A vertical cavity surface emitting laser based on a composite metal substrate and a photonic crystal

Abstract

The application relates to the field of semiconductor lasers and discloses a vertical cavity surface emitting laser based on a composite metal substrate and a photonic crystal, which comprises, from bottom to top, a CIC composite metal substrate, a GaAs buffer layer, a lower n-type DBR, an n-type contact layer, a multi-junction cascade active region, a p-type contact layer and an upper p-type DBR; a plurality of two-dimensional photonic crystals are etched in the light-emitting direction of the upper p-type DBR; the thermal stability and reliability of the device under high-power continuous working conditions are effectively improved, stable single-mode output is realized, the light field is enhanced, the light beam quality is improved, arraying and on-chip integration are facilitated, the problem of low efficiency of a 650nm red laser is effectively solved, the single-mode output problem of a VCSEL is solved, and the application has a good application prospect and a wide application range.

Description

Technical Field

[0001] This invention relates to the field of semiconductor lasers, and in particular to a vertical-cavity surface-emitting laser based on a composite metal substrate and a photonic crystal. Background Technology

[0002] Vertical-cavity surface-emitting lasers (VCSELs) are an important branch of semiconductor lasers. With their significant advantages such as high beam quality, low threshold current, ease of two-dimensional array integration, wafer-level testing, and low manufacturing cost, they are widely used in data centers, consumer electronics, industrial processing, and medical sensing. However, current VCSEL technology still has many shortcomings in high-power and special wavelength applications. For example, traditional gallium arsenide (GaAs)-based VCS ELs are widely used in the 850-940nm wavelength range due to their material bandgap matching advantages, but they face the problem of expanding the material system in shorter wavelength applications (such as 650nm red light). Traditional VCS ELs are usually grown on GaAs substrates, which have a low theoretical thermal conductivity at room temperature, about 55W / (m·K). When operating in high power density scenarios, the heat generated in the active region is difficult to dissipate efficiently, resulting in a sharp increase in junction temperature, which can easily lead to problems such as increased threshold current, output power saturation, and wavelength drift. In addition, in order to obtain single-mode output, the oxide confinement aperture of the VCS EL needs to be less than 3-4μm, which significantly limits the output power and has poor polarization control capability.

[0003] In view of this, how to provide a vertical cavity surface-emitting laser that can partially or completely solve the above-mentioned shortcomings is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a vertical cavity surface-emitting laser based on a composite metal substrate and a photonic crystal. By introducing multiple synergistic optimization methods at the structural and process levels, the key performance parameters of the VCSEL device are significantly improved, meeting the stringent requirements of high-performance applications for laser output quality and stability, thereby solving the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides a vertical cavity surface-emitting laser based on a composite metal substrate and photonic crystals, comprising, from bottom to top: a CIC composite metal substrate, a GaAs buffer layer, a lower n-type DBR, an n-type contact layer, a multi-junction cascaded active region, a p-type contact layer, and an upper p-type DBR; the upper p-type DBR is etched in the light-emitting direction to form multiple two-dimensional photonic crystals, and a positive electrode is disposed on the upper p-type DBR and the positive electrode is located outside the multiple two-dimensional photonic crystals;

[0006] The CIC composite metal substrate, GaAs buffer layer and lower n-type DBR form a lower rhomboid mesa, the cross-section of which is rhomboid;

[0007] The n-type contact layer, the multi-junction cascaded active region, the p-type contact layer and the upper p-type DBR form an upper rhomboid platform, and the cross-section of the upper rhomboid platform is rhomboid.

[0008] Furthermore, the CIC composite metal substrate includes an Invar alloy layer and copper layers located on the upper and lower sides of the Invar alloy layer, wherein the copper layer has a thickness of 10 μm and the Invar alloy layer has a thickness of 30 μm.

[0009] Furthermore, the thermal conductivity of the CIC composite metal substrate is 90-170 W / (m·K).

[0010] Furthermore, in the process of preparing the lower rhomboid mesa, the GaAs buffer layer is first connected to the GaAs substrate, the GaAs substrate is bonded to the temporary substrate, the GaAs substrate is peeled off by chemical treatment or heat treatment, and then the GaAs buffer layer is transferred to the CIC composite metal substrate.

[0011] Furthermore, the multi-junction cascaded active region includes:

[0012] The active region component consists of a quantum well, a first spacer layer, and an oxide confinement layer arranged sequentially from bottom to top.

[0013] A Type-II tunnel junction is disposed between adjacent active region components, and a second spacer layer is disposed between the Type-II tunnel junction and the adjacent active region components.

[0014] Furthermore, the oxidation restriction layer is subjected to wet oxidation treatment from the outer edge of the lower rhomboid platform to form asymmetric oxidation pores, the pore diameter of which is 5-8 μm and the cross-sectional shape is rhomboid.

[0015] The present invention discloses the following technical effects:

[0016] 1. Multiple two-dimensional photonic crystals are etched in the light-emitting direction of the upper p-type DBR. By introducing periodic refractive index modulation, diffraction loss is generated in the cavity mode, which makes the diffraction loss of higher-order transverse modes much greater than that of the fundamental mode. This effectively filters out higher-order modes and allows only the fundamental mode (TEM00) to resonate and output, realizing single-mode output under large aperture. This significantly enhances the single-mode stability, polarization selectivity and overall performance of the device.

[0017] 2. This invention employs a multi-junction cascaded active region, connecting multiple independent active region components in series via a Type-II tunnel junction. This allows each active region component to independently contribute optical gain, effectively improving overall optical output power, slope efficiency, and modulation bandwidth. Simultaneously, each active region component contains an independent quantum well, enabling it to emit laser light independently after current injection, superimposing optical gain and achieving efficient carrier recombination and tunneling transfer. This significantly reduces series resistance, improves injection efficiency, effectively reduces thermal load, and enhances high-power continuous operation capability.

[0018] 3. Asymmetric oxide holes are formed by wet oxidation of the oxide confinement layer from the outer edge of the lower rhombic mesa. The diameter of the oxide holes is 5-8 μm, and the cross-sectional shape is rhombic. This overcomes the isotropy of circular oxide holes, increases mode selectivity and polarization selectivity, and ensures the polarization stability of the output light. These rhombic oxide holes not only confine the current injection region and guide the light field, but their asymmetry also further enhances polarization control capabilities. This structure works synergistically with the two-dimensional photonic crystal to jointly achieve mode control and polarization selection.

[0019] 4. The entire VCSEL is set on a CIC composite metal substrate. Since Invar alloy has a very low coefficient of thermal expansion, it can ensure stress matching of the VCSEL epitaxial layer during thermal expansion, avoid structural cracks caused by thermal mismatch, and significantly improve the heat dissipation capacity of the VCSEL, enabling the device to operate stably under higher injection current and extend its service life. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of the present invention;

[0022] Figure 2 This is a top view of the structure;

[0023] Figure 3 Schematic diagram of a multi-junction cascaded active region;

[0024] Among them, 100 is a CIC composite metal substrate; 200 is a GaAs buffer layer; 300 is a lower n-type DBR; 400 is an n-type contact layer; 500 is a multi-junction cascaded active region; 501 is a quantum well; 502 is a first spacer layer; 503 is an oxide confinement layer; 504 is a Type-II tunnel junction; 600 is a p-type contact layer; 700 is an upper p-type DBR; 701 is a two-dimensional photonic crystal; and 800 is a positive electrode. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] This invention provides a vertical-cavity surface-emitting laser based on a composite metal substrate and photonic crystals, comprising, from bottom to top: a CIC composite metal substrate 100, a GaAs buffer layer 200, a lower n-type DBR 300, an n-type contact layer 400, a multi-junction cascaded active region 500, a p-type contact layer 600, and an upper p-type DBR 700; the upper p-type DBR 700 is etched in the light-emitting direction to form multiple two-dimensional photonic crystals 701, and a positive electrode 800 is disposed on the upper p-type DBR 700 and is located outside the multiple two-dimensional photonic crystals 701;

[0028] The CIC composite metal substrate 100, GaAs buffer layer 200 and lower n-type DBR 300 form a lower rhomboid mesa, and the cross-section of the lower rhomboid mesa is rhomboid.

[0029] The upper rhomboid platform is composed of an n-type contact layer 400, a multi-junction cascaded active region 500, a p-type contact layer 600, and an upper p-type DBR 700. The cross-section of the upper rhomboid platform is rhomboid.

[0030] In this embodiment, the cross-sectional dimensions of each structure in the upper rhomboid platform are consistent, and the cross-sectional dimensions of each structure in the lower rhomboid platform are consistent, which can further improve the polarization stability of the device.

[0031] In this embodiment, the CIC composite metal substrate 100 includes an Invar alloy layer and copper layers located on the upper and lower sides of the Invar alloy layer. The copper layer has a thickness of 10 μm, and the Invar alloy layer has a thickness of 30 μm.

[0032] In this embodiment, the thermal conductivity of the CIC composite metal substrate 100 is 90-170 W / (m·K).

[0033] In this embodiment, during the preparation of the lower rhomboid mesa, the GaAs buffer layer 200 is first connected to the GaAs substrate, the GaAs substrate is bonded to the temporary substrate, the GaAs substrate is peeled off by chemical or thermal treatment, and then the GaAs buffer layer 200 is transferred to the CIC composite metal substrate 100.

[0034] In this embodiment, the multi-junction cascaded active region 500 includes:

[0035] The active region component is composed of a quantum well 501, a first spacer layer 502 and an oxide confinement layer 503 arranged from bottom to top;

[0036] A Type-II tunnel junction 504 is disposed between adjacent active area components, and a second spacer layer is disposed between the Type-II tunnel junction 504 and the adjacent active area components.

[0037] In the multi-junction cascaded active region 500, multiple active region components with independent quantum wells 501 are vertically connected in series via highly doped Type-II tunnel junctions 504. Each active region component can generate laser radiation after carrier injection, achieving cascaded superposition of gain responses and effectively improving the overall output power and gain efficiency of the device. The tunnel junction structure provides an efficient carrier recombination channel and tunneling migration mechanism, thereby maintaining excellent electrical injection efficiency without increasing series impedance. In addition, the multi-junction structure achieves spatially uniform distribution of current and heat, significantly mitigating the thermal focusing effect and improving the thermal stability and reliability of the device under high-power continuous operation conditions.

[0038] In this embodiment, the oxide confinement layer 503 is wet-oxidized from the outer edge of the lower rhombic mesa to form asymmetric oxide holes. The diameter of the oxide holes is 5-8 μm, and the cross-sectional shape is rhombic. The two-dimensional photonic crystal 701 works together with the rhombic oxide holes to improve the single-mode capability and selective polarization of the device.

[0039] Through experimentation, this embodiment demonstrates that even with an oxide hole diameter of 5-8 μm, a single-mode 650 nm laser with high polarization can still be obtained, effectively solving the problem of low efficiency in 650 nm red lasers and the challenge of single-mode output in VCSELs.

[0040] Regarding heat dissipation, this embodiment enables the VCSEL to achieve greater output power than traditional VCSELs even when operating at a lower injection current. The reduced operating current effectively suppresses Joule heating inside the VCSEL, mitigating the temperature rise effect that is detrimental to VCSEL performance.

[0041] Based on the simulation of room temperature (300K) working environment using PICS3D software, the test subjects were a traditional VCSEL (single junction) and this embodiment. The results showed that the highest temperature occurred in the active region, which was mainly due to Joule heating caused by leakage current and non-radiative recombination heat. Under the same output power (e.g., 10 milliwatts), the highest temperature in the active region of the traditional VCSEL was 358K, while the highest operating temperature in the active region of this embodiment was 327K, and the temperature rise was significantly suppressed.

[0042] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0043] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A vertical-cavity surface-emitting laser based on a composite metal substrate and a photonic crystal, characterized in that, The structure comprises, from bottom to top, a CIC composite metal substrate (100), a GaAs buffer layer (200), a lower n-type DBR (300), an n-type contact layer (400), a multi-junction cascaded active region (500), a p-type contact layer (600), and an upper p-type DBR (700). The upper p-type DBR (700) is etched in the light-emitting direction to form multiple two-dimensional photonic crystals (701). A positive electrode (800) is disposed on the upper p-type DBR (700), and the positive electrode (800) is located outside the multiple two-dimensional photonic crystals (701). The CIC composite metal substrate (100), GaAs buffer layer (200) and lower n-type DBR (300) form a lower rhomboid mesa, the cross-section of which is rhomboid. The n-type contact layer (400), the multi-junction cascaded active region (500), the p-type contact layer (600) and the upper p-type DBR (700) form an upper rhomboid platform, the cross-section of which is rhomboid. The multi-junction cascaded active region (500) includes: The active region component is composed of a quantum well (501), a first spacer layer (502), and an oxide confinement layer (503) arranged sequentially from bottom to top; A Type-II tunnel junction (504) is disposed between adjacent active region components, and a second spacer layer is disposed between the Type-II tunnel junction (504) and the adjacent active region components. The oxide confinement layer (503) is subjected to wet oxidation treatment from the outer edge of the lower rhomboid platform to form asymmetric oxide pores, the pore diameter of which is 5-8 μm and the cross-sectional shape is rhomboid.

2. A vertical-cavity surface-emitting laser based on a composite metal substrate and a photonic crystal according to claim 1, characterized in that, The CIC composite metal substrate (100) includes an Invar alloy layer and copper layers located on the upper and lower sides of the Invar alloy layer, the copper layer having a thickness of 10 μm and the Invar alloy layer having a thickness of 30 μm.

3. A vertical-cavity surface-emitting laser based on a composite metal substrate and a photonic crystal according to claim 2, characterized in that, The thermal conductivity of the CIC composite metal substrate (100) is 90-170 W / (m·K).

4. A vertical-cavity surface-emitting laser based on a composite metal substrate and a photonic crystal according to claim 1, characterized in that, In the process of preparing the lower rhomboid mesa, the GaAs buffer layer (200) is first connected to the GaAs substrate, the GaAs substrate is bonded to the temporary substrate, the GaAs substrate is peeled off by chemical treatment or heat treatment, and then the GaAs buffer layer (200) is transferred to the CIC composite metal substrate (100).

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