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CN-122026227-A - Preparation method of single-mode semiconductor laser epitaxial wafer with asymmetric waveguide structure and epitaxial wafer

CN122026227ACN 122026227 ACN122026227 ACN 122026227ACN-122026227-A

Abstract

The invention provides a preparation method of a single-mode semiconductor laser epitaxial wafer with an asymmetric waveguide structure and an epitaxial wafer, which belong to the technical field of photoelectrons, a GaAs substrate is subjected to high-temperature heat treatment in arsine-containing atmosphere, then a GaAs buffer layer, an N-side limiting layer, an N-side waveguide layer, an N-side barrier layer, a quantum well layer and a P-side barrier layer are sequentially grown on the substrate at a specific temperature, after the growth of the P-side barrier layer is completed, a P-side waveguide layer, a first P-side limiting layer, a first gradual change coupling layer, a second gradual change coupling layer and a second P-side limiting layer are sequentially grown, and finally a GaAs ohmic contact layer is grown on the second P-side limiting layer. By designing an asymmetric waveguide structure and inserting a special coupling waveguide layer, the single-mode characteristic is enhanced, the side mode rejection ratio and the optical fiber coupling efficiency are improved, the optical field loss is reduced by adopting an asymmetric structure design, the internal quantum efficiency is improved, the carrier transmission is optimized by adopting a gradient doping design, and the photoelectric performance of the device is further improved.

Inventors

  • ZHU KAI
  • ZHAO KAIDI
  • ZHU ZHEN
  • LIU CHUNHUA
  • LIU FEI

Assignees

  • 山东华光光电子股份有限公司

Dates

Publication Date
20260512
Application Date
20260112

Claims (10)

  1. 1. The preparation method of the single-mode semiconductor laser epitaxial wafer with the asymmetric waveguide structure is characterized by comprising the following steps of: s101, providing a GaAs substrate, and carrying out high-temperature heat treatment on the GaAs substrate in an arsine-containing atmosphere; S102, growing a GaAs buffer layer on the GaAs substrate at a first temperature in response to completion of the heat treatment; s103, in response to the completion of the growth of the GaAs buffer layer, growing an N-side limiting layer on the GaAs buffer layer at a second temperature, wherein the N-side limiting layer is made of a first AlGaAs material; S104, growing an N-side waveguide layer on the N-side limiting layer at a second temperature, wherein the N-side waveguide layer is made of a second AlGaAs material; s105, in response to the completion of the growth of the N-side waveguide layer, growing an N-side barrier layer on the N-side waveguide layer at a third temperature, wherein the N-side barrier layer is made of a first gallium arsenide phosphide material; s106, in response to the completion of the growth of the N side barrier layer, growing a quantum well layer on the N side barrier layer at a third temperature, wherein the quantum well layer is made of InGaAs material; S107, in response to the completion of the growth of the quantum well layer, growing a P side barrier layer on the quantum well layer at a third temperature, wherein the P side barrier layer is made of a second gallium arsenide phosphide material; S108, in response to the completion of the growth of the P side barrier layer, the following substeps are sequentially executed: S1081, growing a P side waveguide layer on the P side barrier layer at the second temperature, wherein the P side waveguide layer is made of a third AlGaAs material; S1082, growing a first P side limiting layer on the P side waveguide layer at a fourth temperature, wherein the first P side limiting layer is made of a fourth AlGaAs material; S1083, growing a first graded coupling layer on the first P side limiting layer at a fourth temperature, wherein the first graded coupling layer is made of a fifth AlGaAs material; s1084, growing a second graded coupling layer on the first graded coupling layer at a fourth temperature, wherein the second graded coupling layer is made of a sixth AlGaAs material; S1085, growing a second P side limiting layer on the second graded coupling layer at the fourth temperature, wherein the second P side limiting layer is made of a seventh AlGaAs material; And S1086, growing a GaAs ohmic contact layer on the second P side limiting layer at a fifth temperature.
  2. 2. The method for preparing a single-mode semiconductor laser epitaxial wafer with an asymmetric waveguide structure according to claim 1, wherein S101 specifically comprises the following steps: Placing the GaAs substrate on a base in an MOCVD reaction chamber, introducing hydrogen into the reaction chamber as carrier gas, and raising the temperature of the reaction chamber from room temperature to 450-500 ℃; introducing arsine gas into the reaction chamber under the condition of maintaining hydrogen atmosphere and 450-500 ℃; Raising the temperature of the reaction chamber from 450-500 ℃ to 795-815 ℃; Maintaining the GaAs substrate for 35-45 minutes at 795-815 ℃ under a continuous arsine atmosphere; After the hold is completed, the reaction chamber temperature is reduced from 795-815 ℃ to the first temperature required for the next growth step.
  3. 3. The method for preparing a single-mode semiconductor laser epitaxial wafer with an asymmetric waveguide structure according to claim 1, wherein S102 specifically comprises the following steps: Reducing the temperature of the reaction chamber from the high temperature after heat treatment to a first temperature within a 685 + -10 ℃ interval at a rate of no more than 45 ℃ per minute, and maintaining the first temperature until the temperature fluctuation is less than + -1 ℃; Simultaneously introducing trimethylgallium, arsine and a doping agent disilane into a reaction chamber, wherein the molar flow rate of the trimethylgallium is controlled within the range of 1.5 multiplied by 10 -5 to 2.5 multiplied by 10 -5 mol/min, and the molar flow rate ratio of the arsine to the trimethylgallium is maintained between 25:1 and 40:1; The GaAs is epitaxially grown on the surface of the substrate at a growth rate of 0.8-1.2nm/s under the condition that the pressure of the reaction chamber is kept at 100+/-5 mbar, so that the initial 50nm thickness of the buffer layer is formed; after the initial 50nm thickness growth is completed, the flow rate of disilane is increased to 120% of the target flow rate from an initial value in a step-like manner, and the disilane is restored to the target flow rate after being maintained for 30 seconds; and continuing to grow until the total thickness of the buffer layer reaches 250-350nm, closing the gas paths of the trimethylgallium and the disilane, keeping the arsine flow unchanged, and maintaining the arsine atmosphere at the first temperature for 30 seconds.
  4. 4. The method for preparing a single-mode semiconductor laser epitaxial wafer with an asymmetric waveguide structure according to claim 1, wherein S103 specifically comprises the following steps: The temperature of the reaction chamber is programmed to rise from the first temperature to a second temperature within a range of 720+/-10 ℃ at a rate of not higher than 45 ℃ per minute, and the temperature is judged to be stable when the temperature difference between the center and the edge of the reaction chamber is less than 2 ℃ and the temperature fluctuation is less than +/-0.5 ℃; Synchronously starting gas paths of trimethylaluminum, trimethylgallium, arsine and a dopant disilane in the reaction chamber while stabilizing the temperature, wherein the molar flow ratio of trimethylaluminum to trimethylgallium is determined according to a target aluminum component x1 through a pre-calibrated curve, and the total molar flow ratio of arsine to a III-group source is controlled between 35:1 and 45:1; Maintaining the pressure of the reaction chamber at 100+/-3 mbar, and finely adjusting the flow of trimethylaluminum by monitoring the cycle reverse growth rate of laser interference fringes in real time to ensure that the growth rate of Alx1Ga1-x1As is stabilized at 0.65+/-0.05 nm/s, and continuously growing until the thickness reaches 200nm; When the thickness reaches 200nm, the disilane flow is linearly reduced to 75% of the original set value within 2 seconds, the flow is kept to continue growing, the trimethylaluminum flow is slowly lifted according to the slope of increasing 1.5% every 100nm of growth, and the aluminum component x1 is gradually increased by 0.02 from the initial value; when the total growth thickness reaches 1.4 mu m, on the premise of maintaining the arsine flow, firstly closing the trimethylaluminum and trimethylgallium gas paths, closing the disilane gas paths after delaying for a preset time, and then maintaining the arsine atmosphere at 720 ℃ for 90 seconds.
  5. 5. The method for preparing a single-mode semiconductor laser epitaxial wafer with an asymmetric waveguide structure according to claim 1, wherein S104 specifically comprises the following steps: maintaining the reaction chamber at a second temperature and arsine atmosphere, linearly increasing the flow of trimethylaluminum from zero to an initial set value FAl in 15 seconds, calculating according to a target initial aluminum component, setting the trimethylgallium flow to a corresponding value FGa0, and starting a gas circuit; Before the thickness reaches 50nm, controlling the trimethylaluminum flow FAl (t) to decrease along with time according to a preset error function curve, and setting the decreasing time constant tau to 180 seconds so as to enable the aluminum component to smoothly transition from a starting value to a target lower limit value; Dynamically increasing the total molar flow ratio of arsine to the group III source from an initial 40:1 to 55:1 during the decreasing of the aluminum component, the increasing rate maintaining a synchronous proportional relationship with the decreasing rate of the aluminum component; when the waveguide layer grows to the total thickness of 150nm, suspending the decreasing procedure of the trimethylaluminum flow, stabilizing the flow at the current value and keeping growing for 30nm to form an interlayer; after the interlayer growth is completed, continuously decreasing the flow of the trimethylaluminum to be close to zero value according to an exponential decay curve in the residual growth thickness, finally reducing the aluminum component to be less than 0.02 at the interface of the waveguide layer and the barrier layer, and then closing a trimethylaluminum gas circuit to prepare for entering the next temperature step.
  6. 6. The method for preparing a single-mode semiconductor laser epitaxial wafer with an asymmetric waveguide structure according to claim 1, wherein S105 specifically comprises the following steps: Reducing the temperature of the reaction chamber from the second temperature to 720+/-10 ℃ at a speed of 30 ℃ per minute to a third temperature, keeping the arsine flow to 80% of that during growth in the temperature reduction process, and recovering the arsine flow to a standard value after the temperature is stable; Synchronously introducing trimethyl gallium and arsine into a reaction chamber, growing a GaAs initial layer with the thickness of 2nm, then linearly increasing the phosphane flow from zero to a target value FPH3 in 20 seconds under the condition of keeping the trimethyl gallium flow unchanged, and synchronously and initially and linearly reducing the arsine flow from an initial value FAsH to FAsH to finally ensure that the total molar flow of the V group is kept unchanged; Keeping the flow of trimethyl gallium, phosphane and arsine stable, stabilizing the phosphorus component y1 in a target interval of 0.15-0.35 by controlling the partial pressure ratio of the phosphane to the arsine, and growing a barrier layer main body at the rate of 0.9-1.1nm/s until the total thickness reaches 12nm; When the thickness reaches 12nm, the flow rate of the phosphane is reduced to 70% of the original value in 1 second, and the flow rate is kept to continue growing for 3nm, so that a local concave region of the phosphorus component is formed; after the growth of the partial concave region is completed, the phosphane flow is restored to the original target value within 2 seconds, the growth is continued until the total thickness of the barrier layer reaches 15nm, then the trimethyl gallium and the phosphane gas circuit are closed at the same time, only the arsine atmosphere is reserved, and the temperature is maintained at 680 ℃ for waiting for the subsequent steps.
  7. 7. The method for preparing a single-mode semiconductor laser epitaxial wafer with an asymmetric waveguide structure according to claim 1, wherein S106 specifically comprises the following steps: Closing a phosphine gas inlet valve, gradually increasing the flow of AsH 3 from 50sccm to 200sccm, and simultaneously introducing mixed gas of trimethyl indium and trimethyl gallium, wherein the molar ratio is set to be 0.1:0.9-0.25:0.75; Raising the temperature of the reaction chamber from 680 ℃ to 690+/-5 ℃ at a speed of 5 ℃ per minute, wherein the temperature is raised In two stages, namely, the surface diffusion capacity of In atoms is activated at a speed of 2 ℃ per minute In the first stage, and the thermal field is stabilized at a speed of 3 ℃ per minute In the second stage; The molar ratio of TMIn to TMGa is controlled by a mass flow controller, and the thickness of each 2nm is increased by 0.015 corresponding to y 2 , so that the gradient change of In components is realized; Adopting a pulse type air supply strategy, alternately introducing TMIn/TMGa mixed gas and pure AsH 3 every 3 seconds, wherein the pulse period ratio is 2:1 so as to enhance the In atom surface mobility; and monitoring the refractive index change of the film In real time by an In-situ ellipsometer, and judging that the In component reaches a target gradient when the refractive index n value is reduced from 2.88 to 2.75, and triggering a growth termination signal.
  8. 8. The method for preparing a single-mode semiconductor laser epitaxial wafer with an asymmetric waveguide structure according to claim 1, wherein S107 specifically comprises the following steps: setting the flow rate of trimethylgallium to be the same as the last stage of quantum well growth under the conditions of finishing the quantum well layer growth and maintaining arsine atmosphere and a third temperature, and keeping the state for 10 seconds to carry out surface arsenic treatment; Maintaining the trimethylgallium and arsine flows unchanged, introducing phosphane into the reaction chamber, increasing the flow from zero to a first target value FPH31 in a quadratic curve manner in 15 seconds, and simultaneously reducing the arsine flow from the current value to FAsH in a complementary quadratic curve manner, wherein the total group V molar flow is kept constant; After the phosphane flow reached the FPH31, this flow was maintained for 4nm, after which the phosphane flow was continued to increase in a linear fashion to a higher second target value FPH32 within 5 seconds while increasing the reaction chamber pressure from 95mbar to 105mbar; after stable growth is carried out for 7nm under the flow rate of FPH32, the flow rate of phosphane is reduced to 50% of the original FPH31 value in a slow linear slope of 20 seconds, and in the process of the slope reduction, a low-flow carbon doping source is synchronously introduced into a reaction chamber, wherein the flow rate is in direct proportion to the instantaneous rate of the reduction of the phosphane flow rate; after the phosphane flow is reduced to the target, the gas paths of the trimethylgallium and the phosphane are closed at the same time, the pressure of the reaction chamber is restored to 100mbar within 2 seconds, the arsine atmosphere is kept at 680 ℃ and the preparation is made for the next temperature rise and growth of the P-side waveguide layer.
  9. 9. The single-mode semiconductor laser epitaxial wafer with the asymmetric waveguide structure is characterized by being prepared by adopting the preparation method according to any one of claims 1 to 8, and comprising a GaAs substrate; sequentially grown on the GaAs substrate: a GaAs buffer layer; The N side limiting layer is made of a first AlGaAs material; The N side waveguide layer is made of a second AlGaAs material; The N side barrier layer is made of a first gallium arsenide phosphide material; The quantum well layer is made of InGaAs material; the P side barrier layer is made of a second gallium arsenide phosphide material; The P side waveguide layer is made of a third AlGaAs material; The P side limiting structure comprises a first P side limiting layer, a second P side limiting layer and a third P side limiting layer, wherein the first P side limiting layer is made of a fourth AlGaAs material; the first gradual change coupling layer is made of a fifth AlGaAs material; the second gradual change coupling layer is made of a sixth AlGaAs material; The second P side limiting layer is made of a seventh AlGaAs material; A GaAs ohmic contact layer; the N-side waveguide layer is a graded component layer, and the first graded coupling layer and the second graded coupling layer are graded component layers.
  10. 10. The single-mode semiconductor laser epitaxial wafer of claim 9, wherein the first aluminum gallium arsenide material is Alx1Ga1-x1As, wherein 0.2 ∈x1 ∈0.4; the second AlGaAs material is Alx1-x2Ga1- (x 1-x 2) As, wherein x2 is more than or equal to 0.1 and less than or equal to 0.15; The first gallium arsenide phosphide material is GaAsy P1-y1, wherein y1 is more than or equal to 0.15 and less than or equal to 0.35, and the second gallium arsenide phosphide material is GaAsy P1-y3, wherein y3 is more than or equal to 0.5 and less than or equal to 0.8; The quantum well layer is made of Iny Ga1-y2As, wherein y2 is more than or equal to 0.1 and less than or equal to 0.25; The third AlGaAs material is Alx3Ga1-x3As, wherein x3 is more than or equal to 0.12 and less than or equal to 0.16; The fourth AlGaAs material is Alx4Ga1-x4As, and the seventh AlGaAs material is Alx6Ga1-x6As, wherein x4 is more than or equal to 0.45 and less than or equal to 0.65,0.45 and x6 is more than or equal to 0.65; The fifth AlGaAs material is Alx4-x5Ga1- (x 4-x 5) As, and the sixth AlGaAs material is Alx5-x6Ga1- (x 5-x 6) As, wherein x5 is more than or equal to 0.2 and less than or equal to 0.4.

Description

Preparation method of single-mode semiconductor laser epitaxial wafer with asymmetric waveguide structure and epitaxial wafer Technical Field The invention belongs to the technical field of photoelectrons, and particularly relates to a preparation method of a single-mode semiconductor laser epitaxial wafer with an asymmetric waveguide structure and the epitaxial wafer. Background Under the background of rapid development of ultra-high-speed and high-capacity optical fiber communication, the coupling problem of a pump laser and an optical fiber is increasingly emphasized. The single-mode semiconductor laser is used as a core pump source in an optical fiber communication system, and the performance of the single-mode semiconductor laser has a decisive influence on the coupling effect. The high single-mode control capability can avoid coupling mismatch caused by multimode competition, reduce mode mismatch during coupling and improve coupling efficiency, and simultaneously can reduce interference of mode noise on coupling quality, wherein high single-mode control capability means that the mode purity is high, laser energy is concentrated in a fundamental mode, the mode noise of a signal after coupling is extremely low, and the signal to noise ratio of the signal is improved. The laser ensuring the stable operation of the fundamental mode is a basic condition for realizing high-efficiency coupling with the optical fiber, and the vertical divergence angle can be reduced by improving the compression divergence angle of the structural design and improving the light beam symmetry, in particular to a GaAs-based 940nm semiconductor laser, so that the coupling efficiency is directly improved, and the loss and the shaping difficulty in the coupling process are reduced. In the epitaxial structure of the 940nm single-mode semiconductor laser in the related art, in order to ensure the single-mode characteristics, the optical field limitation needs to be enhanced, but the too strong optical field limitation can cause the undersize of the near-field light spots and the too large divergence angle of the far-field light beams, the optical field is not matched with the mode field of the conventional optical fiber, the optical fiber coupling efficiency is difficult to improve, the light spot conversion assembly needs to be additionally added in practical application, and the complexity of the system is increased. In the related art, the optical field is regulated and controlled through waveguide design, and the differential loss of a high-order mode and a fundamental mode cannot be realized. The high-order mode is easy to generate lasing competition due to overlapping of light field distribution, so that the side mode rejection ratio is reduced, the single-mode working stability is poor, and mode jump is easy to occur particularly under high-power driving. In the symmetrical waveguide structure, the optical field is uniformly distributed on the P side and the N side, but the carrier loss of the P side limiting layer and the contact layer is far higher than that of the N side, so that the optical field is easy to generate extra absorption loss in the distribution area of the P side. Disclosure of Invention The invention provides a preparation method of a single-mode semiconductor laser epitaxial wafer with an asymmetric waveguide structure, which widens a fundamental mode light field through the asymmetric waveguide and a gradual change structure, increases near-field light spots, reduces divergence angles, introduces selective loss to a high-order mode by utilizing a coupling layer, strengthens single-mode characteristics, and improves side-mode rejection ratio and optical fiber coupling efficiency. The method comprises the following steps: s101, providing a GaAs substrate, and carrying out high-temperature heat treatment on the GaAs substrate in an arsine-containing atmosphere; S102, growing a GaAs buffer layer on the GaAs substrate at a first temperature in response to completion of the heat treatment; s103, in response to the completion of the growth of the GaAs buffer layer, growing an N-side limiting layer on the GaAs buffer layer at a second temperature, wherein the N-side limiting layer is made of a first AlGaAs material; S104, growing an N-side waveguide layer on the N-side limiting layer at a second temperature, wherein the N-side waveguide layer is made of a second AlGaAs material; s105, in response to the completion of the growth of the N-side waveguide layer, growing an N-side barrier layer on the N-side waveguide layer at a third temperature, wherein the N-side barrier layer is made of a first gallium arsenide phosphide material; s106, in response to the completion of the growth of the N side barrier layer, growing a quantum well layer on the N side barrier layer at a third temperature, wherein the quantum well layer is made of InGaAs material; S107, in response to the completion of the growth of the quantum well la