A multi-junction vertical cavity surface emitting laser and a method of manufacturing the same

Abstract

The application provides a multi-junction vertical cavity surface emitting laser and a manufacturing method thereof, which comprises, from bottom to top, a substrate, a buffer layer, an N-type DBR reflection layer, a resonant cavity layer and a P-type DBR reflection layer, wherein the resonant cavity layer comprises a multi-quantum well layer, an oxidation layer and a tunnel junction layer, the tunnel junction layer comprises, from bottom to top, a P-type confinement layer, a P-type tunnel junction layer, an N-type tunnel junction layer and an N-type confinement layer, the N-type tunnel junction layer comprises at least one first N-type tunnel junction layer and at least one second N-type tunnel junction layer which are alternately stacked, the first N-type tunnel junction layer is doped with Te elements, and the second N-type tunnel junction layer is doped with Si elements; the N-type tunnel junction layer of the application is grown in an alternating doping mode, effectively reducing the diffusion of Te elements in the tunnel junction, and after the growth of the N-type tunnel junction layer, the flow of AsH3 is increased to 1000sccm-1500sccm, which can further reduce the diffusion of Te elements and ensure the steep doping at the P / N junction interface.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor lasers, and particularly relates to a multi-junction vertical cavity surface emitting laser and a manufacturing method thereof. BACKGROUND

[0002] As a kind of micro-cavity surface emitting laser, the vertical cavity surface emitting laser (VCSEL) has the characteristics of single longitudinal mode operation, low threshold current, easy integration and low cost manufacturing, and gradually receives the favor of the market, and is currently widely used in face recognition, ranging, laser radar, optical communication, medical treatment and other fields. When Vcsel is used in the fields of laser radar, ranging and the like, high power is often required. At present, the mainstream approach is to increase the light emitting area of the laser chip, but this approach is not conducive to the current trend of product miniaturization.

[0003] By using the tunnel junction technology, multiple semiconductor laser epitaxial layers can be directly connected in series during the material epitaxial process, multiple lasers can be integrated in a smaller space, and the optical power density can be effectively increased. Similarly, the vertical cavity surface emitting laser (VCSEL) can also connect multiple quantum wells in the resonant cavity through the tunnel junction to increase the optical power. Therefore, as a new round of development of VCSEL, the multi-junction VCSEL technology has become a research hotspot. The multi-junction VCSEL contains multiple cascaded active regions, which can increase the internal quantum efficiency of the device and reduce the carrier density, thereby obtaining higher gain and advantages, for example, higher efficiency can reduce the overall thermal load; higher power density greatly reduces the size of the chip and the package, thereby simplifying the optical design and system architecture.

[0004] Infrared VCSELs are usually grown on a GaAs substrate, and among them, the lasers with wavelengths of 940 nm and 850 nm are most widely used. The multi-junction infrared VCSEL connects multiple quantum wells in the resonant cavity through the tunnel junction to increase the optical power. Therefore, the structure and quality of the tunnel junction have a great influence on the performance of the entire laser device.

[0005] The tunnel junction is usually composed of a highly doped P-type semiconductor and a highly doped N-type semiconductor, and the key is to ensure that the doping concentration distribution of the P / N interface is as steep as possible to achieve efficient electron tunneling. In terms of P-type doping, C element is usually used, which is not easy to diffuse and can form a relatively steep doping ladder; in terms of N-type doping, silicon (Si) and tellurium (Te) elements are commonly used doping elements, and the Si element can reach a maximum of 9E 18 cm -3 in the epitaxial layer, but for multi-junction infrared VCSELs, the doping of the tunnel junction needs to reach at least 1E 19 cm -3The above is to achieve good tunneling performance. To obtain higher N-type doping, Te element doping is needed, which can increase the doping concentration to 1E 19 cm -3 above. However, Te element has a strong memory effect, which can cause the tunneling junction to deteriorate, and Te element diffusion is also serious, which often cannot guarantee the steep doping at the P / N junction interface, which can affect the tunneling current of the tunneling junction, and further affect the working performance of the device. Although the prior art can reduce the diffusion of Te element by reducing the doping amount, the doping amount cannot meet the requirements of the tunneling junction.

[0006] Therefore, when designing and preparing a multi-junction infrared VCSEL, the structure of the tunneling junction, the selection of the doping element and the control of the doping concentration need to be considered comprehensively to optimize the performance of the laser. SUMMARY

[0007] The purpose of the present application is to provide a multi-junction vertical cavity surface emitting laser and a manufacturing method thereof, which effectively reduces the diffusion of Te element in the tunneling junction, guarantees the steep doping at the P / N junction interface, and improves the electro-optical conversion efficiency and reliability of the multi-junction vertical cavity surface emitting laser.

[0008] To achieve the above purpose, the solution of the present application is to provide a manufacturing method of a multi-junction vertical cavity surface emitting laser, comprising:

[0009] providing a substrate, and growing a buffer layer, an N-type DBR reflection layer, a resonant cavity layer and a P-type DBR reflection layer on the substrate by using MOCVD method;

[0010] The resonant cavity layer comprises a multi-quantum well layer, an oxidation layer and a tunneling junction layer, the tunneling junction layer comprises a P-type limiting layer, a P-type tunneling junction layer, an N-type tunneling junction layer and an N-type limiting layer grown from bottom to top, the N-type tunneling junction layer comprises at least one first N-type tunneling junction layer and at least one second N-type tunneling junction layer grown alternately, the first N-type tunneling junction layer is in contact with the P-type tunneling junction layer, and the first N-type tunneling junction layer and the second N-type tunneling junction layer are both N-type Al x2 Ga 1-x2 As layer, the first N-type tunneling junction layer is doped with Te element, and the second N-type tunneling junction layer is doped with Si element;

[0011] The P-type limiting layer is a P-type Al x1 Ga 1-x1 As limiting layer, and the P-type tunneling junction layer is a P-type Al x2 Ga 1-x2As tunnel junction layer, wherein, 0.7≤x1≤1, 0≤x2≤0.4; the P-type limiting layer and the P-type tunnel junction layer further grow a P-type transition layer, the P-type transition layer is a P-type AlGaAs transition layer with nonlinear variation of Al component, so as to gradually change the P-type Al x1 Ga 1-x1 As limiting layer into a P-type Al x2 Ga 1-x2 As tunnel junction layer;

[0012] The N-type tunnel junction layer is an N-type Al x2 Ga 1-x2 As tunnel junction layer, the N-type limiting layer is an N-type Al x1 Ga 1-x1 As limiting layer, wherein, 0.7≤x1≤1, 0≤x2≤0.4; the N-type tunnel junction layer and the N-type limiting layer further have an N-type transition layer, the N-type transition layer is an N-type AlGaAs transition layer with nonlinear variation of Al component, and the gradual change is symmetrical to the P-type transition layer;

[0013] After the growth of the N-type tunnel junction layer, the flow of AsH3 in the MOCVD cavity is increased from the original 100sccm-400sccm to 1000sccm-1500sccm, the temperature in the MOCVD cavity is increased to 700-750℃, and the N-type tunnel junction layer is purged using a large gas flow for 3-5 minutes, and the total flow of the purge is 20000sccm-35000sccm.

[0014] Further, the doping amount of the first N-type tunnel junction layer is 2E 19 cm -3 to 4E 19 cm -3 , and the doping amount of the second N-type tunnel junction layer is 5E 18 cm -3 to 8E 18 cm -3 .

[0015] Further, the number of layers of the N-type tunnel junction layer is 5-10 layers.

[0016] Further, the P-type transition layer equally divides the gradual change interval of Al component into three parts, the Al component change amount of the three parts is the same, and the first part accounts for 15% of the thickness of the P-type transition layer, the second part accounts for 35% of the thickness of the P-type transition layer, and the third part accounts for 50% of the thickness of the P-type transition layer.

[0017] Further, the growth thickness of the P-type limiting layer is 50-100 nm, the growth thickness of the P-type tunnel junction layer is 10-20 nm, and the growth thickness of the P-type transition layer is 15-30 nm, and the doping elements of the three are C.

[0018] Further, the growth thickness of the N-type tunnel junction layer is 15-30 nm, the growth thickness of the N-type limiting layer is 50-100 nm, and the doping element is Si, and the growth thickness of the N-type transition layer is 15-30 nm, and the doping element is Si.

[0019] Further, the oxide layer includes a first oxide layer and a second oxide layer, and the first oxide layer and the second oxide layer are located on both sides of the tunnel junction layer, the multi-quantum well layer includes a first multi-quantum well layer and a second multi-quantum well layer, the first multi-quantum well layer is located between the N-type DBR reflection layer and the first oxide layer, and the second multi-quantum well layer is located between the second oxide layer and the tunnel junction layer.

[0020] The application also provides a multi-junction vertical cavity surface emitting laser manufactured by the manufacturing method.

[0021] After the above scheme is adopted, the application has the following advantages:

[0022] 1. The application sets the N-type tunnel junction layer as a multi-layer structure in which a first N-type tunnel junction layer and a second N-type tunnel junction layer are alternately stacked, the first N-type tunnel junction layer is doped with Te elements, the second N-type tunnel junction layer is doped with Si elements, that is, the N-type tunnel junction layer is doped in an alternating manner with Te and Si elements, in the process of growing the N-type tunnel junction layer, the Te elements in the first N-type tunnel junction layer will diffuse to the second N-type tunnel junction layer, consume a large part of the Te diffusion, at the same time, the diffused Te elements can also make up for the shortage of N-type doping elements in the second N-type tunnel junction layer, so that the high doping amount of the N-type tunnel junction layer is ensured, and the diffusion of Te elements is reduced, and the steep doping at the P / N junction interface is ensured.

[0023] 2. After the N-type tunnel junction layer is grown, the flow of AsH3 in the MOCVD cavity is immediately increased from the original 100-400 sccm to 1000-1500 sccm, the V / III ratio (the ratio of As and Ga) in the MOCVD cavity is increased, the larger the amount of As, the lower the efficiency of Te incorporation, and thus the diffusion of Te elements is further reduced, and the poisoning effect of Te on the subsequent multi-quantum well layer is inhibited without reducing the doping concentration.

[0024] 3、The application increases the temperature in the MOCVD cavity immediately while providing the flow rate of the introduced AsH3, and uses a large gas flow to purge, that is, uses high-temperature baking and gas purging of the N-type tunnel junction layer to reduce the residue of Te elements in the cavity, avoid the influence of the memory effect of Te elements on the rear multi-quantum well layer as much as possible, reduce impurity recombination, and improve the electro-optical conversion efficiency and reliability of the multi-junction vertical cavity surface emitting laser.

[0025] 4、The application is provided with an N-type transition layer between the N-type tunnel junction layer and the N-type confinement layer, and a P-type transition layer between the P-type tunnel junction layer and the P-type confinement layer, both the N-type transition layer and the P-type transition layer are non-linearly changed, which can reduce the resistance of the tunnel junction layer, effectively reduce the series resistance of the device, and further effectively improve the electro-optical conversion efficiency of the device.

[0026] 5、The Al component of the N-type transition layer and the P-type transition layer is divided into three equal parts, the first part accounts for 15% of the thickness of the P-type transition layer, the second part accounts for 35% of the thickness of the P-type transition layer, and the third part accounts for 50% of the thickness of the P-type transition layer, this gradual change increases the barrier slope of the transition layer, and reduces the tunnel junction series resistance while not reducing the confinement effect of the N-type confinement layer and the P-type confinement layer. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a structural diagram of the multi-junction vertical cavity surface emitting laser of the application.

[0028] Figure 2 It is a structural diagram of the N-type tunnel junction layer of the application.

[0029] Figure 3 It is a broken line graph of the non-linear change of the Al component of the P-type transition layer of the application.

[0030] Figure 4 It is a flowchart of the manufacturing method of the application.

[0031] REFERENCE NUMERALS:

[0032] 1, substrate; 2, buffer layer; 3, N-type DBR reflection layer; 4, resonant cavity layer; 41, first multi-quantum well layer; 42, first oxidation layer; 43, tunnel junction layer; 431, P-type confinement layer; 432, P-type transition layer; 433, P-type tunnel junction layer; 434, N-type tunnel junction layer; 4341, first N-type tunnel junction layer; 4342, second N-type tunnel junction layer; 435, N-type transition layer; 436, N-type confinement layer; 44, second multi-quantum well layer; 45, second oxidation layer; 5, P-type DBR reflection layer; 6, ohmic contact layer. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the scope of the present application, and the range of the present application includes two end values.

[0034] As Figures 1-2 shown, the present application provides a multi-junction vertical cavity surface emitting laser, comprising a substrate 1, a buffer layer 2, an N-type DBR reflection layer 3, a resonant cavity layer 4, and a P-type DBR reflection layer 5 stacked in order from bottom to top.

[0035] The resonant cavity layer 4 includes a multi-quantum well layer, an oxidation layer, and a tunnel junction layer 43. The tunnel junction layer 43 includes a P-type confinement layer 431, a P-type tunnel junction layer 433, an N-type tunnel junction layer 434, and an N-type confinement layer 436 stacked in order from bottom to top. The N-type tunnel junction layer 434 includes at least one first N-type tunnel junction layer 4341 and at least one second N-type tunnel junction layer 4342 stacked alternately. The first N-type tunnel junction layer 4341 is doped with Te elements, and the second N-type tunnel junction layer 4342 is doped with Si elements, i.e., the N-type tunnel junction layer 434 is grown in an alternating doping manner. In the growth process, the Te elements in the first N-type tunnel junction layer 4341 diffuse to the second N-type tunnel junction layer 4342, consume a large part of the Te diffusion, and at the same time, the diffused Te elements can make up for the lack of N-type doping elements in the second N-type tunnel junction layer 4342. In this way, the high doping amount of the N-type tunnel junction layer 434 is ensured, and the diffusion of Te elements is reduced to ensure the steep doping at the P / N junction interface.

[0036] It should be noted that the resonant cavity layer 4 also includes a small part of the N-type DBR reflection layer 3 and the P-type DBR reflection layer 5, but the thickness is extremely small and can be ignored.

[0037] Specifically, the N-type tunnel junction layer 434 is an N-type Al x2 Ga 1-x2 As tunnel junction layer 43, where 0≤x2≤0.4, and the thickness is 15nm-30nm, i.e., the first N-type tunnel junction layer 4341 and the second N-type tunnel junction layer 4342 are both N-type Al x2 Ga 1-x2 As layers. The doping amount of the first N-type tunnel junction layer 4341 is 2E 19 cm -3 to 4E 19 cm -3 , and the doping amount of the second N-type tunnel junction layer 4342 is 5E 18 cm-3 to 8E 18 cm -3 .

[0038] Optionally, the number of layers of the N-type tunnel junction layer 434 is 5-10 layers, i.e. the thickness of the N-type tunnel junction layer 434 is equally divided into 5-10 parts, and the first layer structure in contact with the P-type tunnel junction layer 433 is the first N-type tunnel junction layer 4341, i.e. the first layer structure grown on the P-type tunnel junction layer 433 is the first N-type tunnel junction layer 4341, then the second N-type tunnel junction layer 4342 is grown, and so on until the N-type tunnel junction 434 is grown.

[0039] Optionally, in the first N-type tunnel junction layer 4341, the Te doping amount is 2E 19 cm -3 , in the second N-type tunnel junction layer 4342, the Si doping amount is 5E 18 cm -3 , the number of layers of the N-type tunnel junction layer 434 is 8 layers, and the total doping amount of the N-type tunnel junction layer 434 can reach 1.2E 19 cm -3 by electrochemical etching test machine (ECV) test, to meet the high-doping requirement of the N-type tunnel junction layer 434.

[0040] Optionally, the P-type confinement layer 431 is a P-type Al x1 Ga 1-x1 As confinement layer, wherein 0.7≤x1≤1, the thickness is 50-100 nm, the doping element is C, and the doping amount is 1E 18 cm -3 -3E 18 cm -3 , and the P-type confinement layer 431 functions to limit impurity diffusion and impurity recombination.

[0041] Optionally, the P-type tunnel junction layer 433 is a P-type Al x2 Ga 1-x2 As tunnel junction layer, wherein 0≤x2≤0.4, the thickness is 10-20 nm, the doping element is C, and the doping amount is 1E 20 cm -3 -2E 20 cm -3 .

[0042] Optionally, a P-type transition layer 432 is further arranged between the P-type confinement layer 431 and the P-type tunnel junction layer 433, the P-type transition layer 432 is a P-type AlGaAs transition layer with nonlinear change of Al component, which gradually changes the P-type Al x1 Ga 1-x1 As confinement layer into a P-type Al x2 Ga1-x2 As a tunneling junction layer, it can reduce the resistance of the P-type tunneling junction layer 433, effectively reduce the series resistance of the device, and thus effectively improve the electro-optical conversion efficiency of the device.

[0043] Optionally, the P-type transition layer divides the gradient range of the Al component into three equal parts, with each part having the same Al component variation. However, the first part accounts for 15% of the thickness of the P-type transition layer, the second part accounts for 35% of the thickness of the P-type transition layer, and the third part accounts for 50% of the thickness of the P-type transition layer. This gradient method increases the barrier slope of the transition layer and reduces the series resistance of the tunnel junction without reducing the confinement effect of the N-type confinement layer 436 and the P-type confinement layer 431.

[0044] Optionally, the thickness of the p-type transition layer 432 is 15nm-30nm, the doping element is carbon, and the doping amount is 1E. 18 cm -3 Up to 5E 18 cm -3 .

[0045] Specifically, such as Figure 3 As shown (the horizontal axis in the figure is in nm), to specifically describe the nonlinear changes of the P-type transition layer 432, P-type Al is used as an example. x1 Ga 1-x1 The As confinement layer has x1=0.9 and a thickness of 50nm, and is a P-type Al. x2 Ga 1-x Taking a 2As tunnel junction layer with x2=0 and a thickness of 10nm as an example, and a P-type AlGaAs transition layer with a thickness of 20nm, if the amount of Al component changes from x1 to x2, then the Al component changes by 0.9. Divide the gradient range of Al component into 3 equal parts, with each part having a linear change of 0.3 Al component. The thickness of the first gradient is 3nm, accounting for 15% of the total thickness of the 20nm P-type AlGaAs transition layer; the thickness of the second gradient is 7nm, accounting for 35% of the total thickness; and the thickness of the third gradient is 10nm, accounting for 50% of the total thickness.

[0046] Optionally, the N-type confinement layer 436 is an N-type Al x1 Ga 1-x1 An As confinement layer, wherein 0.7 ≤ x1 ≤ 1, with a thickness of 50 nm-100 nm, and doped with Si with a doping amount of 1E. 18 cm -3 To 3E 18 cm -3 Its function is the same as that of the P-type confinement layer 431.

[0047] Optionally, an N-type transition layer 435 is arranged between the N-type tunnel junction layer 434 and the N-type confinement layer 436, the N-type transition layer 435 is an N-type AlGaAs transition layer with nonlinear variation of Al component, which gradually varies symmetrically with the P-type transition layer 432 and has the same effect as the P-type transition layer 432, further improving the electro-optical conversion efficiency of the device.

[0048] Optionally, the oxide layer includes a first oxide layer 42 and a second oxide layer 45, the first oxide layer 42 and the second oxide layer 45 are arranged on both sides of the tunnel junction layer 43, the multi-quantum well layer includes a first multi-quantum well layer 41 and a second multi-quantum well layer 44, the first multi-quantum well layer 41 is arranged between the N-type DBR reflection layer 3 and the first oxide layer 42, and the second multi-quantum well layer 44 is arranged between the second oxide layer 45 and the tunnel junction layer 43.

[0049] Optionally, the first oxide layer 42 is an Al 0.98 Ga 0.02 As oxide layer with a thickness of 20 nm, which functions to limit current injection, and the AlGaAs with high Al component is easy to be oxidized by water vapor to generate AlO x with good electrical insulation properties, and the refractive index of AlO x is low, which can play a role of refractive index waveguide and effectively limit the light beam. The structure and function of the second oxide layer 45 are the same as those of the first oxide layer 42. It should be noted that because the oxide layer introduces oxygen elements, there are uncertain elements, and the first oxide layer 42 and the second oxide layer 45 need to be placed at the position of the resonant cavity wave valley to minimize light attenuation.

[0050] Optionally, the first multi-quantum well layer 41 is composed of multiple groups of 8 nm InGaAs and 8 nm AlGaAs grown alternately, wherein the In component is between 0 and 0.2, and the Al component is between 0 and 0.45, and the structure of the second multi-quantum well layer 44 is the same as that of the first multi-quantum well layer 41, and both need to be placed at the position of the resonant cavity wave peak to maximize the gain.

[0051] Optionally, the substrate 1 is a GaAs substrate 1, and specifically a 2-degree GaAs substrate 1.

[0052] Optionally, the buffer layer 2 is a GaAs buffer layer 2 with a thickness of 500 nm, and the purpose of growing the buffer layer 2 is to connect the substrate 1 and the subsequently grown epitaxial layer to reduce defects of the epitaxial layer.

[0053] Optionally, the N-type DBR reflection layer 3 is a mirror structure, which comprises an adjustable multi-layer structure of two optical materials, the N-type DBR reflection layer is formed by alternately growing high Al content AlGaAs layers and low Al content AlGaAs layers, the high Al content ranges from 80% to 95%, the low Al content ranges from 0% to 55%, and there is a 20 nm transition layer between the high Al content AlGaAs layer and the low Al content AlGaAs layer, the optical thickness of the high Al content AlGaAs layer plus the transition layer is one quarter of the laser wavelength, and the optical thickness of the low Al content AlGaAs layer plus the transition layer is one quarter of the laser wavelength; the number of the N-type DBR reflection layer 3 is 50 pairs to 60 pairs, and the doping element is an N-type doping element Si. The structure of the P-type DBR reflection layer 5 is the same as that of the N-type DBR reflection layer 3, and the difference is that the number of the P-type DBR reflection layer 5 is 25 pairs to 35 pairs, and the doping element is a P-type doping element C.

[0054] Optionally, the N-type DBR reflection layer 3 is further provided with a high-doped ohmic contact layer 6, the material of the ohmic contact layer 6 is GaAs, the thickness is 20 nm, the doping element is a P-type doping element C, and the doping amount is 1E 20 cm -3 .

[0055] The application also provides a manufacturing method of a multi-junction vertical cavity surface emitting laser, which specifically adopts an organic chemical vapor phase epitaxy deposition (MOCVD) method, takes TMGa, TMIn, TMAl, PH3 and AsH3 as Ga source, In source, Al source, P source and As source, takes H2 as carrier gas, and grows a buffer layer 2, an N-type DBR reflection layer 3, a resonant cavity layer 4, a P-type DBR reflection layer 5 and an ohmic contact layer 6 on a substrate 1 from bottom to top, wherein the resonant cavity layer 4 comprises a first multi-quantum well layer 41, a first oxidation layer 42, a tunnel junction layer 43, a second multi-quantum well layer 44 and a second oxidation layer 45 grown from bottom to top, and the tunnel junction layer 43 comprises a P-type confinement layer 431, a P-type transition layer 432, a P-type tunnel junction layer 433, an N-type tunnel junction layer 434, an N-type transition layer 435 and an N-type confinement layer 436 grown from bottom to top.

[0056] Please refer to Figure 1 and Figure 4 , the manufacturing method specifically comprises the following steps:

[0057] S1, providing a substrate 1, the substrate 1 selects a 2-degree GaAs substrate 1, and a buffer layer 2 is grown on the substrate 1, the buffer layer 2 is a GaAs buffer layer 2, the growth thickness is 500 nm, and the purpose of growing the buffer layer 2 is to connect the substrate 1 and the subsequently grown epitaxial layer, and reduce the defects of the epitaxial layer.

[0058] S2, growing an N-type DBR reflection layer 3 on the buffer layer 2.

[0059] Specifically, the N-type DBR reflection layer 3 is an adjustable multilayer structure composed of two optical materials, which is formed by alternately growing high Al content AlGaAs layers and low Al content AlGaAs layers, the high Al content ranges from 80% to 95%, the low Al content ranges from 0% to 55%, and there is a 20nm transition layer between the high Al content AlGaAs layer and the low Al content AlGaAs layer, wherein the optical thickness of the high Al content AlGaAs layer plus the transition layer is one quarter of the emitted laser wavelength, and the optical thickness of the low Al content AlGaAs layer plus the transition layer is one quarter of the emitted laser wavelength; the number of pairs of the N-type DBR reflection layer 3 is 50 pairs to 60 pairs, and the doping element is an N-type doping element Si.

[0060] S3, growing a first multi-quantum well layer 41 on the N-type DBR reflection layer 3.

[0061] Specifically, the first multi-quantum well layer 41 is composed of multiple groups of 8nm InGaAs and 8nm AlGaAs alternately grown, wherein the In component is between 0 and 0.2, and the Al component is between 0 and 0.45, and the first multi-quantum well layer 41 needs to be placed at the position of the resonant cavity wave peak, so as to ensure the maximization of gain.

[0062] S4, growing a first oxidation layer 42 on the first multi-quantum well layer 41.

[0063] Specifically, the first oxidation layer 42 is an Al 0.98 Ga 0.02 As oxidation layer with a growth thickness of 20nm, which functions to limit current injection, and the high Al component AlGaAs of the first oxidation layer 42 is easy to be oxidized by water vapor to generate AlO x , which has good electrical insulation characteristics, and the refractive index of AlO x is low, which can play a role of refractive index waveguide and effectively limit the light beam. Because the oxidation layer introduces oxygen elements, there are uncertain elements, and the first oxidation layer 42 needs to be placed at the position of the resonant cavity wave valley to ensure the minimization of light attenuation.

[0064] S5, growing a tunnel junction layer 43 on the first oxidation layer 42.

[0065] Specifically, a P-type limiting layer 431 with lower doping is first grown, and the P-type limiting layer 431 is specifically a P-type Al x1 Ga 1-x1 As limiting layer, wherein 0.7≤x1≤1, the thickness is 50nm-100nm, the doping element is C, and the doping amount is 1E 18 cm -3To 3E 18 cm -3 The P-type limiting layer 431 is used to limit impurity diffusion and impurity recombination.

[0066] Then, the P-type transition layer 432 with nonlinear change of Al component is grown, which is specifically a P-type AlGaAs transition layer, with a thickness of 15-30 nm, a doping element of C element, and a doping amount of 1E 18 cm -3 To 5E 18 cm -3 The P-type transition layer 432 connects the P-type limiting layer 431 and the subsequent P-type tunnel junction layer 433, and gradually changes the P-type Al x1 Ga 1-x1 As limiting layer into the subsequent P-type Al x2 Ga 1-x2 As tunnel junction layer, which can reduce the resistance of the P-type tunnel junction layer 433, effectively reduce the series resistance of the device, and thus effectively improve the electro-optical conversion efficiency of the device.

[0067] Optionally, the P-type transition layer equally divides the gradual change interval of the Al component into three parts, each with the same change amount of Al component, the first part accounts for 15% of the growth thickness of the P-type transition layer, the second part accounts for 35% of the growth thickness of the P-type transition layer, and the third part accounts for 50% of the growth thickness of the P-type transition layer. This gradual change mode increases the barrier slope of the transition layer, and also reduces the series resistance of the tunnel junction while not reducing the limiting effect of the N-type limiting layer 436 and the P-type limiting layer 431.

[0068] Then, the P-type tunnel junction layer 433 is grown, which is specifically a P-type Al x2 Ga 1-x2 As tunnel junction layer, with 0≤x2≤0.4, a thickness of 10-20 nm, a doping element of C, and a doping amount of 1E 20 cm -3 To 2E 20 cm -3 .

[0069] Then, the N-type tunnel junction layer 434 is grown, which is specifically an N-type Al x2 Ga 1-x2 As tunnel junction layer 43, with 0≤x2≤0.4, a thickness of 15-30 nm. The N-type tunnel junction layer 434 is grown in an alternating doping manner of Si / Te, i.e., the N-type tunnel junction layer 434 is divided into multiple parts, preferably 5-10 parts, the first part is grown into the first N-type tunnel junction layer 4341, the first N-type tunnel junction layer 4341 is doped with Te element, and the doping amount is 2E 19 cm -3to 4E 19 cm -3 , the second N-type tunnel junction layer 4342 is grown, and the doping amount of the second N-type tunnel junction layer 4342 is 5E 18 cm -3 to 8E 18 cm -3 Then, the first N-type tunnel junction layer 4341 and the second N-type tunnel junction layer 4342 are repeatedly grown until the N-type tunnel junction layer 434 is grown completely. In the process of growth, the Te element in the first N-type tunnel junction layer 4341 diffuses to the second N-type tunnel junction layer 4342, consumes a large part of the Te diffusion, and at the same time, the diffused Te element can make up for the shortage of N-type doping elements in the second N-type tunnel junction layer 4342, so that the high doping amount of the N-type tunnel junction layer 434 is ensured, and the diffusion of the Te element is reduced, and the steep doping at the P / N junction interface is ensured.

[0070] It should be noted that after the N-type tunnel junction layer 434 is grown, the flow of AsH3 in the MOCVD cavity is increased from the original 100sccm-400sccm to 1000sccm-1500sccm, and the Ga source remains unchanged. This process increases the V / III ratio (the ratio of As and Ga) in the MOCVD cavity. The greater the amount of As, the lower the efficiency of Te incorporation, and thus the diffusion of Te element is further reduced. At the same time, the temperature of the MOCVD cavity needs to be immediately increased to 700-750°C, and a large gas flow is used to purge the N-type tunnel junction layer for 3-5 minutes, with a total flow of 20000-35000sccm. The gas environment in the cavity is replaced as quickly as possible, and the high temperature baking and gas purging are used to reduce the residue of Te element in the cavity and to avoid the influence of the memory effect of Te element on the rear quantum well epitaxial layer as much as possible.

[0071] After purging, the N-type transition layer 435 is grown. The N-type transition layer 435 is an N-type AlGaAs transition layer with a nonlinear change in Al composition, which gradually changes symmetrically with the P-type transition layer 432 and has the same effect as the P-type transition layer 432, further improving the electro-optical conversion efficiency of the device.

[0072] Finally, the N-type confinement layer 436 is grown. The N-type confinement layer 436 is specifically an N-type Al x1 Ga 1-x1 As confinement layer, where 0.7≤x1≤1, the thickness is 50-100nm, the doping element is Si, and the doping amount is 1E 18 cm -3 to 3E 18 cm -3 , which has the same effect as the P-type confinement layer 431.

[0073] S6, growing a second multiple quantum well layer 44 on the tunnel junction layer 43, the structure of the second multiple quantum well layer is the same as the first multiple quantum well layer 41, and both need to be placed in the position of the resonance cavity wave peak, so as to ensure the maximization of gain.

[0074] S7, growing a second oxidation layer 45 on the second multiple quantum well layer 44, the structure and function of the second oxidation layer 45 are the same as the first oxidation layer 42, and both need to be placed in the position of the resonance cavity wave valley, so as to ensure the minimization of light attenuation.

[0075] S8, growing a P-type DBR reflection layer 5 on the second oxidation layer 45, the structure of the P-type DBR reflection layer 5 is the same as the N-type DBR reflection layer 3, the difference is that the number of pairs of the P-type DBR reflection layer 5 is 25 pairs-35 pairs, and the doping element is P-type doping element C.

[0076] S9, growing an ohmic contact layer 6 on the P-type DBR reflection layer.

[0077] Optionally, the material of the ohmic contact layer 6 is GaAs, the thickness is 20 nm, the doping element is P-type doping element C, and the doping amount needs to reach 1E 20 cm -3 .

[0078] It is worth noting that the thickness of the substrate 1, the buffer layer 2, the N-type DBR reflection layer 3, the resonance cavity layer 4, the P-type DBR reflection layer 5, and the ohmic contact layer 6 shown in the drawings of the present application is only an example and does not represent the true thickness. Moreover, the true ratio between the substrate 1, the buffer layer 2, the N-type DBR reflection layer 3, the resonance cavity layer 4, the P-type DBR reflection layer 5, and the ohmic contact layer 6 is not as shown in the drawings, but only for reference.

[0079] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between various embodiments can be referred to each other.

[0080] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method of fabricating a multi-junction vertical cavity surface emitting laser, characterized by, The application relates to a multi-junction vertical cavity surface emitting laser (VCSEL) and a manufacturing method thereof. After the N-type tunnel junction layer is grown, the flow of AsH3 in the MOCVD cavity is increased from the original 100sccm-400sccm to 1000sccm-1500sccm, the temperature in the MOCVD cavity is increased to 700 DEG C-750 DEG C, and a large gas flow is used to sweep the N-type tunnel junction layer for 3-5 minutes, and the total flow of the sweeping is 20000sccm-35000sccm. The resonant cavity layer comprises a multi-quantum well layer, an oxidation layer and a tunnel junction layer, the tunnel junction layer comprises, from bottom to top, a P-type confinement layer, a P-type tunnel junction layer, an N-type tunnel junction layer and an N-type confinement layer, the N-type tunnel junction layer comprises at least one first N-type tunnel junction layer and at least one second N-type tunnel junction layer which are alternately stacked, the first N-type tunnel junction layer is in contact with the P-type tunnel junction layer, and the first N-type tunnel junction layer and the second N-type tunnel junction layer are both N-type Al x2 Ga 1-x2 As layers, the first N-type tunnel junction layer is doped with a Te element, and the second N-type tunnel junction layer is doped with a Si element. The P-type confinement layer is P-type Al x1 Ga 1-x1 As confinement layer, the P-type tunnel junction layer is P-type Al x2 Ga 1-x2 As tunnel junction layer, wherein 0.7≤x1≤1, 0≤x2≤0.4; a P-type transition layer is further grown between the P-type confinement layer and the P-type tunnel junction layer, the P-type transition layer is a P-type AlGaAs transition layer with nonlinear variation of Al component, so as to gradually change the P-type Al x1 Ga 1-x1 As confinement layer into the P-type Al x2 Ga 1-x2 As tunnel junction layer; The N-type tunnel junction layer is N-type Al x2 Ga 1-x2 As tunnel junction layer, and the N-type confinement layer is N-type Al x1 Ga 1-x1 As confinement layer, wherein 0.7≤x1≤1 and 0≤x2≤0.4; an N-type transition layer is further arranged between the N-type tunnel junction layer and the N-type confinement layer, and the N-type transition layer is an N-type AlGaAs transition layer with nonlinear variation of Al component, and the gradual variation thereof is symmetrical to the P-type transition layer. The N-type tunnel junction layer has 5-10 layers.

2. A method of fabricating a multi-junction vertical cavity surface emitting laser as claimed in claim 1, wherein: The doping amount of the first N-type tunnel junction layer is 2E 19 cm -3 to 4E 19 cm -3 The doping amount of the second N-type tunnel junction layer is 5E 18 cm -3 to 8E 18 cm -3 .

3. A method of fabricating a multi-junction vertical cavity surface emitting laser as claimed in claim 2, wherein: The P-type transition layer equally divides the gradual change interval of the Al component into three parts, the Al component changes of the three parts are the same, the first part accounts for 15% of the thickness of the P-type transition layer, the second part accounts for 35% of the thickness of the P-type transition layer, and the third part accounts for 50% of the thickness of the P-type transition layer.

4. The method of manufacturing a multi-junction vertical cavity surface emitting laser of claim 1, wherein: The growth thickness of the P-type limiting layer is 50-100 nm, the growth thickness of the P-type tunnel junction layer is 10-20 nm, the growth thickness of the P-type transition layer is 15-30 nm, and the doping elements of the three are C.

5. The method of manufacturing a multi-junction vertical cavity surface emitting laser of claim 1, wherein: The growth thickness of the N-type tunnel junction layer is 15-30 nm, the growth thickness of the N-type limiting layer is 50-100 nm, and the doping element is Si; the growth thickness of the N-type transition layer is 15-30 nm, and the doping element is Si.

6. The method of manufacturing a multi-junction vertical cavity surface emitting laser of claim 1, wherein: The oxidation layer comprises a first oxidation layer and a second oxidation layer, the first oxidation layer and the second oxidation layer are located on both sides of the tunnel junction layer, the multi-quantum well layer comprises a first multi-quantum well layer and a second multi-quantum well layer, the first multi-quantum well layer is located between the N-type DBR reflection layer and the first oxidation layer, and the second multi-quantum well layer is located between the second oxidation layer and the tunnel junction layer.

7. The method of manufacturing a multi-junction vertical cavity surface emitting laser of claim 1, wherein: The application relates to a multi-junction vertical cavity surface emitting laser (VCSEL) and a manufacturing method thereof.

8. A multi-junction vertical cavity surface emitting laser, characterized by: ​

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