High-power low-divergence-angle multi-junction cascade vertical cavity surface laser structure and preparation method thereof

Abstract

The invention relates to the technical field of semiconductor lasers. Along with the increase of the junction number of the vertical cavity surface emitting laser, the cavity length, the number of oxidation limiting layers and the heat are correspondingly increased, so that a larger divergence angle and the reduction of power are caused; according to the high-power low-divergence-angle multi-junction cascade vertical cavity surface laser structure and the preparation method thereof, the divergence angle is reduced by reducing the number of oxidation limiting layers and the interval between two active areas, the active areas are connected in series in the same resonant cavity through tunnel junctions, and the laser structure is high in power and low in divergence angle. According to the vertical cavity surface emitting laser, the resistance and the absorption loss are not multiplied, the output power and the electro-optical conversion efficiency of the vertical cavity surface emitting laser are remarkably improved, the GaAs tunnel junction is inserted into the top DBR, and the p-DBR is converted into the n-DBR, so that the Joule heat is reduced, and the power and the power conversion efficiency are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor lasers, and more particularly to a high-power, low-divergence-angle multi-junction cascade vertical cavity surface laser structure and a preparation method thereof. Background Art

[0002] Vertical cavity surface emitting lasers have many advantages such as small size, low threshold current, easy to realize two-dimensional planar and optoelectronic integration, single longitudinal film operation, and high power output. They have been increasingly widely used in optical interconnection, lidar, 3D sensing, intelligent manufacturing, medical diagnosis, consumer electronics and other fields. Traditional single-junction vertical cavity surface emitting lasers have low output power due to their small gain area and cannot meet the needs of these applications. Compared with traditional single-junction vertical cavity surface emitting lasers, multi-junction cascaded vertical cavity surface emitting lasers use highly doped tunnel junctions to connect multiple active regions in series, thereby effectively increasing the gain volume. Without increasing the light output aperture, multi-junction cascaded vertical cavity surface emitting lasers can achieve a multiple increase in power compared to single-junction vertical cavity surface emitting lasers with the same aperture, and significantly improve the power conversion efficiency of the device.

[0003] As the number of junctions in a VCSEL increases, the cavity length, the number of oxide confinement layers, and the amount of heat generated also increase accordingly, resulting in a larger divergence angle and reduced power. A larger divergence angle can adversely affect the resolution and distance measurement accuracy of lidar, as well as fiber coupling. Therefore, when designing a multi-junction cascade VCSEL, a method is needed that can reduce the cavity length, the number of oxide confinement layers, and the amount of heat generated. Summary of the Invention

[0004] To address the problems of large divergence angle and increased heat generation faced by current 940nm oxide-confined vertical-cavity surface-emitting lasers, the present invention aims to provide a high-power, low-divergence-angle multi-junction cascaded vertical-cavity surface-emitting laser structure and preparation method. By reducing the number of oxide confinement layers and the spacing between the two active regions, the divergence angle is reduced. The structure of the present invention utilizes tunnel junctions to connect the active regions in series within the same resonant cavity. This significantly improves the output power and electro-optical conversion efficiency of the vertical-cavity surface-emitting laser without doubling the resistance and absorption losses.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A high-power, low-divergence multi-junction cascade vertical cavity surface emitting laser structure comprises an n-GaAs substrate and an n-GaAs buffer layer, an n-distributed Bragg reflector, an n-Al 0.6-0.3 Ga 0.4-0.7 As space layer, gain region, p-Al 0.3-0.6Ga 0.7-0.4 As space layer, p-distributed Bragg reflector, Al 0.98 Ga 0.02 As oxide confinement layer, p-distributed Bragg reflector, GaAs tunnel junction layer, n-distributed Bragg reflector and p-GaAs cap layer, wherein:

[0007] The n-GaAs buffer layer is grown on the n-GaAs substrate, the n-distributed Bragg reflector is grown on the n-GaAs buffer layer, and the n-Al 0.6-0.3 Ga 0.4-0.7 The As spacer layer is grown on the n-distributed Bragg reflector, and the gain region is grown on the n-Al 0.6- 0.3 Ga 0.4-0.7 As space layer grows, p-Al 0.3-0.6 Ga 0.7-0.4 As spacer layer is grown on the gain region, and p-distributed Bragg reflector is grown on p-Al 0.3-0.6 Ga 0.7-0.4 As space layer grows, Al 0.98 Ga 0.02 As oxide confinement layer is grown on the p-distributed Bragg reflector, which is grown on the Al 0.98 Ga 0.02 As oxide confinement layer, a GaAs tunnel junction layer is grown on the p-distributed Bragg reflector, an n-distributed Bragg reflector is grown on the GaAs tunnel junction layer, and a p-GaAs cap layer is grown on the n-distributed Bragg reflector.

[0008] Furthermore, the thickness of the n-GaAs substrate is 250 nm and the doping concentration is 3×10 18 cm -1 ; The thickness of the n-GaAs buffer layer is 500nm and the doping concentration is 2×10 18 cm -1 The p-GaAs cap layer has a thickness of 5 nm and a doping concentration of 1.5×10 18 cm -1 The GaAs tunnel junction layer includes a p-GaAs tunnel junction layer and an n-GaAs tunnel junction layer. The p-GaAs tunnel junction layer has a thickness of 5 nm and a doping concentration of 8×10 25 cm -1 ; The thickness of the n-GaAs tunnel junction layer is 15nm and the doping concentration is 3×10 25 cm -1 .

[0009] Furthermore, the gain region includes four active regions, and Al is set between adjacent active regions. 0.6 Ga 0.4As space layer, GaAs tunnel junction layer, Al 0.6 Ga 0.4 As space layer, Al is added between the two active regions in the middle of the gain region 0.6 Ga 0.4 As space layer and Al 0.98 Ga 0.02 As oxide limiting layer, Al 0.6 Ga 0.4 As space layer, Al 0.98 Ga 0.02 As oxidation restriction layer, Al 0.6 Ga 0.4 As space layer, GaAs tunnel junction layer, Al 0.6 Ga 0.4 As space layer, and the GaAs tunnel junction layer has the same structure as the GaAs tunnel junction layer grown on the p-distributed Bragg reflector.

[0010] Furthermore, the active region comprises four layers of GaAs 0.92 P 0.08 Barrier layer, three layers of In 0.16 Ga 0.84 As quantum well, GaAs 0.92 P 0.08 The barrier layer thickness is 6.2nm, In 0.16 Ga 0.84 The thickness of the As quantum well is 4.5 nm.

[0011] Furthermore, the three Al 0.6 Ga 0.4 The thickness of the As space layer is 37.8nm, 121.5nm, and 40.7nm respectively. The Al 0.6 Ga 0.4 The thickness of the As spacer layer is 42 nm.

[0012] Furthermore, the n-distributed Bragg reflector near the crystal plane includes 35.5 pairs of n-GaAs high refractive index layers and n-Al 0.9 Ga 0.1 As low refractive index layer, starting from high to low Al x Ga 1-x As composition graded layer; the n-distributed Bragg reflector away from the crystal plane includes 16.5 pairs of n-GaAs high refractive index layers and n-Al 0.9 Ga 0.1 As low refractive index layer, the starting end is n-GaAs high refractive index layer; Al inserted between the two layers of different refractive index x Ga 1-xAs composition gradient layer, n-GaAs high refractive index layer thickness is 47.6nm, doping concentration is 2×10 18 cm -1 ;Al 0.9 Ga 0.1 The As low refractive index layer has a thickness of 55.7 nm and a doping concentration of 2×10 18 cm -1 ;Al x Ga 1-x The thickness of the As composition graded layer is 20 nm, and the doping concentration is 2.5×10 18 cm -1 , wherein the Al concentration x gradually changes from the high refractive index layer to the low refractive index layer in the range of 0 to 0.9, and from the low refractive index layer to the high refractive index layer in the range of 0.9 to 0; the n-distributed Bragg reflector is n-type doped;

[0013] In p-Al 0.3-0.6 Ga 0.7-0.4 The p-distributed Bragg reflector grown on the As spacer is a p-Al 0.9 Ga 0.1 As low refractive index layer, doping concentration is 2×10 18 cm -1 , thickness is 62.7nm; in Al 0.98 Ga 0.02 The p-distributed Bragg reflector grown on the As oxide confinement layer is a 20nm thick Al x Ga 1-x As composition gradient layer, p-GaAs high refractive index layer with a thickness of 16.59nm, Al layer with a thickness of 20nm from high to low x Ga 1-x As composition graded layer, p-Al with a thickness of 44.04nm 0.9 Ga 0.1 As low refractive index layer and Al with thickness of 20nm from low to high x Ga 1-x As composition graded layer; p-type doping in p-distributed Bragg reflector.

[0014] Furthermore, n-Al 0.6-0.3 Ga 0.4-0.7 The thickness of the As space layer is 123nm; the p-Al 0.3-0.6 Ga 0.7-0.4 The thickness of the As space layer is 123 nm; the Al 0.98 Ga 0.02 The thickness of the As oxide restriction layer is 30 nm.

[0015] A method for preparing a high-power, low-divergence-angle multi-junction cascade vertical-cavity surface-emitting laser is provided, which is used to prepare the high-power, low-divergence-angle multi-junction cascade vertical-cavity surface-emitting laser structure described above, and is characterized in that it specifically comprises the following steps:

[0016] Step 1. Cleaning the n-GaAs substrate surface: introducing hydrogen gas at a reaction chamber temperature of 700-740°C for 5-15 minutes to clean away particle contaminants and remove surface oxygen atoms.

[0017] Step 2. n-GaAs buffer layer growth: the temperature is reduced to 650-680°C, the trimethyl gallium flow rate is 90 sccm, the arsine flow rate is 440 sccm, the silane flow rate is 50-100 sccm, the growth thickness is 500 nm, and the n-type doping concentration is 2×10 18 cm -3 ;

[0018] Step 3. n-Distributed Bragg Reflector Growth: Growth temperature is 650-680℃, DBR laser structure is grown, a total of 35.5 cycles; a DBR laser growth cycle is: from high to low Al x Ga 1-x As composition gradient layer, Al 0.9 Ga 0.1 As low refractive index layer, Al from low to high x Ga 1-x As composition graded layer and n-GaAs high refractive index layer;

[0019] Step 4.Al 0.3-0.6 Ga 0.7-0.4 As space layer growth: the temperature remains unchanged, the trimethylgallium flow rate is 55 sccm, the trimethylaluminum flow rate is 125 sccm, the arsine flow rate is 440 sccm, and the growth thickness is 123 nm;

[0020] Step 5. Active Area Growth: Step 5.1GaAs 0.92 P 0.08 Barrier layer: The reaction chamber temperature remains unchanged, the trimethylgallium flow rate is 45 sccm, the arsine flow rate is 800-1500 sccm, and the phosphine flow rate is 300-500 sccm; Step 5.2In 0.16 Ga 0.84 As quantum well layer: temperature raised to 680-700°C, trimethylgallium flow rate of 64 sccm, trimethylindium flow rate of 50 sccm, arsine flow rate of 1000-2000 sccm; repeat steps 5.1-5.2 three times;

[0021] Step 6.Al 0.6 Ga 0.4As space layer growth: the same growth process as step 4, the growth thickness is 42nm;

[0022] Step 7. GaAs tunnel junction layer growth: p-GaAs tunnel junction layer growth: temperature dropped to 550-650°C, trimethyl gallium flow rate was 97 sccm, trimethyl aluminum flow rate was 28 sccm, arsine flow rate was 1160 sccm, carbon tetrabromide flow rate was 10-25 sccm, growth thickness was 5 nm, p-type doping concentration was 8×10 19 cm -3 n-GaAs tunnel junction layer growth: growth temperature 550-650°C, trimethylgallium flow rate 97 sccm, trimethylaluminum flow rate 28 sccm, arsine flow rate 1160 sccm, carbon tetrabromide flow rate 10-25 sccm, growth thickness 20 nm, p-type doping concentration 3×10 19 cm -3 ;

[0023] Step 8.Al 0.6 Ga 0.4 As spatial layer growth: same as step 6;

[0024] Active area growth: same as step 5;

[0025] Al 0.6 Ga 0.4 As space layer growth: same as step 4, the growth thickness is 37.8nm;

[0026] Step 9.Al 0.98 Ga 0.02 As oxide confinement layer growth: growth temperature 650-680°C, trimethylgallium flow rate 55 sccm, trimethylaluminum flow rate 125 sccm, arsine flow rate 440 sccm, carbon tetrabromide flow rate 10-25 sccm, growth thickness 30 nm, p-doping concentration 2×10 17 cm -3 ;

[0027] Step 10.Al 0.6 Ga 0.4 As space layer growth: same as step 4, growth thickness is 121.5nm;

[0028] GaAs tunnel junction layer growth: same as step 7;

[0029] Al 0.6 Ga 0.4 As space layer growth: same as step 4, the growth thickness is 40.7nm;

[0030] Active area growth: same as step 5;

[0031] Al 0.6 Ga 0.4 As spatial layer growth: same as step 6;

[0032] GaAs tunnel junction layer growth: same as step 7;

[0033] Al 0.6 Ga 0.4 As spatial layer growth: same as step 6;

[0034] Active area growth: same as step 5;

[0035] Al 0.3-0.6 Ga 0.7-0.4 As space layer growth: same as step 4, growth thickness is 123nm;

[0036] Step 11. p-distributed Bragg reflector growth: same as Al in step 3 0.9 Ga 0.1 The As low refractive index layer is grown using the same process, with a thickness of 62.7 nm.

[0037] Al 0.98 Ga 0.02 As oxide confinement layer growth: same as step 9;

[0038] p-distributed Bragg reflector growth: same as step 3 growth process, from low to high Al x Ga 1-x The thickness of the As composition gradient layer is 20nm, the thickness of the p-GaAs high refractive index layer is 16.59nm, and the Al x Ga 1-x The thickness of the As composition gradient layer is 20nm, and the p-Al 0.9 Ga 0.1 The thickness of the As low refractive index layer is 44.04nm, and the thickness of the Al x Ga 1-x The thickness of the As composition gradient layer is 20 nm;

[0039] GaAs tunnel junction layer growth: same as step 7;

[0040] n-Distributed Bragg reflector growth: The growth temperature is 650-680℃, and the DBR laser structure is grown for a total of 16.5 cycles. A DBR laser growth cycle is: n-GaAs high refractive index layer, Al x Ga 1-x As composition gradient layer, Al 0.9 Ga 0.1 As low refractive index layer, Al from low to high x Ga1-x As component gradient layer;

[0041] Step 12. p-GaAs cap layer growth: temperature dropped to 550-650°C, trimethylgallium flow rate was 90 sccm, arsine flow rate was 440 sccm, carbon tetrabromide flow rate was 10-25 sccm, growth thickness was 5 nm, and p-type doping concentration was greater than 1×10 19 cm -3 .

[0042] Furthermore, the growth process of the DBR laser structure is as follows:

[0043] From high to low Al x Ga 1-x As composition gradient layer growth: x linearly changes from 0 to 0.9, and the doping concentration is 2.5×10 18 cm -3 , thickness is 20nm;

[0044] Al 0.9 Ga 0.1 As low refractive index layer growth: doping concentration is 2×10 18 cm -3 , thickness is 55.7nm;

[0045] From low to high Al x Ga 1-x As composition gradient layer growth: x linearly changes from 0.9 to 0, and the doping concentration is 2.5×10 18 cm -3 , thickness is 20nm;

[0046] Growth of GaAs high refractive index layer: doping concentration is 2×10 18 cm -3 , thickness is 47.6nm;

[0047] In the above steps, the doping concentration is controlled by adjusting the SiH4 flow rate; n-type doping is used in the n-distributed Bragg reflector, and p-type doping is used in the p-distributed Bragg reflector.

[0048] In summary, the invention has the following beneficial effects:

[0049] The junction-cascaded vertical cavity surface-emitting laser (VCSEL) of the present invention reduces the cavity length and the number of oxidized confinement layers, thus reducing the divergence angle. It utilizes a tunnel junction to connect the active regions in series within the same resonant cavity, significantly improving the laser's output power and electro-optical conversion efficiency without exponentially increasing resistance and absorption losses. A GaAs tunnel junction is inserted into the top DBR, converting the p-DBR into an n-DBR, thereby reducing Joule heating and improving power and power conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Schematic diagram of a multi-junction cascade vertical cavity surface emitting laser according to the present invention;

[0051] Figure 2 Schematic diagram of the energy band of the four-junction cascade active region;

[0052] Figure 3 This is the PVI curve of the four-junction cascade vertical cavity surface emitting laser under room temperature continuous conditions;

[0053] Figure 4 This is the PCE-I curve of the four-junction cascade vertical cavity surface emitting laser under continuous conditions at room temperature;

[0054] Figure 5 is the far-field divergence angle of the four-junction cascaded vertical cavity surface emitting laser. DETAILED DESCRIPTION

[0055] The present invention will be described in further detail below with reference to the accompanying drawings.

[0056] It should be noted that, for the sake of convenience, the directions described below are consistent with the directions of the drawings themselves, but do not limit the structure of the present invention.

[0057] like Figures 1 to 5 As shown, the present invention provides a high-power, low-divergence multi-junction cascade vertical cavity surface emitting laser structure, which belongs to the structure of high-power, low-divergence multi-junction cascade vertical cavity surface emitting laser, and can solve the problems of large divergence angle, free carrier light loss, and severe Joule heat. The divergence angle is reduced by reducing the cavity length and the number of oxidized confinement layers. In addition, a GaAs tunnel junction is inserted into the top DBR to convert the p-DBR into an n-DBR, thereby reducing Joule heat and improving power and power conversion efficiency. The structure comprises an n-GaAs substrate and an n-GaAs buffer layer, an n-distributed Bragg reflector, and an n-Al2O3 mirror arranged in sequence along the growth direction. 0.6-0.3 Ga 0.4-0.7 As space layer, gain region, p-Al 0.3-0.6 Ga 0.7-0.4 As space layer, p-distributed Bragg reflector, Al 0.98 Ga 0.02 As oxide confinement layer, p-distributed Bragg reflector, GaAs tunnel junction layer, n-distributed Bragg reflector and p-GaAs cap layer, wherein:

[0058] The n-GaAs buffer layer is grown on the n-GaAs substrate, the n-distributed Bragg reflector is grown on the n-GaAs buffer layer, and the n-Al 0.6-0.3 Ga 0.4-0.7As spacer layer is grown on n-distributed Bragg reflector, n-Al 0.6-0.3 Ga 0.4-0.7 The thickness of the As space layer is 123nm; the gain region is in the n-Al 0.6-0.3 Ga 0.4-0.7 As space layer grows, p-Al 0.3-0.6 Ga 0.7-0.4 As spacer layer is grown on the gain region, and p-distributed Bragg reflector is grown on p-Al 0.3-0.6 Ga 0.7-0.4 As space layer grows, p-Al 0.3- 0.6 Ga 0.7-0.4 The thickness of the As space layer is 123nm; the Al 0.98 Ga 0.02 As oxide confinement layer is grown on the p-distributed Bragg reflector, Al 0.98 Ga 0.02 The thickness of the As oxide confinement layer is 30 nm; the p-distributed Bragg reflector is on the Al 0.98 Ga 0.02 As oxide confinement layer. A GaAs tunnel junction layer is grown on the p-distributed Bragg reflector, an n-distributed Bragg reflector is grown on the GaAs tunnel junction layer, and a p-GaAs cap layer is grown on the n-distributed Bragg reflector.

[0059] The thickness of the n-GaAs substrate is 250 nm and the doping concentration is 3×10 18 cm -1 ; The thickness of the n-GaAs buffer layer is 500nm and the doping concentration is 2×10 18 cm -1 The p-GaAs cap layer has a thickness of 5 nm and a doping concentration of 1.5×10 18 cm -1 The GaAs tunnel junction layer includes a p-GaAs tunnel junction layer and an n-GaAs tunnel junction layer, the p-GaAs tunnel junction layer has a thickness of 5nm and a doping concentration of 8×10 25 cm -1 ; The thickness of the n-GaAs tunnel junction layer is 15nm and the doping concentration is 3×10 25 cm -1 .

[0060] The gain region consists of four active regions, with Al2O3 layers placed between adjacent active regions. 0.6 Ga 0.4 As space layer, GaAs tunnel junction layer, Al 0.6 Ga 0.4 As space layer, Al is added between the two active regions in the middle of the gain region 0.6 Ga0.4 As space layer and Al 0.98 Ga 0.02 As oxide limiting layer, Al 0.6 Ga 0.4 As space layer, Al 0.98 Ga 0.02 As oxidation restriction layer, Al 0.6 Ga 0.4 As space layer, GaAs tunnel junction layer, Al 0.6 Ga 0.4 As space layer, and the GaAs tunnel junction layer has the same structure as the GaAs tunnel junction layer grown on the p-distributed Bragg reflector. The three Al 0.6 Ga 0.4 The thickness of the As space layer is 37.8nm, 121.5nm, and 40.7nm respectively. The Al 0.6 Ga 0.4 The thickness of the As spacer layer is 42 nm.

[0061] The active region consists of four layers of GaAs 0.92 P 0.08 Barrier layer, three layers of In 0.16 Ga 0.84 As quantum well, GaAs 0.92 P 0.08 The barrier layer thickness is 6.2nm, In 0.16 Ga 0.84 The thickness of the As quantum well is 4.5 nm.

[0062] The n-distributed Bragg reflector near the crystal plane consists of 35.5 pairs of n-GaAs high refractive index layers and n-Al 0.9 Ga 0.1 As low refractive index layer, starting from high to low Al x Ga 1-x As composition graded layer, the n-distributed Bragg reflector away from the crystal plane includes 16.5 pairs of n-GaAs high refractive index layers and n-Al 0.9 Ga 0.1 As low refractive index layer, the starting end is n-GaAs high refractive index layer; Al inserted between the two layers of different refractive index x Ga 1-x The As composition gradient layer and the GaAs high refractive index layer have a thickness of 47.6 nm and a doping concentration of 2×10 18 cm -1 ;Al 0.9 Ga 0.1 The As low refractive index layer has a thickness of 55.7 nm and a doping concentration of 2×1018 cm -1 ;Al x Ga 1-x The thickness of the As composition graded layer is 20 nm, and the doping concentration is 2.5×10 18 cm -1 , where the Al concentration x gradually changes from 0 to 0.9 from the high refractive index layer to the low refractive index layer, and gradually changes from 0.9 to 0 from the low refractive index layer to the high refractive index layer; the n-distributed Bragg reflector is n-type doped.

[0063] In p-Al 0.3-0.6 Ga 0.7-0.4 The p-distributed Bragg reflector grown on the As spacer is a p-Al 0.9 Ga 0.1 As low refractive index layer, doping concentration is 2×10 18 cm -1 , thickness is 62.7nm; in Al 0.98 Ga 0.02 The p-distributed Bragg reflector grown on the As oxide confinement layer is a 20nm thick Al x Ga 1-x As composition gradient layer, p-GaAs high refractive index layer with a thickness of 16.59nm, Al layer with a thickness of 20nm from high to low x Ga 1-x As composition graded layer, p-Al with a thickness of 44.04nm 0.9 Ga 0.1 As low refractive index layer and Al with thickness of 20nm from low to high x Ga 1-x As composition graded layer; p-type doping in p-distributed Bragg reflector.

[0064] Insert Al x Ga 1-x The As composition gradient layer is designed to avoid the higher voltage drop and series resistance caused by the sudden change of refractive index, reduce the impact of thermal effects on device performance, and appropriately increase the doping concentration in the gradient area to achieve the purpose of significantly reducing the potential barrier while ensuring a higher reflectivity.

[0065] The present invention also discloses a method for preparing a high-power, low-divergence-angle multi-junction cascade vertical-cavity surface-emitting laser, which is used to prepare the above-mentioned high-power, low-divergence-angle multi-junction cascade vertical-cavity surface-emitting laser structure, and specifically comprises the following steps:

[0066] Step 1. Cleaning the n-GaAs substrate surface: introducing hydrogen gas at a reaction chamber temperature of 700-740°C for 5-15 minutes to clean away particle contaminants and remove surface oxygen atoms.

[0067] Step 2. n-GaAs buffer layer growth: the temperature is reduced to 650-680°C, the trimethyl gallium flow rate is 90 sccm, the arsine flow rate is 440 sccm, the silane flow rate is 50-100 sccm, the growth thickness is 500 nm, and the n-type doping concentration is 2×10 18 cm -3 ;

[0068] Step 3. n-Distributed Bragg reflector growth: Growth temperature is 650-680℃, grow DBR laser structure, a total of 35.5 cycles; a DBR laser growth cycle is: from high to low Al x Ga 1-x As composition gradient layer, Al 0.9 Ga 0.1 As low refractive index layer, Al from low to high x Ga 1-x As composition graded layer and n-GaAs high refractive index layer;

[0069] Step 4.Al 0.3-0.6 Ga 0.7-0.4 As space layer growth: the temperature remains unchanged, the trimethylgallium flow rate is 55 sccm, the trimethylaluminum flow rate is 125 sccm, the arsine flow rate is 440 sccm, and the growth thickness is 123 nm;

[0070] Step 5. Active Area Growth: Step 5.1GaAs 0.92 P 0.08 Barrier layer: The reaction chamber temperature remains unchanged, the trimethylgallium flow rate is 45 sccm, the arsine flow rate is 800-1500 sccm, and the phosphine flow rate is 300-500 sccm; Step 5.2In 0.16 Ga 0.84 As quantum well layer: temperature raised to 680-700°C, trimethylgallium flow rate of 64 sccm, trimethylindium flow rate of 50 sccm, arsine flow rate of 1000-2000 sccm; repeat steps 5.1-5.2 three times;

[0071] Step 6.Al 0.6 Ga 0.4 As space layer growth: the same growth process as step 4, the growth thickness is 42nm;

[0072] Step 7. GaAs tunnel junction layer growth: p-GaAs tunnel junction layer growth: temperature dropped to 550-650°C, trimethyl gallium flow rate was 97 sccm, trimethyl aluminum flow rate was 28 sccm, arsine flow rate was 1160 sccm, carbon tetrabromide flow rate was 10-25 sccm, growth thickness was 5 nm, p-type doping concentration was 8×10 19 cm -3n-GaAs tunnel junction layer growth: growth temperature 550-650°C, trimethylgallium flow rate 97 sccm, trimethylaluminum flow rate 28 sccm, arsine flow rate 1160 sccm, carbon tetrabromide flow rate 10-25 sccm, growth thickness 20 nm, p-type doping concentration 3×10 19 cm -3 ;

[0073] Step 8.Al 0.6 Ga 0.4 As spatial layer growth: same as step 6;

[0074] Active area growth: same as step 5;

[0075] Al 0.6 Ga 0.4 As space layer growth: same as step 4, the growth thickness is 37.8nm;

[0076] Step 9.Al 0.98 Ga 0.02 As oxide confinement layer growth: growth temperature 650-680°C, trimethylgallium flow rate 55 sccm, trimethylaluminum flow rate 125 sccm, arsine flow rate 440 sccm, carbon tetrabromide flow rate 10-25 sccm, growth thickness 30 nm, p-doping concentration 2×10 17 cm -3 ;

[0077] Step 10.Al 0.6 Ga 0.4 As space layer growth: same as step 4, growth thickness is 121.5nm;

[0078] GaAs tunnel junction layer growth: same as step 7;

[0079] Al 0.6 Ga 0.4 As space layer growth: same as step 4, the growth thickness is 40.7nm;

[0080] Active area growth: same as step 5;

[0081] Al 0.6 Ga 0.4 As spatial layer growth: same as step 6;

[0082] GaAs tunnel junction layer growth: same as step 7;

[0083] Al 0.6 Ga 0.4 As spatial layer growth: same as step 6;

[0084] Active area growth: same as step 5;

[0085] Al 0.3-0.6 Ga 0.7-0.4 As space layer growth: same as step 4, growth thickness is 123nm;

[0086] Step 11. p-distributed Bragg reflector growth: same as Al in step 3 0.9 Ga 0.1 The As low refractive index layer is grown using the same process, with a thickness of 62.7 nm.

[0087] Al 0.98 Ga 0.02 As oxide confinement layer growth: same as step 9;

[0088] p-distributed Bragg reflector growth: same as step 3 growth process, from low to high Al x Ga 1-x The thickness of the As composition gradient layer is 20nm, the thickness of the p-GaAs high refractive index layer is 16.59nm, and the Al x Ga 1-x The thickness of the As composition gradient layer is 20nm, and the p-Al 0.9 Ga 0.1 The thickness of the As low refractive index layer is 44.04nm, and the thickness of the Al x Ga 1-x The thickness of the As composition gradient layer is 20 nm;

[0089] GaAs tunnel junction layer growth: same as step 7;

[0090] n-Distributed Bragg reflector growth: The growth temperature is 650-680℃, and the DBR laser structure is grown for a total of 16.5 cycles. A DBR laser growth cycle is: n-GaAs high refractive index layer, Al x Ga 1-x As composition gradient layer, Al 0.9 Ga 0.1 As low refractive index layer, Al from low to high x Ga 1-x As component gradient layer;

[0091] Step 12. p-GaAs cap layer growth: temperature dropped to 550-650°C, trimethylgallium flow rate was 90 sccm, arsine flow rate was 440 sccm, carbon tetrabromide flow rate was 10-25 sccm, growth thickness was 5 nm, and p-type doping concentration was greater than 1×10 19 cm -3 .

[0092] The growth process of the DBR laser structure is as follows:

[0093] From high to low Al x Ga 1-x As composition gradient layer growth: x linearly changes from 0 to 0.9, and the doping concentration is 2.5×10 18 cm -3 , thickness is 20nm;

[0094] Al 0.9 Ga 0.1 As low refractive index layer growth: doping concentration is 2×10 18 cm -3 , thickness is 55.7nm;

[0095] From low to high Al x Ga 1-x As composition gradient layer growth: x linearly changes from 0.9 to 0, and the doping concentration is 2.5×10 18 cm -3 , thickness is 20nm;

[0096] Growth of GaAs high refractive index layer: doping concentration is 2×10 18 cm -3 , thickness is 47.6nm;

[0097] In the above steps, the doping concentration is controlled by adjusting the SiH4 flow rate; n-type doping is used in the n-distributed Bragg reflector, and p-type doping is used in the p-distributed Bragg reflector.

[0098] like Figure 1 The vertical cavity surface emitting laser structure with multi-junction cascade is shown. Figure 2 Schematic diagram of the band structure of a multi-junction cascade active region. Injected electrons radiatively recombine to generate a photon, which then jumps from the conduction band to the valence band. When the tunnel junction is reversed, the recombined electrons, under the influence of the electric field, tunnel to the conduction band of the next active region, where they undergo further radiative recombination. When an electron traverses a tunnel junction and enters multiple active regions, it can recombine multiple times, generating multiple photons.

[0099] Taking a four-junction cascade as an example, the oxide confinement layer is removed above the second and fourth active regions; the interval between the first and second active regions is 0.5λ, the interval between the second and third active regions is 1λ, and the interval between the third and fourth active regions is 0.5λ; a GaAs tunnel junction is inserted at the second node of the top DBR. Multiple active regions are connected in series to the same resonant cavity by heavily doped reverse tunnel junctions. The energy band diagram of the multi-junction cascade active region structure is shown in Figure 2. Figure 2 This structure can reduce the divergence angle and Joule heat, thereby improving the beam quality and power of the device. Figure 3 It is the current-voltage-power and current-power conversion efficiency characteristic curve. Figure 4 Far-field divergence angle diagram

[0100] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A high-power, low-divergence multi-junction cascade vertical-cavity surface-emitting laser structure, characterized by: It includes an n-GaAs substrate and an n-GaAs buffer layer, an n-distributed Bragg reflector, an n-Al 0.6- 0.3 Ga 0.4-0.7 As space layer, gain region, p-Al 0.3-0.6 Ga 0.7-0.4 As space layer, p-distributed Bragg reflector, Al 0.98 Ga 0.02 As oxide confinement layer, p-distributed Bragg reflector, GaAs tunnel junction layer, n-distributed Bragg reflector and p-GaAs cap layer, wherein: The n-GaAs buffer layer is grown on the n-GaAs substrate, the n-distributed Bragg reflector is grown on the n-GaAs buffer layer, and the n-Al 0.6-0.3 Ga 0.4-0.7 The As spacer layer is grown on the n-distributed Bragg reflector, and the gain region is grown on the n-Al 0.6- 0.3 Ga 0.4-0.7 As space layer grows, p-Al 0.3-0.6 Ga 0.7-0.4 As spacer layer is grown on the gain region, and p-distributed Bragg reflector is grown on p-Al 0.3-0.6 Ga 0.7-0.4 As space layer grows, Al 0.98 Ga 0.02 As oxide confinement layer is grown on the p-distributed Bragg reflector, which is grown on the Al 0.98 Ga 0.02 As oxide confinement layer, a GaAs tunnel junction layer is grown on the p-distributed Bragg reflector, an n-distributed Bragg reflector is grown on the GaAs tunnel junction layer, and a p-GaAs cap layer is grown on the n-distributed Bragg reflector.

2. The high-power, low-divergence multi-junction cascade vertical-cavity surface-emitting laser structure according to claim 1, characterized in that: The thickness of the n-GaAs substrate is 250 nm and the doping concentration is 3×10 18 cm -1 The thickness of the n-GaAs buffer layer is 500 nm and the doping concentration is 2×10 18 cm -1 The p-GaAs cap layer has a thickness of 5 nm and a doping concentration of 1.5×10 18 cm -1 The GaAs tunnel junction layer includes a p-GaAs tunnel junction layer and an n-GaAs tunnel junction layer, the p-GaAs tunnel junction layer has a thickness of 5nm and a doping concentration of 8×10 25 cm -1 ; The thickness of the n-GaAs tunnel junction layer is 15nm and the doping concentration is 3×10 25 cm -1 .

3. The high-power, low-divergence multi-junction cascade vertical-cavity surface-emitting laser structure according to claim 1, characterized in that: The gain region includes four active regions, with Al2O3 arranged between adjacent active regions. 0.6 Ga 0.4 As space layer, GaAs tunnel junction layer, Al 0.6 Ga 0.4 As space layer, Al is added between the two active regions in the middle of the gain region 0.6 Ga 0.4 As space layer and Al 0.98 Ga 0.02 As oxide limiting layer, Al 0.6 Ga 0.4 As space layer, Al 0.98 Ga 0.02 As oxidation restriction layer, Al 0.6 Ga 0.4 As space layer, GaAs tunnel junction layer, Al 0.6 Ga 0.4 As space layer, and the GaAs tunnel junction layer has the same structure as the GaAs tunnel junction layer grown on the p-distributed Bragg reflector.

4. The high-power, low-divergence multi-junction cascade vertical-cavity surface-emitting laser structure according to claim 3, characterized in that: The active region comprises four layers of GaAs 0.92 P 0.08 Barrier layer, three layers of In 0.16 Ga 0.84 As quantum well, GaAs 0.92 P 0.08 The barrier layer thickness is 6.2nm, In 0.16 Ga 0.84 The thickness of the As quantum well is 4.5 nm.

5. The high-power, low-divergence multi-junction cascade vertical-cavity surface-emitting laser structure according to claim 3, characterized in that: The three Al2O3 layers along the growth direction between the two active regions in the middle of the gain region 0.6 Ga 0.4 The thickness of the As space layer is 37.8nm, 121.5nm, and 40.7nm respectively. The Al 0.6 Ga 0.4 The thickness of the As spacer layer is 42 nm.

6. The high-power, low-divergence multi-junction cascade vertical-cavity surface-emitting laser structure according to claim 1, characterized in that: The n-distributed Bragg reflector near the crystal plane consists of 35.5 pairs of n-GaAs high refractive index layers and n-Al 0.9 Ga 0.1 As low refractive index layer, starting from high to low Al x Ga 1-x As composition graded layer; the n-distributed Bragg reflector away from the crystal plane includes 16.5 pairs of n-GaAs high refractive index layers and n-Al 0.9 Ga 0.1 As low refractive index layer, the starting end is n-GaAs high refractive index layer; Al inserted between the two layers of different refractive index x Ga 1-x As composition gradient layer, n-GaAs high refractive index layer thickness is 47.6nm, doping concentration is 2×10 18 cm -1 ;Al 0.9 Ga 0.1 The As low refractive index layer has a thickness of 55.7 nm and a doping concentration of 2×10 18 cm -1 ;Al x Ga 1-x The thickness of the As composition graded layer is 20 nm, and the doping concentration is 2.5×10 18 cm -1 , wherein the Al concentration x gradually changes from the high refractive index layer to the low refractive index layer in the range of 0 to 0.9, and from the low refractive index layer to the high refractive index layer in the range of 0.9 to 0; the n-distributed Bragg reflector is n-type doped; In p-Al 0.3-0.6 Ga 0.7-0.4 The p-distributed Bragg reflector grown on the As spacer is a p-Al 0.9 Ga 0.1 As low refractive index layer, doping concentration is 2×10 18 cm -1 , thickness is 62.7nm; in Al 0.98 Ga 0.02 The p-distributed Bragg reflector grown on the As oxide confinement layer is a 20nm thick Al x Ga 1-x As composition gradient layer, p-GaAs high refractive index layer with a thickness of 16.59nm, Al layer with a thickness of 20nm from high to low x Ga 1-x As composition graded layer, p-Al with a thickness of 44.04nm 0.9 Ga 0.1 As low refractive index layer and Al with thickness of 20nm from low to high x Ga 1-x As composition graded layer; p-type doping in p-distributed Bragg reflector.

7. The high-power, low-divergence multi-junction cascade vertical-cavity surface-emitting laser structure according to claim 1, characterized in that: The n-Al 0.6-0.3 Ga 0.4-0.7 The thickness of the As space layer is 123nm; the p-Al 0.3-0.6 Ga 0.7-0.4 The thickness of the As space layer is 123 nm; the Al 0.98 Ga 0.02 The thickness of the As oxide restriction layer is 30 nm.

8. A method for preparing a high-power, low-divergence multi-junction cascaded vertical-cavity surface-emitting laser, for preparing the high-power, low-divergence multi-junction cascaded vertical-cavity surface-emitting laser structure according to any one of claims 1 to 7, characterized in that: The specific steps include: Step 1. Cleaning the n-GaAs substrate surface: introducing hydrogen gas at a reaction chamber temperature of 700-740°C for 5-15 minutes to clean away particle contaminants and remove surface oxygen atoms. Step 2. n-GaAs buffer layer growth: the temperature is reduced to 650-680°C, the trimethyl gallium flow rate is 90 sccm, the arsine flow rate is 440 sccm, the silane flow rate is 50-100 sccm, the growth thickness is 500 nm, and the n-type doping concentration is 2×10 18 cm -3 ; Step 3. n-Distributed Bragg reflector growth: Growth temperature is 650-680℃, grow DBR laser structure, a total of 35.5 cycles; a DBR laser growth cycle is: from high to low Al x Ga 1-x As composition gradient layer, Al 0.9 Ga 0.1 As low refractive index layer, Al from low to high x Ga 1-x As composition graded layer and n-GaAs high refractive index layer; Step 4.Al 0.3-0.6 Ga 0.7-0.4 As space layer growth: the temperature remains unchanged, the trimethylgallium flow rate is 55 sccm, the trimethylaluminum flow rate is 125 sccm, the arsine flow rate is 440 sccm, and the growth thickness is 123 nm; Step 5. Active Area Growth: Step 5.1GaAs 0.92 P 0.08 Barrier layer: The reaction chamber temperature remains unchanged, the trimethylgallium flow rate is 45 sccm, the arsine flow rate is 800-1500 sccm, and the phosphine flow rate is 300-500 sccm; Step 5.2In 0.16 Ga 0.84 As quantum well layer: temperature raised to 680-700°C, trimethylgallium flow rate of 64 sccm, trimethylindium flow rate of 50 sccm, arsine flow rate of 1000-2000 sccm; repeat steps 5.1-5.2 three times; Step 6.Al 0.6 Ga 0.4 As space layer growth: the same growth process as step 4, the growth thickness is 42nm; Step 7. GaAs tunnel junction layer growth: p-GaAs tunnel junction layer growth: temperature dropped to 550-650°C, trimethyl gallium flow rate was 97 sccm, trimethyl aluminum flow rate was 28 sccm, arsine flow rate was 1160 sccm, carbon tetrabromide flow rate was 10-25 sccm, growth thickness was 5 nm, p-type doping concentration was 8×10 19 cm -3 n-GaAs tunnel junction layer growth: growth temperature 550-650°C, trimethylgallium flow rate 97 sccm, trimethylaluminum flow rate 28 sccm, arsine flow rate 1160 sccm, carbon tetrabromide flow rate 10-25 sccm, growth thickness 20 nm, p-type doping concentration 3×10 19 cm -3 ; Step 8.Al 0.6 Ga 0.4 As spatial layer growth: same as step 6; Active area growth: same as step 5; Al 0.6 Ga 0.4 As space layer growth: same as step 4, the growth thickness is 37.8nm; Step 9.Al 0.98 Ga 0.02 As oxide confinement layer growth: growth temperature 650-680°C, trimethylgallium flow rate 55 sccm, trimethylaluminum flow rate 125 sccm, arsine flow rate 440 sccm, carbon tetrabromide flow rate 10-25 sccm, growth thickness 30 nm, p-doping concentration 2×10 17 cm -3 ; Step 10.Al 0.6 Ga 0.4 As space layer growth: same as step 4, growth thickness is 121.5nm; GaAs tunnel junction layer growth: same as step 7; Al 0.6 Ga 0.4 As space layer growth: same as step 4, the growth thickness is 40.7nm; Active area growth: same as step 5; Al 0.6 Ga 0.4 As spatial layer growth: same as step 6; GaAs tunnel junction layer growth: same as step 7; Al 0.6 Ga 0.4 As spatial layer growth: same as step 6; Active area growth: same as step 5; Al 0.3-0.6 Ga 0.7-0.4 As space layer growth: same as step 4, growth thickness is 123nm; Step 11. p-distributed Bragg reflector growth: same as Al in step 3 0.9 Ga 0.1 The As low refractive index layer is grown using the same process, with a thickness of 62.7 nm. Al 0.98 Ga 0.02 As oxide confinement layer growth: same as step 9; p-distributed Bragg reflector growth: same as step 3 growth process, from low to high Al x Ga 1-x The thickness of the As composition gradient layer is 20nm, the thickness of the p-GaAs high refractive index layer is 16.59nm, and the Al x Ga 1-x The thickness of the As composition gradient layer is 20nm, and the p-Al 0.9 Ga 0.1 The thickness of the As low refractive index layer is 44.04nm, and the thickness of the Al x Ga 1-x The thickness of the As composition gradient layer is 20 nm; GaAs tunnel junction layer growth: same as step 7; n-Distributed Bragg reflector growth: The growth temperature is 650-680℃, and the DBR laser structure is grown for a total of 16.5 cycles. A DBR laser growth cycle is: n-GaAs high refractive index layer, Al x Ga 1-x As composition gradient layer, Al 0.9 Ga 0.1 As low refractive index layer, Al from low to high x Ga 1-x As component gradient layer; Step 12. p-GaAs cap layer growth: temperature dropped to 550-650°C, trimethylgallium flow rate was 90 sccm, arsine flow rate was 440 sccm, carbon tetrabromide flow rate was 10-25 sccm, growth thickness was 5 nm, and p-type doping concentration was greater than 1×10 19 cm -3 .

9. The method for preparing a high-power, low-divergence-angle multi-junction cascade vertical-cavity surface-emitting laser according to claim 8, characterized in that: The growth process of the DBR laser structure is as follows: From high to low Al x Ga 1-x As composition gradient layer growth: x linearly changes from 0 to 0.9, and the doping concentration is 2.5×10 18 cm -3 , thickness is 20nm; Al 0.9 Ga 0.1 As low refractive index layer growth: doping concentration is 2×10 18 cm -3 , thickness is 55.7nm; From low to high Al x Ga 1-x As composition gradient layer growth: x linearly changes from 0.9 to 0, and the doping concentration is 2.5×10 18 cm -3 , thickness is 20nm; Growth of GaAs high refractive index layer: doping concentration is 2×10 18 cm -3 , thickness is 47.6nm; In the above steps, the doping concentration is controlled by adjusting the SiH4 flow rate; n-type doping is used in the n-distributed Bragg reflector, and p-type doping is used in the p-distributed Bragg reflector.

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