinement layer, thus achieving dual confinement of light and electricity to ensure high-quality laser lasing. Currently, the mainstream antimonide laser structure is a ridge waveguide structure, where ridges are formed by etching the material, and then an insulating dielectric film is deposited on the sidewalls to achieve lateral confinement of current and optical field.

[0004] Ridge waveguide lasers are relatively simple to design, have mature manufacturing processes, low cost, high yield, are applicable to almost all material systems, and offer good reliability. Their disadvantages lie in their relatively high threshold current, and the need for further improvement in the lateral confinement of current and optical field. More importantly, the heat dissipation path of ridge waveguide lasers is relatively singular (only vertical), and the poor thermal conductivity of the dielectric film leads to earlier thermal saturation, thus limiting further increases in laser power. Summary of the Invention

[0005] To address the aforementioned technical problems, this application proposes a buried heterojunction antimonide laser and its fabrication method.

[0006] The technical solution adopted in this application is as follows: a buried heterojunction antimonide laser, comprising, from bottom to top, an N-plane metal, a GaSb substrate, a buffer layer, a lower confinement layer, a lower waveguide layer, a quantum well region, an upper waveguide layer, an upper confinement layer, a capping layer, and a P-plane metal, wherein a ridge is provided between the P-plane metal and the confinement layer, and a buried layer is provided on both sides of the ridge, and the buried layer adopts an AlGaAsSb material system that matches the GaSb crystal lattice.

[0007] Furthermore, a ridge is provided between the P-side metal and the upper confinement layer.

[0008] Furthermore, a ridge is provided between the P-side metal and the lower confinement layer.

[0009] Furthermore, the width of the ridge is from 1µm to 250µm.

[0010] Furthermore, the GaSb substrate exhibits N-type conductivity with a carrier concentration of 5E16-1E18 cm⁻¹. -3 The thickness d1 is 500±25um; The buffer layer is made of GaSb material, with an N-type conductivity and a carrier concentration of 6E17-3E18 cm⁻¹. -3 The thickness d2 is 300-600nm.

[0011] Furthermore, the lower confinement layer is selected from Al. x1 Ga 1-x1 As z1 Sb 1-z1 The material has a 0.45 ≤ x1 ≤ 0.90 , and the choice of z1 should satisfy Al x1 Ga 1-x1 As z1 Sb 1-z1 It is lattice-matched with GaSb, with a thickness d3 of 1000-2500 nm, an N-type conductivity, and a carrier concentration of 3E17-1E18 cm⁻¹. -3 ; Al is selected for the lower waveguide layer x2 Ga 1-x2-y2 In y2 As z2 Sb 1-z2 Given materials, 0.20 ≤ x² ≤ 0.35, 0 ≤ y² ≤ 0.35, and the choice of z² should satisfy Al. x2 Ga 1-x2-y2 In y2 As z2 Sb 1-z2 It is lattice-matched with the GaSb substrate, with a thickness d4 of 100-1000 nm, and is not intentionally doped.

[0012] Furthermore, the quantum well in the quantum well region is selected from In x3 Ga 1-x3 As z3 Sb 1-z3 Materials: 0 ≤ x3 ≤ 0.60, x3 and z3 are selected based on wavelength and strain; the thickness of each well is 6-16 nm, unintentionally doped; the quantum barrier is made of Al lattice-matched to GaSb. x4 Ga 1-x4-y4 In y4 As z4 Sb 1-z4 The material has a thickness of 15-50 nm, is unintentionally doped, and has 1-5 quantum wells.

[0013] Furthermore, the upper waveguide layer is made of Al. x5 Ga 1-x5-y5 In y5 As z5 Sb 1-z5 The material has the following properties: 0.20 ≤ x5 ≤ 0.35, 0 ≤ y5 ≤ 0.35, where z5 is chosen to ensure that Al x5 Ga 1-x5-y5 In y5 As z5 Sb 1-z5 It is lattice-matched with GaSb substrates, with a thickness d6 of 100-1000 nm, and is not intentionally doped; The upper confinement layer is selected from Al. x6 Ga 1-x6 As z6 Sb 1-z6 For the material, 0.45 ≤ x6 ≤ 0.90, where the choice of z6 should ensure that Al x6 Ga 1-x6 As z6 Sb 1-z6 It is lattice-matched with GaSb, with a thickness d7 of 1000-2500 nm, exhibits p-type conductivity, and has a carrier concentration of 5E17-3E18 cm⁻¹. -3 ; The capping layer is made of GaSb material with a thickness d8 of 200-300 nm, a P-type conductivity, and a carrier concentration of 6E18-1E19 cm⁻¹. -3 .

[0014] Furthermore, the burial layer is made of Al. x7 Ga 1-x7 As z7 Sb 1-z7 The material has the following properties: 0.70 ≤ x7 ≤ 1.0, x7 – x6 ≥ 0.15, and x7 – x1 ≥ 0.15. The choice of z7 should satisfy the condition that Al... x7 Ga 1-x7 As z7 Sb1-z7 Matching the GaSb lattice, the thickness is from d_etch+300nm to d_etch+1000nm, unintentionally doped; where d_etch is the ridge etching depth, d_etch is from (d8+d7-700)nm to (d8+d7+d6+d4+d3)nm.

[0015] A method for fabricating a buried heterojunction antimonyide laser, characterized by comprising the following steps: S1: The first epitaxial growth is performed in a molecular beam epitaxy device: starting from the buffer layer, the lower confinement layer, the lower waveguide layer, the quantum well region, the upper waveguide layer, the upper confinement layer, and the capping layer are grown sequentially to obtain a device with a preliminary epitaxial layer. S2: Ridge fabrication: Based on the ridge width, ridge patterns are formed using photolithography or electron beam lithography; then, the ridge structure is fabricated on the device surface using dry or wet etching. S3: Second epitaxial growth, including: (1) After cleaning the device, blow it dry with nitrogen and put it into the sample inlet chamber of the molecular beam epitaxy equipment. Then, evacuate and degas it. (2) After multi-stage degassing and plasma cleaning, it is transferred to the growth chamber and gradually increased to the growth temperature under antimony protection to begin epitaxial growth; (3) Growth of buried layers; S4: Component fabrication, including: (1) Planarization and windowing: The device surface is flattened by chemical mechanical polishing; the capping layer area on the ridge is exposed by photolithography or electron beam exposure combined with etching process; (2) Evaporate the P-side metal to fabricate the P-side electrode; (3) Grinding and polishing to reduce thickness, evaporating N-side metal, and fabricating N-side electrodes; (4) Dissociation, coating, and sintering are used to obtain the final laser.

[0016] The advantages of this application compared to existing technologies are as follows: This application utilizes high-quality secondary epitaxy to completely encapsulate the active region from the side using a wide-bandgap, low-refractive-index, lattice-matched antimonybide semiconductor material. By leveraging the material's inherent physical properties (pn junction barrier, refractive index difference), it achieves better three-dimensional confinement of current and optical field, resulting in lower threshold current, higher output power, better mode stability, and longer device lifetime. Furthermore, compared to the dielectric passivation film used in conventional ridge waveguides, the buried layer of this application, based on an AlGaAsSb material system, can match the ridge lattice, providing more pathways for ridge heat dissipation and thus improving heat dissipation performance. Attached Figure Description

[0017] The following description, in conjunction with the accompanying drawings, further illustrates this application: Figure 1 This is a schematic diagram of a conventional ridge waveguide laser. Figure 2 A schematic diagram of the structure of the buried heterojunction antimonide laser provided in the embodiments of this application. Figure 1 ; Figure 3 A schematic diagram of the structure of the buried heterojunction antimonide laser provided in the embodiments of this application. Figure 2 ; Figure 4 A flowchart illustrating the fabrication process of a buried heterojunction antimonide laser provided in this application embodiment; In the figure: 1 is the N-plane metal, 2 is the GaSb substrate, 3 is the buffer layer, 4 is the lower confinement layer, 5 is the lower waveguide layer, 6 is the quantum well region, 7 is the upper waveguide layer, 8 is the upper confinement layer, 9 is the capping layer, 10 is the dielectric passivation film, 11 is the P-plane metal, and 12 is the buried layer. Detailed Implementation

[0018] like Figures 2 to 4 As shown, this application provides a buried heterojunction antimonide laser, comprising, from bottom to top, an N-plane metal 1, a GaSb substrate 2, a buffer layer 3, a lower confinement layer 4, a lower waveguide layer 5, a quantum well region 6, an upper waveguide layer 7, an upper confinement layer 8, a capping layer 9, and a P-plane metal 11, wherein a ridge is provided between the P-plane metal 11 and the confinement layer, and symmetrical buried layers 12 are provided on both sides of the ridge, and the width of the ridge is from 1 μm to 250 μm.

[0019] The GaSb substrate 2 has an N-type conductivity and a carrier concentration of 5E16-1E18 cm⁻¹. -3 The thickness d1 is 500±25um.

[0020] Buffer layer 3 is made of GaSb material, with an N-type conductivity and a carrier concentration of 6E17-3E18 cm⁻¹. -3 The thickness d2 is 300-600nm.

[0021] Lower confinement layer 4 uses Al x1 Ga 1-x1 As z1 Sb 1-z1 The material has a 0.45 ≤ x1 ≤ 0.90 , and the choice of z1 should satisfy Al x1 Ga 1-x1 As z1 Sb 1-z1 It is lattice-matched with GaSb, with a thickness d3 of 1000-2500 nm. Its conductivity type is N-type, and the carrier concentration is 3E17-1E18 cm⁻¹. -3 .

[0022] Lower waveguide layer 5 uses Al x2 Ga1-x2-y2 In y2 As z2 Sb 1-z2 Given materials, 0.20 ≤ x² ≤ 0.35, 0 ≤ y² ≤ 0.35, and the choice of z² should satisfy Al. x2 Ga 1-x2-y2 In y2 As z2 Sb 1-z2 Lattice-matched to GaSb substrate, thickness d4 is 100-1000 nm. Unintentional doping.

[0023] The quantum well in quantum well region 6 is selected from In x3 Ga 1-x3 As z3 Sb 1-z3 Material composition: 0 ≤ x3 ≤ 0.60, with x3 and z3 selected based on wavelength and strain (target wavelength range 1.9 to 3.3 μm); each well has a thickness of 6-16 nm and is unintentionally doped. Al is used as the quantum barrier. x4 Ga 1-x4-y4 In y4 As z4 Sb 1-z4 Material (lattice-matched to GaSb), 15-50 nm thick, unintentionally doped. Number of quantum wells: 1-5.

[0024] Upper waveguide layer 7 uses Al x5 Ga 1-x5-y5 In y5 As z5 Sb 1-z5 The material has the following properties: 0.20 ≤ x5 ≤ 0.35, 0 ≤ y5 ≤ 0.35, where z5 is chosen to ensure that Al x5 Ga 1-x5-y5 In y5 As z5 Sb 1-z5 Lattice-matched to GaSb substrate, thickness d6 is 100-1000 nm. Unintentional doping.

[0025] Upper confinement layer 8 uses Al x6 Ga 1-x6 As z6 Sb 1-z6 For the material, 0.45 ≤ x6 ≤ 0.90, where the choice of z6 should ensure that Al x6 Ga 1-x6 As z6 Sb 1-z6 It is lattice-matched with GaSb, with a thickness d7 of 1000-2500 nm. Its conductivity type is p-type, and the carrier concentration is 5E17-3E18 cm⁻¹. -3 .

[0026] Capping layer 9 is made of GaSb material with a thickness d8 of 200-300 nm, a P-type conductivity, and a carrier concentration of 6E18-1E19 cm⁻¹. -3 .

[0027] The buried layer 12 is made of Al. x7 Ga 1-x7 As z7 Sb 1-z7 The material has the following properties: 0.70 ≤ x7 ≤ 1.0, x7 – x6 ≥ 0.15, and x7 – x1 ≥ 0.15. The choice of z7 should satisfy the condition that Al... x7 Ga 1-x7 As z7 Sb 1-z7 Lattice-matched to GaSb. Thickness from d_etch+300nm to d_etch+1000nm. Unintentionally doped. Where d_etch is the ridge etching depth, ranging from (d8+d7-700)nm to (d8+d7+d6+d4+d3)nm.

[0028] Due to the different etching depths of the ridges, the buried layer 12 can have two different schemes.

[0029] like Figure 2 As shown, the buried layer 12 is disposed between the P-face metal 11 and the upper limiting layer 8, that is, the upper end of the buried layer 12 extends into the P-face metal 11, and the lower end of the buried layer 12 extends into the upper limiting layer 8.

[0030] like Figure 3 As shown, the buried layer 12 is disposed between the P-face metal 11 and the lower limiting layer 4, that is, the upper end of the buried layer 12 extends into the P-face metal 11, and the lower end of the buried layer 12 extends into the lower limiting layer 4.

[0031] This application also proposes a method for fabricating a buried heterojunction antimonide laser, such as... Figure 4 As shown, the method mainly includes the following steps: S1: The first epitaxial growth is performed in a molecular beam epitaxy (MBE) apparatus. Starting from the buffer layer 3, the lower confinement layer 4, the lower waveguide layer 5, the quantum well region 6, the upper waveguide layer 7, the upper confinement layer 8, and the capping layer 9 are grown sequentially to obtain a device with a preliminary epitaxial layer.

[0032] S2: Ridge Fabrication: Based on the ridge width (1µm to 250µm), ridge patterns are formed using photolithography or electron beam lithography (using photoresist, electron beam resist, silicon oxide, or silicon nitride as a mask). Then, dry or wet etching is used to fabricate the ridge structure on the device surface.

[0033] S3: Second epitaxial growth, including: (1) After cleaning the device, blow it dry with nitrogen and put it into the sample injection chamber of MBE. Then, evacuate and degas it. (2) After multi-stage degassing and plasma cleaning, it is transferred to the growth chamber and gradually increased to the growth temperature under antimony protection to begin epitaxial growth; (3) Growth of buried layer 12.

[0034] S4: Component fabrication, including: (1) Planarization and windowing: The device surface is flattened by chemical mechanical polishing; the capping layer 9 area on the ridge is exposed by photolithography or electron beam exposure plus etching and other processes; (2) Evaporate P-side metal 11 to fabricate P-side electrodes; (3) Grind and polish to thin, evaporate N-side metal 1, and fabricate N-side electrode; (4) Dissociation, coating, sintering, etc.

[0035] The buried layer 12 in this application has a significant refractive index difference with the ridge material, which can confine the optical field and reduce the threshold current. Furthermore, the sidewalls of the ridge in this application are steep or nearly steep straight lines (due to process variations, the angle between the sidewalls of the ridge and the active region is between 90-100°). These steep sidewalls create abrupt refractive index boundaries, providing strong lateral optical field confinement; they also correspond to clearly defined vertical current channels and carrier confinement regions. In summary, the steep sidewalls provide stronger carrier confinement of the optical field, which is beneficial for improving laser performance.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A buried heterojunction antimony compound laser, characterized in that: The structure includes, from bottom to top, an N-plane metal, a GaSb substrate, a buffer layer, a lower confinement layer, a lower waveguide layer, a quantum well region, an upper waveguide layer, an upper confinement layer, a capping layer, and a P-plane metal. A ridge is provided between the P-plane metal and the confinement layer, and buried layers are provided on both sides of the ridge. The buried layers adopt an AlGaAsSb material system that matches the GaSb lattice.

2. The buried heterojunction antimonyide laser according to claim 1, characterized in that: A ridge is provided between the P-side metal and the upper confinement layer.

3. A buried heterojunction antimonide laser according to claim 1, characterized in that: A ridge is provided between the P-side metal and the lower confinement layer.

4. A buried heterojunction antimonide laser according to claim 2 or 3, characterized in that: The width of the ridge strips ranges from 1µm to 250µm.

5. A buried heterojunction antimonide laser according to claim 1, characterized in that: The GaSb substrate exhibits N-type conductivity with a carrier concentration of 5E16-1E18 cm⁻¹. -3 The thickness d1 is 500±25um; The buffer layer is made of GaSb material, with an N-type conductivity and a carrier concentration of 6E17-3E18 cm⁻¹. -3 The thickness d2 is 300-600nm.

6. A buried heterojunction antimonyide laser according to claim 5, characterized in that: The lower confinement layer is selected from Al x1 Ga 1-x1 As z1 Sb 1-z1 The material has a 0.45 ≤ x1 ≤ 0.90 , and the choice of z1 should satisfy Al x1 Ga 1-x1 As z1 Sb 1-z1 It is lattice-matched with GaSb, with a thickness d3 of 1000-2500 nm, an N-type conductivity, and a carrier concentration of 3E17-1E18 cm⁻¹. -3 ; Al is selected for the lower waveguide layer x2 Ga 1-x2-y2 In y2 As z2 Sb 1-z2 Given materials, 0.20 ≤ x² ≤ 0.35, 0 ≤ y² ≤ 0.35, and the choice of z² should satisfy Al. x2 Ga 1-x2-y2 In y2 As z2 Sb 1-z2 It is lattice-matched with the GaSb substrate, with a thickness d4 of 100-1000 nm, and is not intentionally doped.

7. A buried heterojunction antimonide laser according to claim 6, characterized in that: Quantum wells in the quantum well region are selected using In x3 Ga 1-x3 As z3 Sb 1-z3 Materials: 0 ≤ x3 ≤ 0.60, x3 and z3 are selected based on wavelength and strain; the thickness of each well is 6-16 nm, unintentionally doped; the quantum barrier is made of Al lattice-matched to GaSb. x4 Ga 1-x4-y4 In y4 As z4 Sb 1-z4 The material has a thickness of 15-50 nm, is unintentionally doped, and has 1-5 quantum wells.

8. A buried heterojunction antimonide laser according to claim 7, characterized in that: The upper waveguide layer is made of Al x5 Ga 1-x5-y5 In y5 As z5 Sb 1-z5 The material has the following properties: 0.20 ≤ x5 ≤ 0.35, 0 ≤ y5 ≤ 0.35, where z5 is chosen to ensure that Al x5 Ga 1-x5-y5 In y5 As z5 Sb 1-z5 It is lattice-matched with GaSb substrates, with a thickness d6 of 100-1000 nm, and is not intentionally doped; The upper confinement layer is selected from Al x6 Ga 1-x6 As z6 Sb 1-z6 For the material, 0.45 ≤ x6 ≤ 0.90, where the choice of z6 should ensure that Al x6 Ga 1-x6 As z6 Sb 1-z6 It is lattice-matched with GaSb, with a thickness d7 of 1000-2500 nm, exhibits p-type conductivity, and has a carrier concentration of 5E17-3E18 cm⁻¹. -3 ; The capping layer is made of GaSb material with a thickness d8 of 200-300 nm, a P-type conductivity, and a carrier concentration of 6E18-1E19 cm⁻¹. -3 .

9. A buried heterojunction antimonide laser according to claim 8, characterized in that: Al is selected as the burial layer x7 Ga 1-x7 As z7 Sb 1-z7 The material has the following properties: 0.70 ≤ x7 ≤ 1.0, x7 – x6 ≥ 0.15, and x7 – x1 ≥ 0.

15. The choice of z7 should satisfy the condition that Al... x7 Ga 1-x7 As z7 Sb 1-z7 Matching the GaSb lattice, the thickness is from d_etch+300nm to d_etch+1000nm, unintentionally doped; where d_etch is the ridge etching depth, d_etch is from (d8+d7-700)nm to (d8+d7+d6+d4+d3)nm.

10. A method for preparing a buried heterojunction antimonide laser as described in any one of claims 1-9, characterized in that: Includes the following steps: S1: The first epitaxial growth is performed in a molecular beam epitaxy device: starting from the buffer layer, the lower confinement layer, the lower waveguide layer, the quantum well region, the upper waveguide layer, the upper confinement layer, and the capping layer are grown sequentially to obtain a device with a preliminary epitaxial layer. S2: Ridge fabrication: Based on the ridge width, ridge patterns are formed using photolithography or electron beam lithography; then, the ridge structure is fabricated on the device surface using dry or wet etching. S3: Second epitaxial growth, including: (1) After cleaning the device, blow it dry with nitrogen and put it into the sample inlet chamber of the molecular beam epitaxy equipment. Then, evacuate and degas it. (2) After multi-stage degassing and plasma cleaning, it is transferred to the growth chamber and gradually increased to the growth temperature under antimony protection to begin epitaxial growth; (3) Growth of buried layers; S4: Component fabrication, including: (1) Planarization and windowing: The device surface is flattened by chemical mechanical polishing; the capping layer area on the ridge is exposed by photolithography or electron beam exposure combined with etching process; (2) Evaporate the P-side metal to fabricate the P-side electrode; (3) Grinding and polishing to reduce thickness, evaporating N-side metal, and fabricating N-side electrodes; (4) Dissociation, coating, and sintering are used to obtain the final laser.

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