Design And Simulation Of AlGaN/GaN HEMT With Barrier Surface P-Type Doped For High Energy-Efficiency

AlGaN/GaN HEMT（High Electron Mobility Transistor）has the advantages of high breakdown voltage,high work frequency and high output power.It is widely used in consumer electronics,national defence technology,industrial control and other fields.At present,the research of AlGaN/GaN HEMT mainly focuses on the improvement of traditional parameters of devices such as breakdown voltage.Under the development concept of a new era of energy conservation,emission reduction,green and high efficiency,it is of great practical significance to combine the traditional AC/DC parameters with the power-added efficiency,and design the energy-efficiency characteristics from the internal structure level to meet the needs of high energy-efficiency semiconductor devices.In this thesis,the principles and methods of high energy-efficiency design of AlGaN/GaN HEMT are discussed based on the device structure design and aiming at improving the energy-efficiency characteristics.Firstly,in this thesis,by the control variable method and EE＿HEMT1 model in ADS software,the influence mechanism of key performance parameters in AlGaN/GaN HEMT on the energy-efficiency characteristics of the device is qualitatively simulated and analyzed.The simulation results show that by reducing the absolute value of the threshold voltage,increasing the transconductance,increasing the breakdown voltage,and reducing the parasitic resistance and capacitance,the power-added efficiency of the device can be effectively improved,which is conducive to the high-power and high-efficiency application.At the same time,it is found in the simulation that the gate-source capacitance has the most significant impact on the power-added efficiency of the device,which becomes an important starting point for the design of high energy-efficiency devices.Secondly,a PDBS-HEMT（P-type Doped Barrier Surface HEMT）with a double P-type doped region on the barrier layer surface is proposed.By the design of a P-type doped region on the barrier layer surface between gate-source and gate-drain,the internal electric field and the distribution of the depletion layer are modulated.The simulation analysis of AC/DC parameters shows that the doped region between the gate and drain optimizes the peak value of the electric field at the corner of the gate,reduces the electric field crowding effect,increases the breakdown voltage by 35.9%,and the breakdown voltage of the device can be further enhanced with the increase of the doping concentration and thickness of the doping region;the doped region suppresses the extension of the depletion region to both sides of the gate,increases the vertical distance between the gate and the lower surface of the depletion layer,and reduces the gate-source capacitance and gate-drain capacitance by 14.6%and 14.3%respectively;the improvement of parasitic capacitance optimizes the frequency characteristics of the device,the maximum oscillation frequency of the PDBS-HEMT is increased by 10.5%.At the same time,the variation of output power and power-added efficiency of the PDBS-HEMT with input power under different work frequencies and amplification conditions are studied.The simulation results show that when V_gs=-4 V,V_ds=20 V,the saturated output power density at 600 MHz and 1200 MHz is 10.9 W/mm and 9.3W/mm,the maximum power-added efficiency is 85.5%and 88.4%,and the saturated power gain is 11.4 d B and 10.7 d B;when the frequency is increased to 2400 MHz,the saturated output power density is 6.4 W/mm,the maximum power-added efficiency is 79%,and the saturated power gain is 9.1 d B.When the frequency is 1200 MHz,V_ds=20 V,the device work at the class B amplification state achieves the maximum power-added efficiency of72.6%and has better output linearity.In the simulation range,PDBS-HEMT has better energy-efficiency output capability than traditional structures,and gives full play to the advantage of low parasitic capacitance.Finally,a PMRB-HEMT（P-type Layer and Multi Recessed Buffer HEMT）with a P-type layer on the barrier layer surface and a multi-recessed buffer layer is proposed.The simulation analysis of AC/DC parameters shows that the increase of average barrier layer thickness improves the saturated drain current and transconductance of the device,prolongs the length of the transconductance saturation region,and enhances the ability of gate control;the P-type layer and the recessed buffer layer affect the peak electric field at the gate of drain side,and the breakdown voltage is increased by 52.3%;by optimizes the distribution of depletion region,the gate-source capacitance and gate-drain capacitance are reduced by 15.7%and 17.8%respectively;the cut-off frequency and maximum oscillation frequency were increased by 9.7%and 15.6%respectively.In addition,in the simulation process,the power-added efficiency of the device increases first and then decreases with the increase of work frequency.Under the conditions of frequency 1200 MHz,V_ds=20 V and class B amplification status,the power-added efficiency achieves an optimal value of 75.8%.By comparing the normalized power-added efficiency of PDBS-HEMT,PMRB-HEMT and various device structures,shows that the two new structures proposed in this thesis show good energy-efficiency characteristics and have great advantages and potential in high energy-efficiency applications.The work of this thesis shows that it is effective way to improve the energy-efficiency characteristics of AlGaN/GaN HEMT through study and summarize the deep influence mechanism of energy-efficiency characteristics from the internal structure of the device,and design the device structure,which provides a theoretical basis and design method for the further research of high energy-efficiency RF power amplifier.