A method for calibrating growth parameters of a strain-compensated quantum cascade laser material

Abstract

The present application relates to a kind of growth parameter calibration methods of strain compensation quantum cascade laser material, the active region of the quantum cascade laser material In x Ga 1‑x As / In y Al 1‑y As multi-quantum well, wherein 0.53 < x < 1, 0 < y < 0.52, by growing InGaAs debugging structure, InGaAs calibration structure, InAlAs debugging structure, InAlAs calibration structure, obtain growth parameter In x Ga 1‑x As growth rate and In y Al 1‑ y As growth rate.The method of the present application grows strain compensation InGaAs / InAlAs quantum cascade laser material, and the epitaxial efficiency and accuracy are improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of semiconductor laser, in particular to a growth parameter calibration method of strain-compensated quantum cascade laser material. BACKGROUND

[0002] Quantum cascade laser (QCL) is a unipolar semiconductor laser based on inter-subband electron transition in semiconductor multiple quantum well, whose wavelength can cover 3-20 μm mid-infrared band and 60-300 μm terahertz band. Its main applications are environmental monitoring, space communication, infrared countermeasure, biomedical diagnosis, etc. For the design and growth of QCL active region, strain-compensation technology can effectively increase the conduction band step and reduce the threshold current density, which is one of the most effective means for developing high-performance quantum cascade laser.

[0003] The active region of mid-infrared QCL usually adopts InP-based InGaAs / InAlAs multiple quantum well periodic structure. The components matched with InP lattice are In 0.53 Ga 0.47 As and In 0.52 Al 0.48 As. Strain-compensation technology is to use lattice-mismatched In x Ga 1-x As (x>0.53) and In y Al 1-y As (y<0.52) to form multiple quantum wells to increase the conduction band step. With InP as substrate, In x Ga 1-x As (x>0.53) and In y Al 1-y As (y<0.52) materials produce compressive stress and tensile stress, respectively. Through reasonable design, the stresses of the two materials in the active region offset each other, and the total stress is greatly reduced or even 0. Strain-compensation technology can effectively improve the performance of the laser, but it poses a challenge to material growth. When the thickness of the lattice-mismatched material exceeds the critical value, the lattice relaxes and releases the stress, and the material quality also deteriorates. In addition, it is also difficult to accurately characterize the composition of the mismatched material. Therefore, growing high-quality mismatched InGaAs and InAlAs materials and accurately characterizing their composition is a difficult problem for strain-compensated quantum cascade laser material growth.

[0004] One debugging and calibration method is to grow lattice partially relaxed InGaAs and InAlAs single layer materials, and to obtain information of epitaxial layer strain, relaxation and composition by three-axis two-dimensional mapping XRD test of inverse space, however, this test is time-consuming, the material lattice quality is poor, and the analysis error of test result is large. Another debugging and calibration method is to grow InGaAs / InAlAs multi-quantum well material with lattice matched composition of substrate, and then to grow strain-compensated InGaAs / InAlAs multi-quantum well material by adjusting the composition for multiple times. The material thickness and composition information are analyzed by XRD characterization. However, the InGaAs / InAlAs multi-quantum well involves many variables, and the XRD fitting result is not unique, which makes the uncertainty of growth parameter debugging and calibration large. SUMMARY

[0005] In view of the defects of the prior art, the technical problem to be solved by the present application is to provide a growth parameter calibration method of strain-compensated quantum cascade laser material.

[0006] The growth parameter calibration method of strain-compensated quantum cascade laser material of the present application, the active region of the quantum cascade laser material is In x Ga 1-x As / In y Al 1-y As multi-quantum well, wherein 0.53 < x < 1, 0 < y < 0.52, the growth parameter In source temperature, Ga source temperature, Al source temperature, In x Ga 1-x As growth rate and In y Al 1-y As growth rate are obtained by growing InGaAs debugging structure, InGaAs calibration structure, InAlAs debugging structure and InAlAs calibration structure, so as to realize accurate growth of quantum cascade laser material.

[0007] The InGaAs debugging structure is: growing low-stress In x Ga 1-x As / InP superlattice with large proportion of InP on InP substrate, wherein In x Ga 1-x As is 2-6 nm, InP is 40-60 nm, and the period is 10-20. This structure is not easy to relax lattice, but since the proportion of InGaAs is small, the error of InGaAs parameters obtained by XRD characterization analysis is large, so this structure can only be used for preliminary debugging of InGaAs parameters. The In x Ga 1-x As and InP are grown at the same In source temperature, so the In x Ga 1-xThe growth rates of As and InP are related, and their ratio is r. InGaAs :r InP =(1+ε InGaAs ) / x, where r represents the growth rate and ε represents the lattice mismatch, and then according to r InGaAs Select 0.4–1 μm / h, and set the debugging structures InP and In. x Ga 1-x As growth time. By adjusting the In source temperature and Ga source temperature, the peak position of the superlattice diffraction peak in the XRD characterization curve of the grown material is made close to the peak position of the superlattice diffraction peak in the InGaAs debugging structure simulation curve. The peak position deviation of the 0th order diffraction peak is less than 20 arcseconds, and the period deviation of the superlattice diffraction peak position is less than 5%, thereby fixing the In source temperature and initially determining the Ga source temperature.

[0008] The InGaAs calibration structure is: a fully strain-compensated InGaAs structure is grown on an InP substrate. x Ga 1-x As / GaAs superlattice, period 30-50, In x Ga 1-x The thickness d of the As layer InGaAs The thickness of the GaAs layer is 5–15 nm. GaAs =-d InGaAs (ε InGaAs / ε GaAs ), where ε is the lattice mismatch. Used to accurately obtain the Ga source temperature and In... x Ga 1-x As the growth rate is affected, this structure is prone to lattice relaxation if the composition is not properly controlled, which can affect the lattice quality and calibration analysis of the material. Therefore, it is necessary to first perform the above-mentioned treatment on In... x Ga 1-x Preliminary adjustment of As components. Growth of In x Ga 1-x When using As and GaAs, the Ga source temperature is the same, therefore In x Ga 1-x The growth rates of As and GaAs are related, and their ratio is r. InGaAs :r GaAs =a InGaAs :(1-x)a GaAs =(1+ε InGaAs ) / ((1+ε GaAs (1-x)), where r represents the growth rate and a represents the lattice constant. Therefore, in the calibration structure, In x Ga 1-x There is also a certain proportional relationship between the growth times of As and GaAs, t InGaAs :t GaAs =ε GaAs (1+ε GaAs(x-1) / (ε InGaAs (1+ε InGaAs During material growth, first calculate and set the Ga source temperature, InGaAs growth time, and GaAs growth time based on the parameters adjusted in the previous InGaAs step. Then, precisely adjust the Ga source temperature and InGaAs growth time. x Ga 1-x The growth time of As (and correspondingly the growth time of GaAs) is adjusted to ensure that the XRD characterization curve of the grown material and the superlattice diffraction peak position of the calibrated structure simulation curve are consistent. This allows for accurate determination of the Ga source temperature and In... x Ga 1-x As growth rate.

[0009] The InAlAs conditioning structure is as follows: low-stress In with a high InP content is grown on an InP substrate. y Al 1-y As / InP superlattice, where In y Al 1-y As 2~6nm, InP 40~60nm, period 10~20. y Al 1-y The growth rates of As and InP are related, and their ratio is r. InAlAs :r InP =(1+ε InAlAs ) / y, where r represents the growth rate and ε represents the lattice mismatch. Based on the InP growth rate in the InGaAs debug structure, the growth time for each layer of the InAlAs debug structure is set. By adjusting the Al source temperature, the peak positions of the superlattice diffraction peaks in the XRD characterization curve of the grown material are made close to those in the simulated InAlAs debug structure superlattice diffraction peaks. The deviation of the 0th-order diffraction peak position is less than 20 arcseconds, and the period deviation of the superlattice diffraction peak position is less than 5%, thus initially determining the Al source temperature and In... y Al 1-y As growth rate.

[0010] The InAlAs calibration structure is as follows: Fully strain-compensated In is grown on an InP substrate. y Al 1-y As / InAs superlattice, period 30–50, where In y Al 1-y As thickness d InAlAs The thickness of the InAs layer is 5–15 nm. InAs =-d InAlAs (ε InAlAs / ε InAs ), where ε is the lattice mismatch. The growth rate is greater than r. InAlAs :r InAs =a InAlAs :yaInAs = (1 + epsilon InAlAs ) / (y(1 + epsilon InAs )), so the In y Al 1-y As growth time ratio t InAlAs : t AlAs = - epsilon InAs (1 + epsilon InAs )y / (epsilon InAlAs (1 + epsilon InAlAs )). According to the InAlAs growth parameters in the last step, the Al source temperature and InAlAs growth time and InAs growth time are calculated and set. Then the Al source temperature, In y Al 1-y As growth time (the corresponding InAs growth time is also changed) are adjusted accurately, so that the XRD characterization curve of the grown material and the superlattice diffraction peak of the simulation curve of the calibration structure are consistent. Thus the Al source temperature and In y Al 1-y As growth rate are accurately obtained.

[0011] The InGaAs calibration structure is grown after the InGaAs debugging structure, and the InAlAs debugging structure and the InAlAs calibration structure are grown after the InAlAs debugging structure, or the InAlAs debugging structure and the InAlAs calibration structure are grown after the InGaAs debugging structure and the InGaAs calibration structure.

[0012] The strain-compensated quantum cascade laser material is grown on an InP substrate by setting a growth program through the confirmed growth parameters.

[0013] The strain-compensated quantum cascade laser material is applied to the development of a laser emitting a mid-infrared waveband laser.

[0014] The strain-compensated quantum cascade laser material is applied to gas detection or infrared countermeasures.

[0015] The application provides a new strain compensation quantum cascade laser material growth method. First, a low-stress InGaAs / InP superlattice and an InAlAs / InP superlattice adjustment structure with a large InP proportion are grown on an InP substrate, source furnace temperatures are adjusted to make InGaAs and InAlAs components and growth rates close to the adjustment structure, so that the In source temperature is fixed, and the Ga source and Al source temperatures are coarsely adjusted. Then, a completely strain-compensated InGaAs / GaAs superlattice and an InAlAs / InAs superlattice calibration structure are grown, and the Ga source and Al source temperatures and material growth rates and other parameters are accurately obtained. Finally, strain-compensated quantum cascade laser material is grown according to the calibrated source furnace temperatures and material growth rates and other parameters. This method calibrates material components and obtains material growth rates by growing four adjustment and calibration structures, and has the advantages that the lattice relaxation probability of the four structure materials is greatly reduced during epitaxy, and the XRD characterization fitting results of each structure are unique. The epitaxial efficiency and accuracy of the strain-compensated InGaAs / InAlAs quantum cascade laser material grown by the method are improved.

[0016] Advantages

[0017] The four adjustment structure materials used in the application have greatly reduced lattice relaxation rates, and the XRD characterization fitting results of each structure are unique.

[0018] The method improves the epitaxial efficiency and accuracy of the strain-compensated InGaAs / InAlAs quantum cascade laser material. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a strain-compensated terahertz quantum cascade laser material growth flowchart.

[0020] Figure 2 It is an InGaAs adjustment structure XRD simulation curve, in which S represents a substrate diffraction peak, and numbers represent superlattice diffraction peaks.

[0021] Figure 3 It is an InGaAs calibration structure XRD simulation curve, in which S represents a substrate diffraction peak, and numbers represent superlattice diffraction peaks.

[0022] Figure 4 It is an InAlAs adjustment structure XRD simulation curve, in which S represents a substrate diffraction peak, and numbers represent superlattice diffraction peaks.

[0023] Figure 5 It is an InAlAs adjustment structure XRD simulation curve, in which S represents a substrate diffraction peak, and numbers represent superlattice diffraction peaks. DETAILED DESCRIPTION

[0024] The application will be further described in connection with the following specific examples. It should be understood that these examples are intended to illustrate the application and are not intended to limit the scope of the application. Furthermore, it should be understood that various modifications and changes can be made to the application by those skilled in the art upon reading the contents of this specification, which are intended to be within the scope of the application.

[0025] Example 1

[0026] A method for growing a strain-compensated quantum cascade laser material is provided, and the steps are as follows:

[0027] (1) A strain-compensated 4.6 μm mid-infrared quantum cascade laser material structure is provided, and the active region is In 0.67 Ga 0.33 As / In 0.37 Al 0.63 As multi-quantum well. The main parameters to be determined for material growth are the In source temperature, the Ga source temperature, the Al source temperature, the In 0.67 Ga 0.33 As growth rate, and the In 0.37 Al 0.63 As growth rate.

[0028] (2) An In 0.67 Ga 0.33 As / InP superlattice adjustment structure is grown on an InP substrate, and the parameters are as follows: In 0.67 Ga 0.33 As 5 nm, InP 50 nm, and a period of 10. When growing InGaAs and InP, the In source furnace temperature is unchanged. The growth rate ratio r 0.67 Ga 0.33 As and InP is r InGaAs : r InP =(1+ε InGaAs ) / 0.67=1.507. According to the value of r InGaAs 0.7 μm / h, r InP 0.4645 μm / h, the growth time of the adjustment structure In 0.67 Ga 0.33 As and InP is set to 25.7 s and 387.5 s, respectively. By adjusting the In source temperature and the Ga source temperature, the XRD characterization curve superlattice diffraction peak of the grown material is close to the InGaAs adjustment structure simulation curve superlattice diffraction peak, the 0-order diffraction peak deviation is less than 20 arc seconds, and the superlattice diffraction peak period deviation is less than 5%, thereby fixing the In source temperature and preliminarily determining the Ga source temperature. Figure 2The InGaAs calibration structure XRD simulation curve has two characteristic values, the 0th diffraction peak position and the superlattice period. The actual growth adjustment variables are two, the Ga source temperature and the InGaAs growth time. Therefore, this calibration result is unique.

[0029] (3) Growth of fully strain-compensated In 0.67 Ga 0.33 As / GaAs superlattice calibration structure, period 40, In 0.67 Ga 0.33 As 10 nm. When fully strain-compensated, the GaAs layer thickness d GaAs = -d InGaAs (ε InGaAs / ε GaAs ) = 2.62 nm. When growing In x Ga 1-x As and GaAs, the Ga source temperature is the same, so the growth rate of In x Ga 1-x As and GaAs is related, and their ratio is r InGaAs : r GaAs = a InGaAs : (1-x)a GaAs = (1+ε InGaAs ) / ((1+ε GaAs )(1-x)), when x is 0.67, r InGaAs : r GaAs = 3.176, so the growth time ratio of In 0.67 Ga 0.33 As and GaAs in the calibration structure is 1.200. By adjusting the Ga source temperature, the In x Ga 1-x As growth time (the corresponding GaAs growth time also changes), the XRD characterization curve of the grown material is consistent with the superlattice diffraction peak position of the calibration structure simulation curve. Thus, the Ga source temperature and the In 0.67 Ga 0.33 As growth rate are accurately obtained. Figure 3 The InGaAs calibration structure XRD simulation curve has two characteristic values, the 0th diffraction peak position and the superlattice period. The actual growth adjustment variables are two, the Ga source temperature and the InGaAs growth time. Therefore, this calibration result is unique.

[0030] (4) Growth of In 0.37 Al 0.63 As / InP superlattice calibration structure, parameters: In0.37 Al 0.63 As5nm, InP 50nm, period 10. In 0.37 Al 0.63 Growth rate ratio r of As and InP InAlAs : InP =(1+ε InAlAs ) / y=2.675. According to r InP =0.4645 μm / h, set the In 0.37 Al 0.63 Growth time of As and InP is 14.5 s, 387.5 s respectively. By adjusting the Al source temperature, the superlattice diffraction peak of the grown material XRD characterization curve is close to the InAlAs calibration structure simulation curve superlattice diffraction peak, the 0 order diffraction peak peak position deviation is less than 20 arc seconds, the superlattice diffraction peak peak position period deviation is less than 5%, thereby preliminarily determining the Al source temperature and In y Al 1-y Growth rate of As. Figure 4 is the InAlAs calibration structure XRD simulation curve, the simulation curve has two characteristic values, the 0 order diffraction peak peak position and the superlattice period. The actual growth adjustment variable is one, the Al source temperature. Therefore, this calibration result is unique. In addition, from the 0 order diffraction peak peak position in Figure 4 , the average mismatch degree of the calibration structure is -750 ppm, which is lower than 0.2%.

[0031] (5) Growth of completely strain-compensated In 0.37 Al 0.63 As / InAs superlattice calibration structure. Parameters: period 40, In 0.37 Al 0.63 As 10nm. InAs layer thickness d InAs =-d InAlAs (ε InAlAs / ε InAs )=3.16. In y Al 1-y As and InAs growth time ratio t InAlAs : AlAs =-ε InAs (1+ε InAs )y / (ε InAlAs (1+ε InAlAs ))=1.223. According to the parameters of the InAlAs calibration of the previous step, preliminarily calculate and set the Al source temperature and InAlAs growth time, InAs growth time. Then adjust the Al source temperature, In y Al 1-yAs growth time (the corresponding InAs growth time also changes), so that the XRD characterization curve of the grown material and the simulation curve of the calibration structure are consistent in the peak position of the superlattice diffraction peak. Thus, the Al source temperature and In y Al 1-y As growth rate. Figure 5 The XRD simulation curve of the InAlAs calibration structure has two characteristic values, the peak position of the 0-order diffraction peak and the superlattice period. The 0-order diffraction peak is basically coincident with the substrate peak S. The actual growth adjustment variables are two, the Al source temperature and the InAlAs growth time. Therefore, this calibration result is unique.

[0032] (6) According to the In source temperature, Ga source temperature, Al source temperature, InGaAs growth rate and InAlAs growth rate determined according to the above steps, as well as other growth parameters such as doping, set the growth program to grow the strain-compensated InGaAs / InAlAs quantum cascade laser material on the InP substrate.

[0033] The conventional growth method is as follows: first, grow In 0.53 Ga 0.47 As and In 0.52 Al 0.48 As monolayer, then grow In 0.53 Ga 0.47 As / In 0.52 Al 0.48 As superlattice, and each time only change the Ga source temperature or the Al source temperature, and gradually change the In 0.53 Ga 0.47 As / In 0.52 Al 0.48 As superlattice to the strain-compensated In 0.67 Ga 0.33 As / In 0.37 Al 0.63 As superlattice structure. And the changed component each time cannot be too large, otherwise the average mismatch degree is large, and lattice relaxation is easy to occur. Therefore, the structures to be debugged are far more than four. In addition, for the InGaAs / InAlAs superlattice, there are three variables, the Ga source temperature, the Al source temperature and the growth time, and the XRD characterization has only two characteristic values, so the characterization fitting result is not unique, and the error is large.

[0034] In summary, the application provides a strain compensation quantum cascade laser material growth method, which calibrates mismatched InGaAs, InAlAs material components and calculates material growth rate by growing four kinds of debugging and calibration structures, the average mismatch degree of the four kinds of material structures is greatly reduced, and the probability of lattice relaxation is very small. And the XRD characterization fitting result of each structure is unique. The epitaxial efficiency and accuracy of the finally grown strain compensation InGaAs / InAlAs quantum cascade laser material are improved.

[0035] Therefore, the present application effectively overcomes the shortcomings in the prior art and has high industrial utilization value.

Claims

1. A method of calibrating growth parameters for a strain-compensated quantum cascade laser material, comprising: The active region of the quantum cascade laser material is In x Ga 1-x As / In y Al 1-y As multi-quantum well, wherein 0.53 < x < 1, 0 < y < 0.52, by growing InGaAs tuning structure, InGaAs calibration structure, InAlAs tuning structure, InAlAs calibration structure, obtaining growth parameters In source temperature, Ga source temperature, Al source temperature, In x Ga 1-x As growth rate and In y Al 1-y As growth rate; wherein the InGaAs tuning structure is to grow In x Ga 1-x As / InP superlattice on InP substrate; The InGaAs calibration structure is: growing fully strain-compensated In x Ga 1-x As / GaAs superlattice with period 30~50, In x Ga 1-x As layer thickness d InGaAs =5~15 nm, GaAs layer thickness d GaAs =-d InGaAs (ε InGaAs / ε GaAs ), ε is the lattice mismatch degree; growing In x Ga 1-x As and GaAs with the same Ga source temperature, growth rate r InGaAs :r GaAs =(1+ε InGaAs ) / ((1+ε GaAs )(1-x)), r represents the growth rate, ε represents the mismatch degree, In x Ga 1-x As and GaAs growth time relationship is t InGaAs :t GaAs =ε GaAs (1+ε GaAs )(x-1) / (ε InGaAs (1+ε InGaAs )); by adjusting the Ga source temperature, In x Ga 1-x As growth time, the XRD characterization curve of the grown material and the superlattice diffraction peak of the calibration structure simulation curve are consistent, so as to accurately obtain the Ga source temperature and In x Ga 1-x As growth rate; The InAlAs tuning structure is grown on an InP substrate y Al 1-y As / InP superlattice The InAlAs calibration structure is a fully strain-compensated In y Al 1-y As / InAs superlattice, period 30~50, wherein In y Al 1-y As thickness d InAlAs is 5~15 nm, InAs layer thickness d InAs =-d InAlAs (ε InAlAs / ε InAs ), ε is the lattice mismatch degree; growth rate ratio r InAlAs :r InAs =(1+ε InAlAs ) / (y(1+ε InAs )), r represents the growth rate, and ε represents the mismatch degree; In y Al 1-y As and InAs growth time ratio t InAlAs :t AlAs =-ε InAs (1+ε InAs )y / (ε InAlAs (1+ε InAlAs )), by adjusting the Al source temperature, In y Al 1-y As growth time, the XRD characterization curve of the grown material and the InAlAs calibration structure simulation curve superlattice diffraction peak peak position are consistent, so that the Al source temperature and In y Al 1-y As growth rate are accurately obtained.

2. The method of claim 1, wherein, The InGaAs adjusting structure is: growing In x Ga 1-x As / InP superlattice on InP substrate, wherein In x Ga 1-x As is 2-6 nm, InP is 40-60 nm, the period is 10-20, and In x Ga 1-x As and InP is grown at the same In source temperature, In x Ga 1-x As and InP is grown at the growth rate ratio (1+ε InGaAs ) / x, ε represents the lattice mismatch degree, and then the growth rate r InGaAs is taken as 0.4-1 μm / h, the growth time of the adjusting structure InP and In x Ga 1-x As is set, the In source temperature and the Ga source temperature are adjusted, the superlattice diffraction peak peak position of the XRD characterization curve of the grown material is close to the superlattice diffraction peak peak position of the InGaAs adjusting structure simulation curve, the 0-order diffraction peak peak position deviation is less than 20 arc seconds, the superlattice diffraction peak peak position period deviation is less than 5%, so that the In source temperature is fixed, the Ga source temperature is preliminarily determined, and the InP growth rate is obtained.

3. The method of claim 1, wherein, The InAlAs adjusting structure is: growing In y Al 1-y As / InP superlattice, In y Al 1-y As 2~6 nm, InP 40~60 nm, period 10~20, growth rate r InAlAs :r InP =(1+ε InAlAs ) / y, ε represents the lattice mismatch degree, and then according to the obtained InP growth rate, the growth time of each layer of the InAlAs adjusting structure is set, the Al source temperature is adjusted, the superlattice diffraction peak of the XRD characterization curve of the grown material is close to the superlattice diffraction peak of the simulation curve of the InAlAs adjusting structure, the peak position deviation of the 0-order diffraction peak is less than 20 arc seconds, and the peak position period deviation of the superlattice diffraction peak is less than 5%, so that the Al source temperature is preliminarily determined.

4. The method of claim 1, wherein, first InGaAs tuning structure, InGaAs calibration structure, then InAlAs tuning structure, InAlAs calibration structure, or first InAlAs tuning structure, InAlAs calibration structure, then InGaAs tuning structure, InGaAs calibration structure.

5. A strain-compensated quantum cascade laser material, characterized in that, The strain-compensated quantum cascade laser material is grown on an InP substrate by setting a growth program containing the growth parameters defined in claim 1.

6. Use of the strain-compensated quantum cascade laser material of claim 5 in developing a laser to emit a mid-infrared waveband laser.

7. Use of the strain-compensated quantum cascade laser material of claim 5 in gas detection or infrared countermeasures.

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