CN102592999B - Method for optimizing thickness of channel layer of quantum well high electron mobility transistor (HEMT) appliance - Google Patents

Abstract

The invention discloses a method for optimizing the thickness of a channel layer of an AlN/GaN/AlN quantum well high electron mobility transistor (HEMT) appliance. Appliance simulation shows that the performance of the appliance can be well improved by controlling the thickness of a GaN channel to be between 15 and 22nm in a material growing process, the AlN/GaN/AlN quantum well HEMT appliance is manufactured according to the obtained result, and basis for optimizing the AlN/GaN/AlN quantum well HEMT appliance is provided. The method has great significance for improving the performance of the appliance and optimizing the design of the appliance.

Description

A kind of method of optimizing quantum well HEMT device channel layer thickness

Technical field

The present invention relates to electronic component technology, specifically refer to a kind of method of the AlN/GaN/AlN of optimization quantum well HEMT device channel layer thickness.

Background technology

Owing to having extensive use at aspects such as high-power, high frequency and high-temperature amplifiers, AlGaN/GaN heterojunction High Electron Mobility Transistor (HEMT) becomes the focus of semiconductor applications research in the past in the more than ten years.But along with the dwindling of device size, the series of problems such as current collapse, self-heating effect, leakage current and short-channel effect have seriously restricted further developing of device.More high-power for HEMT device is had, reduce current collapse effect people simultaneously and proposed some variants based on AlGaN/GaN structure, such as: the people such as the W.Lanfort of the New York State University in 2004 have proposed AlGaN/InGaN/GaN heterostructure; The people such as the O.Katz of engineering institute of Israel in 2005 have proposed InAlN/GaN heterostructure, and they have proved that respectively the HEMT device of these two kinds of structure fabrications has larger power by experiment; The people such as the J.Kuzmik of Technical University of Vienna in 2008 are inserted into AlN thin layer in the InAlN/GaN heterojunction of Lattice Matching, result proves that this structure has not only reduced Alloy disorder scattering but also increased the binding force of two-dimensional electron gas in raceway groove, thereby has greatly improved device performance; The people such as the Dabrian of the SVT Associates of top MBE device fabrication company of the world in 2008 have reported that AlN/GaN/AlN quantum well HEMT has very high electron mobility (> 1800cm²/ Vs) and two-dimensional electron gas density (> 3 × 10³cm^-2).

In these new devices that are derived based on AlGaN/GaN HEMT, AlN/GaN/AlN quantum well HEMT is undoubtedly very promising one.This is because AlN/GaN heterojunction, except having very strong polarity effect, also has larger conduction band band rank, can suppress short-channel effect and reduce threshold voltage.Due to these good characteristics, AlN/GaN/AlN quantum well HEMT, except having important application in the device of high transconductance, low threshold voltage, can also be applied to all many-sides such as high-power transparent organism transducer, Terahertz plasma wave launcher.But under high frequency condition, due to phon scattering, the electronics with high kinetic energy is easy to overflow drain and is captured by trap, thereby causes current collapse effect.In order to suppress current collapse effect, the raceway groove of AlN/GaN/AlN quantum well HEM must possess high conduction band barrier and high two-dimensional electron gas density simultaneously.Along with reducing of GaN channel layer thickness, raceway groove place conduction band barrier height monotone increasing, but because the negative polarization charge of GaN channel layer and AlN resilient coating interface has depletion action to two-dimensional electron gas, reducing GaN channel layer thickness will cause the reduction of two-dimensional electron gas density.

Therefore in order to guarantee the high conduction band barrier in raceway groove place and high two-dimensional electron gas density simultaneously, the device architecture of optimizing AlN/GaN/AlN quantum well HEMT seems particularly important.The present invention sets about research from the GaN channel layer thickness of AlN/GaN/AlN quantum well HEMT, investigates the impact of channel layer thickness on conduction band barrier height and two-dimensional electron gas density, and the result drawing will have certain directive significance to the development of new device.

Summary of the invention

The invention provides a kind of method of the AlN/GaN/AlN of optimization quantum well HEMT device channel layer thickness, the method obtains conduction band barrier height and the two-dimensional electron gas density rule with channel layer varied in thickness by numerical simulation.In order to make raceway groove obtain high conduction band barrier and high two-dimensional electron gas density simultaneously, we define the common logarithm of two-dimensional electron gas density and the product of conduction band barrier height is raceway groove figure of merit, obtain best channel layer thickness by analyzing raceway groove figure of merit with the curve of channel layer varied in thickness, and then made AlN/GaN/AlN quantum well HEMT device according to the structural design after optimizing.Its step is as follows:

1. first build the structural model of AlN/GaN/AlN quantum well HEMT device, in AlN single crystalline substrate, form successively AlN resilient coating, GaN channel layer, AlN barrier layer and Al₂o₃gate dielectric layer, then formation source, drain electrode on AlN barrier layer, and at Al₂o₃on gate dielectric layer, form gate electrode;

2. make three experiment measuring samples, sample 1: the thick AlN film of 1 μ m of growing in the thick AlN single crystalline substrate of 500 μ m; Sample 2: the thick GaN film of 50nm of growing in the thick AlN single crystalline substrate of 500 μ m; Sample 3: 1um thick AlN resilient coating, 50nm thick GaN channel layer, 3.5nm thick AlN barrier layer and the thick Al of 5nm grow successively in the thick AlN single crystalline substrate of 500 μ m₂o₃gate dielectric layer;

3. inmeasuring process 2, gainedsample 1 obtains the performance parameter of AlN: energy gap is 6.2eV, electron effective mass m_e=0.3m₀, electron mobility is 300～500cm²/ Vs, relative dielectric constant ε_r=8.5, effectively conduction band states density is N_c=4.1 × 10¹⁸, electron lifetime is about 10^-9s, electron saturation velocities v_sat=4.8 × 10⁶cm/s; Measure the performance parameter thatsample 2 obtains GaN: energy gap is 3.47eV, electron effective mass m_e=0.222m₀, electron mobility is 1300～1500cm²/ Vs, relative dielectric constant ε_r=9.5, effectively conduction band states density is N_c=2.65 × 10¹⁸, electron lifetime is about 10^-8s, electron saturation velocities v_sat=1.03 × 10⁷cm/s; Measuringsample 3 by capacitance voltage method obtains: Al₂o₃the polarization charge densities of gate dielectric layer and AlN barrier layer interface is-1.6 × 10¹³cm^-2, the polarization charge densities of AlN barrier layer and GaN channel layer interface is 2.6 × 10¹³cm^-2, the polarization charge densities of GaN channel layer and AlN resilient coating interface is-2.6 × 10¹³cm^-2;

4. build physical model: the fundamental equation of Numerical Simulation of A Semiconductor Device is the equation of current density in continuity equation, electronics and the hole in Poisson's equation, electronics and hole, charge carrier is compound adds continuity equation by producing compound term, comprise that SRH is compound, Auger is compound and radiation recombination, also to consider thermal effect, the speed saturation effect of charge carrier simultaneously, solve with Finite Element Method discretization simultaneous iteration, the tunneling effect of potential barrier is independent equation, with above-mentioned equation self-consistent solution;

5. according to the experimental measurements ofstep 2, physical parameter is set, making simulated environment temperature is 300K, and fixing channel layer thickness obtains respectively by numerical simulation the curve that conduction band barrier height and two-dimensional electron gas density change with lengthwise position;

6. change channel layer thickness, repeatingstep 5, obtains respectively a series of curves that under different channel layer thickness, conduction band barrier height and two-dimensional electron gas density change with lengthwise position;

7. in a series of curves that under the different channel layer thickness that obtain in step 6, conduction band barrier height changes with lengthwise position, choose a fixed position, such as channel layer middle distance AlN barrier layer and 5nm place, GaN channel layer interface, obtain the conduction band barrier height Ec of this position with the curve of channel layer varied in thickness;

8. in a series of curves that under the different channel layer thickness that obtain, two-dimensional electron gas density changes with lengthwise position, choose two-dimensional electron gas density peak value as research object in step 6, obtain the curve of two-dimensional electron gas density peak value ns with channel layer varied in thickness;

9. definition n_scommon logarithm Log (n_s) and E_cproduct, i.e. E_clog (n_s) be raceway groove figure of merit, two curves that utilize step 7 and step 8 to obtain, obtain the curve of raceway groove figure of merit with channel layer varied in thickness;

10. observe the curve of raceway groove figure of merit with channel layer varied in thickness, find that working as channel layer thickness is that between 15～22nm, raceway groove figure of merit has maximum, illustrate channel layer THICKNESS CONTROL between 15～22nm, device channel can have the character of high conduction band barrier and high two-dimensional electron gas density concurrently, thereby can suppress well current collapse effect and improve device performance;

11. prepare AlN/GaN/AlN quantum well HEMT device according to the result of simulation, first, in AlN single crystalline substrate, utilize metal organic chemical vapor deposition technique growing AIN resilient coating, GaN channel layer and AlN barrier layer successively;

12. on AlN barrier layer, utilizes atom layer deposition process deposit Al₂o₃gate dielectric layer, then by photoetching process in source, drain region forms etching required window, adopts reactive ion etching process to remove the Al of source, drain region₂o₃dielectric film;

13. utilize photoetching process to obtain source, drain region window, then adopt electron beam evaporation process, on source, drain region window, evaporate metal ohmic contact Ti/Al/Ni/Au, form source electrode and drain electrode, finally at Al₂o₃on gate dielectric layer, utilize photoetching process to obtain area of grid window, and on this area of grid window, adopt electron beam evaporation process evaporation gate metal Ni/Au, form grid.

Advantage of the present invention is: considered conduction band barrier height and the two-dimensional electron gas density rule with channel layer varied in thickness simultaneously, can determine best channel layer thickness, make electron channel possess high conduction band barrier and high two-dimensional electron gas density simultaneously, thereby provide scheme targetedly for suppressing current collapse effect and improving device performance.

Accompanying drawing explanation

Fig. 1 is the structural representation of AlN/GaN/AlN quantum well HEMT device.

Fig. 2 is longitudinal distribution map of conduction band barrier height under different channel layer thickness.

Fig. 3 is longitudinal distribution map of two-dimensional electron gas density under different channel layer thickness.

Fig. 4 is that (right side) lengthwise position coordinate is that the conduction band barrier height at 5nm place is with the curve of channel layer varied in thickness; (left side) two-dimensional electron gas density peak value is with the curve of channel layer varied in thickness.

Fig. 5 is raceway groove figure of merit E_clog (n_s) with the curve of channel layer varied in thickness.

Embodiment

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is elaborated:

1. build the structural model of AlN/GaN/AlN quantum well HEMT device, as shown in Figure 1, in the thick AlN single crystalline substrate of 500 μ m, form successively thick AlN barrier layer and the thick Al of 5nm of AlN resilient coating, the GaN channel layer of variable thickness, 3.5nm that 1 μ m is thick₂o₃gate dielectric layer, then formation source, drain electrode on AlN barrier layer, and at Al₂o₃on gate dielectric layer, form gate electrode, the length of source, leakage and gate electrode is 1 μ m, and total device length is 5 μ m;

2. make three experiment measuring samples, sample 1: the thick AlN film of 1 μ m of growing in the thick AlN single crystalline substrate of 500 μ m; Sample 2: the thick GaN film of 50nm of growing in the thick AlN single crystalline substrate of 500 μ m; Sample 3: 1 μ m thick AlN resilient coating, 50nm thick GaN channel layer, 3.5nm thick AlN barrier layer and the thick Al of 5nm grow successively in the thick AlN single crystalline substrate of 500 μ m₂o₃gate dielectric layer;

3. inmeasuring process 2, gainedsample 1 obtains the performance parameter of AlN: energy gap is 6.2eV, electron effective mass m_e=0.3m₀, electron mobility is 300～500cm²/ Vs, relative dielectric constant ε_r=8.5, effectively conduction band states density is N_c=4.1 × 10¹⁸, electron lifetime is about 10^-9s, electron saturation velocities v_sat=4.8 × 10⁶cm/s; Measure the performance parameter thatsample 2 obtains GaN: energy gap is 3.47eV, electron effective mass m_e=0.222m₀, electron mobility is 1300～1500cm²/ Vs, relative dielectric constant ε_r=9.5, effectively conduction band states density is N_c=2.65 × 10¹⁸, electron lifetime is about 10^-8s, electron saturation velocities v_sat=1.03 × 10⁷cm/s; Measuringsample 3 by capacitance voltage method obtains: Al₂o₃the polarization charge densities of gate dielectric layer and AlN barrier layer interface is-1.6 × 10¹³cm^-2, the polarization charge densities of AlN barrier layer and GaN channel layer interface is 2.6 × 10¹³cm^-2, the polarization charge densities of GaN channel layer and AlN resilient coating interface is-2.6 × 10¹³cm^-2;

4. build physical model: the fundamental equation of Numerical Simulation of A Semiconductor Device is the equation of current density in continuity equation, electronics and the hole in Poisson's equation, electronics and hole, charge carrier is compound adds continuity equation by producing compound term, comprise that SRH is compound, Auger is compound and radiation recombination, also to consider thermal effect, the speed saturation effect of charge carrier simultaneously, solve with Finite Element Method discretization simultaneous iteration, the tunneling effect of potential barrier is independent equation, with above-mentioned equation self-consistent solution;

5. according to the experimental measurements ofstep 2, physical parameter is set, making simulated environment temperature is 300K, and fixing channel layer thickness obtains respectively by numerical simulation the curve that conduction band barrier height and two-dimensional electron gas density change with lengthwise position;

6. change channel layer thickness, repeatingstep 5, obtains respectively under different channel layer thickness conduction band barrier height (Fig. 2) and two-dimensional electron gas density (Fig. 3) with a series of curves of lengthwise position variation.As can be seen from Figure 2, along with channel layer thickness reduces, channel barrier height monotone increasing, raceway groove strengthens the constraint ability of electronics.As can be seen from Figure 3, two-dimensional electron gas density reduce with channel layer thickness and dullness reduce, this is that in the time that channel layer thickness reduces, negative polarization electric charge produces depletion action to two-dimensional electron gas because of GaN channel layer and the AlN resilient coating interface polarization charge negative because polarity effect has;

7. in a series of curves that under the different channel layer thickness that obtain, conduction band barrier height changes with lengthwise position, choose a fixed position (lengthwise position coordinate is 5nm) in step 6, obtain the conduction band barrier height E of this position_cwith the curve (Fig. 4 right side) of channel layer varied in thickness, from figure, can see intuitively that conduction band barrier height reduces with channel layer thickness and monotone increasing;

8. in a series of curves that under the different channel layer thickness that obtain, two-dimensional electron gas density changes with lengthwise position, choose two-dimensional electron gas density peak value as research object in step 6, obtain two-dimensional electron gas density peak value n_swith the curve (Fig. 4 left side) of channel layer varied in thickness, from figure, can see intuitively that two-dimensional electron gas density reduces with channel layer thickness and dullness reduces;

9. definition n_scommon logarithm Log (n_s) and E_cproduct, i.e. E_clog (n_s) be raceway groove figure of merit, two curves that utilize step 7 and step 8 to obtain, obtain the curve (Fig. 5) of raceway groove figure of merit with channel layer varied in thickness, find that from Fig. 5 working as channel layer thickness is that between 15～22nm, raceway groove figure of merit has maximum, illustrate that by channel layer THICKNESS CONTROL device has optimum performance between 15～22nm;

10. prepare AlN/GaN/AlN quantum well HEMT device according to the result of simulation, first AlN single crystalline substrate thick 500 μ m is placed in to the reative cell of metal organic chemical vapor deposition (MOCVD) equipment, the vacuum degree of reative cell is evacuated to 1 × 10^-2under Torr, at the mixed gas protected lower of hydrogen and ammonia, AlN substrate is carried out to high-temperature heat treatment, heating-up temperature is 1100 ℃, and be 5min heating time, and chamber pressure is 40Torr, and passing into hydrogen flowing quantity is 1500sccm, and ammonia flow is 1500sccm;

Underlayer temperature is reduced to 1080 ℃ by 11., and maintenance growth pressure is 40Torr, and hydrogen flowing quantity is 1500sccm, and ammonia flow is 1500sccm, in reative cell, passes into the aluminium source that flow is 30 μ mol/min, and epitaxial growth thickness is the AlN resilient coating of 1 μ m;

Growth temperature is reduced to 800 ℃ by 12., and maintenance growth pressure is 40Torr, and hydrogen flowing quantity is 1500sccm, and ammonia flow is 1500sccm, in reative cell, passes into the gallium source that flow is 50 μ mol/min, the GaN channel layer take growth thickness as 18.5nm;

13. pass into He Jia source, aluminium source in reative cell simultaneously, and maintaining reaction temperature is 800 ℃, control flow well, the AlN barrier layer that growth thickness is 3.5nm, and pass into gallium source is in order to increase aluminium atom in surperficial diffusivity simultaneously;

14. form Al₂o₃gate dielectric layer: adopt ALD technique depositing Al at 300 ℃₂o₃film, the 60s that then anneals in oxygen atmosphere at 600 ℃, the Al that acquisition thickness is 5nm₂o₃layer, then to sample surfaces positive-glue removing, rotating speed is 5000 turn/min, then dries 10min in temperature is the baking oven of 80 ℃, by photoetching and be developed in source, drain region and form the required window of etching, adopt reactive ion etching process to remove the Al of source, drain region₂o₃dielectric film;

15. photolithographic source, drain region: for better stripping metal, first on sample, get rid of binder, rotating speed is 8000 turn/min, time is 30s, in temperature is the high temperature oven of 160 ℃, dry 20min, and then on this sample positive-glue removing, rotating speed is 5000 turn/min, finally in temperature is the high temperature oven of 80 ℃, dry 10min, photoetching obtains length and is source, the drain region window of 1 μ m;

16. evaporation sources, leakage metal: adopt tetra-layers of metal of electron beam evaporation process deposit Ti/Al/Ni/Au;

17. peel off source, leakage metal and annealing: after soaking more than 20min, carry out ultrasonic processing in acetone, then dry up with nitrogen.Sample is put into quick anneal oven anneals: first pass into nitrogen about 7 minutes to annealing furnace, then, under nitrogen atmosphere, temperature is to carry out 30s short annealing under 800 ℃ of conditions;

18. photoetched grid regional windows: get rid of binder on sample, rotating speed is 8000 turn/min, and the time is 30s; In being the high temperature oven of 160 ℃, temperature dries 20min; And then on this sample positive-glue removing, rotating speed is 5000 turn/min, finally in temperature is the baking oven of 80 ℃, dries 10min, it is the area of grid window of 1 μ m that photoetching obtains length;

19. evaporation gate metals: adopt electron beam evaporation process deposition Ni/Au double layer of metal, subsequently sample is immersed in stripper to 2 minutes, form grid.So far completed the making of the AlN/GaN/AlN quantum well HEMT device after optimizing.

Claims (1)

Translated fromChinese

1.一种优化量子阱HEMT器件沟道层厚度的方法，其特征在于包括以下步骤：1. a method for optimizing the channel layer thickness of quantum well HEMT device, is characterized in that comprising the following steps:1）首先构建AlN/GaN/AlN量子阱HEMT器件的结构模型，即在AlN单晶衬底上依次形成AlN缓冲层、GaN沟道层、AlN势垒层和Al₂O₃栅介质层，然后在AlN势垒层上形成源、漏电极，以及在Al₂O₃栅介质层上形成栅电极；1) First construct the structural model of the AlN/GaN/AlN quantum well HEMT device, that is, sequentially form the AlN buffer layer, GaN channel layer, AlN barrier layer and Al₂ O₃ gate dielectric layer on the AlN single crystal substrate, and then Forming source and drain electrodes on the AlN barrier layer, and forming a gate electrode on the_Al2O3 gate dielectric layer_;2）制作三个实验测量样品，样品1：在500μm厚的AlN单晶衬底上生长1μm厚的AlN薄膜；样品2：在500μm厚的AlN单晶衬底上生长50nm厚的GaN薄膜；样品3：在500μm厚的AlN单晶衬底上依次生长1μm厚的AlN缓冲层、50nm厚的GaN沟道层、3.5nm厚的AlN势垒层和5nm厚的Al₂O₃栅介质层；2) Make three experimental measurement samples, sample 1: grow a 1 μm thick AlN film on a 500 μm thick AlN single crystal substrate; sample 2: grow a 50nm thick GaN film on a 500 μm thick AlN single crystal substrate; sample 3: A 1 μm thick AlN buffer layer, a 50nm thick GaN channel layer, a 3.5nm thick AlN barrier layer and a 5nm thick Al₂ O₃ gate dielectric layer are sequentially grown on a 500 μm thick AlN single crystal substrate;3）测量步骤2）中所得样品1得到AlN的性能参数：禁带宽度为6.2eV，电子有效质量m_e=0.3m₀，电子迁移率为300～500cm²/Vs，相对介电常数ε_r=8.5，有效导带态密度为N_c=4.1×10¹⁸，电子寿命约为10^-9s，电子饱和速度v_sat=4.8×10⁶cm/s；测量样品2得到GaN的性能参数：禁带宽度为3.47eV，电子有效质量m_e=0.222m₀，电子迁移率为1300～1500cm²/Vs，相对介电常数ε_r=9.5，有效导带态密度为N_c=2.65×10¹⁸，电子寿命约为10^-8s，电子饱和速度v_sat=1.03×10⁷cm/s；用电容电压法测量样品3得到：Al₂O₃栅介质层与AlN势垒层界面处的极化电荷密度为-1.6×10¹³cm^-2，AlN势垒层与GaN沟道层界面处的极化电荷密度为2.6×10¹³cm^-2，GaN沟道层与AlN缓冲层界面处的极化电荷密度为-2.6×10¹³cm^-2；3) Measure the performance parameters of AlN obtained from sample 1 obtained in step 2): the bandgap width is 6.2eV, the electron effective mass m_e =0.3m₀ , the electron mobility is 300-500cm² /Vs, and the relative permittivity ε_r =8.5, the effective conduction band density of states is N_c =4.1×10¹⁸ , the electron lifetime is about 10^-9 s, and the electron saturation velocity v_sat =4.8×10⁶ cm/s; the performance parameters of GaN obtained by measuring sample 2 are: forbidden The band width is 3.47eV, the electron effective mass m_e =0.222m₀ , the electron mobility is 1300～1500cm² /Vs, the relative permittivity ε_r =9.5, the effective conduction band state density is N_c =2.65×10¹⁸ , The electron lifetime is about 10^-8 s, and the electron saturation velocity v_sat =1.03×10⁷ cm/s; the sample 3 is measured by the capacitive voltage method: the polarization charge at the interface between the Al₂ O₃ gate dielectric layer and the AlN barrier layer The density is -1.6×10¹³ cm^-2 , the polarized charge density at the interface between the AlN barrier layer and the GaN channel layer is 2.6×10¹³ cm^-2 , the polarized charge density at the interface between the GaN channel layer and the AlN buffer layer The density is -2.6×10¹³ cm^-2 ;4）构建物理模型：半导体器件数值模拟的基本方程是泊松方程、电子与空穴的连续性方程、电子与空穴的电流密度方程，载流子复合通过产生复合项加入连续性方程，包括SRH复合、Auger复合和辐射复合，同时还要考虑到载流子的热效应、速度饱和效应，用有限元方法离散化联立迭代求解，势垒的隧穿效应为独立方程，与上述方程自洽求解；4) Building a physical model: The basic equations for numerical simulation of semiconductor devices are the Poisson equation, the continuity equation of electrons and holes, and the current density equation of electrons and holes. Carrier recombination is added to the continuity equation by generating composite terms, including SRH recombination, Auger recombination, and radiative recombination, while taking into account the thermal effect and velocity saturation effect of carriers, use the finite element method to discretize simultaneous iterative solutions. The tunneling effect of the potential barrier is an independent equation, which is self-consistent with the above equation solve;5）根据步骤2）的实验测量结果设置物理参数，使模拟环境温度为300K，固定沟道层厚度，由数值模拟分别得到导带势垒高度和二维电子气密度随纵向位置变化的曲线；5) Set the physical parameters according to the experimental measurement results in step 2), so that the simulated ambient temperature is 300K, the thickness of the channel layer is fixed, and the curves of the conduction band barrier height and the two-dimensional electron gas density changing with the longitudinal position are respectively obtained by numerical simulation;6）改变沟道层厚度，重复步骤5），分别得到不同沟道层厚度下导带势垒高度和二维电子气密度随纵向位置变化的一系列曲线；6) Change the thickness of the channel layer, repeat step 5), and obtain a series of curves of the conduction band barrier height and the two-dimensional electron gas density with the longitudinal position under different channel layer thicknesses;7）在步骤6）中得到的不同沟道层厚度下导带势垒高度随纵向位置变化的一系列曲线中，选取一个固定位置，沟道层中距离AlN势垒层和GaN沟道层界面5nm处，得到该位置处的导带势垒高度E_c随沟道层厚度变化的曲线；7) In the series of curves obtained in step 6) of the conduction band barrier height varying with the longitudinal position under different channel layer thicknesses, select a fixed position, the distance between the channel layer and the interface between the AlN barrier layer and the GaN channel layer At 5nm, obtain the curve of the conduction band barrier height_Ec varying with the thickness of the channel layer at this position;8）在步骤6）中得到的不同沟道层厚度下二维电子气密度随纵向位置变化的一系列曲线中，选取二维电子气密度峰值作为研究对象，得到二维电子气密度峰值n_s随沟道层厚度变化的曲线；8) In the series of curves of the two-dimensional electron gas density changing with the longitudinal position at different channel layer thicknesses obtained in step 6), the peak value of the two-dimensional electron gas density is selected as the research object, and the peak value of the two-dimensional electron gas density n_s is obtained Curves varying with channel layer thickness;9）定义n_s的常用对数Log(n_s)与E_c的乘积，即E_c Log(n_s)为沟道优值因子，利用步骤7和步骤8得到的两条曲线，得到沟道优值因子随沟道层厚度变化的曲线；9) Define the product of the common logarithm Log(n_s ) of n_s and E_c , that is, E_c Log(n_s ) is the channel figure of merit, and use the two curves obtained in steps 7 and 8 to obtain the channel The curve of figure of merit varying with the thickness of the channel layer;10）观察沟道优值因子随沟道层厚度变化的曲线，以沟道优值因子具有最大值来确定沟道层最佳厚度。10) Observe the curve of the channel figure of merit changing with the channel layer thickness, and determine the optimal thickness of the channel layer with the channel figure of merit having the maximum value.

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