Physical-based Statistical Model For Microwave GaN HEMTs

Gallium Nitride（GaN）high electron-mobility transistors（HEMTs）have been promising devices duo to high frequency,high power and high efficiency applications.As a result,it is essential to establish an accurate model for GaN HEMT for the efficiency of circuit design.Up to now,many research works on GaN HEMTs modeling have been done based on physics and equivalent circuit.However,empirical or physical model inevitably depends on too many fitting parameters,causing multi-value effect,which hinders the extraction of parameters.Moreover,factors which affect the device’s consistency such as,variations of process line,model applicability and environment,pose great challenges to the optimization of process and circuit design.Therefore,the physical-based statistical model for GaN HEMT is urgent to relate the microwave characteristics to physical parameters of the device in the process of circuit design and process line monitoring.The main researches in this paper are presented as follows.1.Research on small signal equivalent circuit model for GaN HEMT.In order to establish small signal equivalent circuit model for GaN HEMT,S parameters of GaN HEMT are measured.Then the extrinsic and intrinsic elements are extracted respectively under cold and hot statuses,followed by the modeling of small signal equivalent circuit model based on 19 elements.2.Research on physical model for GaN HEMT based on surface potential.In order to establish the physical model for GaN HEMT based on surface potential,thirty GaN HEMTs from 10 batches are measured,including DC I-V and large signal properties(output powerP_out,power added efficiency PAE,etc).Based on the small signal equivalent circuit model,the nonlinear drain-source currentI_ds model and nonlinear gate capacitance(C_{g s}andC_gd)models based on surface potential have been established.In order to efficiently obtain fitting parameters from physical model,two devices selected from 10 batches are modeled simultaneously,extracting reasonable empirical parameters according to device fluctuation.Then the precise physical model has been established eventually,and its accuracy and application have been verified by comparing measured and simulatedP_{ou t},PAE andG_ain.3.Research on physically statistical model for Ga N HEMT.In order to establish physically statistical model of GaN HEMT,a sample with 30GaN HEMT has been modeled based on surface potential.Then the statistical characteristics of all physical parameters from the model have been obtained,using a series of statistical processes such as principle component analysis,factor analysis model,multiple regression algorithm and Monte Carlo simulation.Thus physically large signal statistical model of GaN HEMT has been established.The results show that good agreements have been achieved by comparing measured and simulated distributions,averages and standard deviations ofP_out and PAE,which validates the model accurately.