Study And Modeling On The High Temperature Characteristics Of GaN HEMT Devices

Compared with the traditional Si and GaAs materials,the gallium nitride(GaN)high electron mobility transistors(HEMTs)become increasingly available and prove themselves as promising candidates for high temperature,high frequency and high power applications,due to their excellent physical properties of wide band gap,high critical breakdown field,high electron mobility and so forth.To make full use of these superior properties of GaN HEMT devices,accuracy device models of GaN HEMTs are expected to facilitate the computer aided circuit design and simulation.GaN HEMTs differ from the traditional power devices in channel formation,current density,structure and conductivity,therefore it is difficult to describe and predict the ?-?characteristics,frequency characteristics and power characteristics by using traditional models developed for Si and GaAs devices.It is necessary to establish an accurate model to describe the electrical characteristics of GaN HEMT devices,according to the special structure characteristics of the device itself.The main work of this article is as follows:First,select the appropriate topology of the equivalent circuit and extract the parasitic parameters of the small signal model.This method is simple and accurate,and it can also avoid a lot of computation.The description of the nonlinear characteristics is the critical factor in modeling.Based on the analysis on the traditional ?-? model,we selected the appropriate mathematical formula to describe the relationship between drain current and gate-source voltage.Beside,some amendments was introduced todescribe the self-heating effect and the trapping effect to describe the behavior of the devices better.Compared to the traditional model,the proposed model is more accurate in both the saturation region and linear region,which verifies the accuracy of the proposed model.Secondly,the behaviors of GaN HEMT devices will change drastically from the lower temperature limit to the upper temperature limit.When GaN HEMT devices operated at high temperature condition,an accurate temperature dependent model is needed to describe the actual behavior of the devices at different temperatures.In this paper,we tested the ?-?characteristic of the devices from 25? to 300?.The nonlinear current source is sensitive to the temperature by studying the electrical properties of the devices at different temperature conditions.In the paper,a new sequential parameter optimization method is proposed to determine the temperature coefficients of the parameters while minimizing the accumulated error from temperature regression of multiple parameters.Finally,the extented temperature-dependent ?-? model for GaN HEMT devices was established in the entire operating temperature range.Finally,the temperature-dependent model of GaN HEMT device was used to establish wireless sensing unit at high teerature,the bare die and other high-temperature devices will be applied to the high temperature sensing system.Besides,the test platform of high temperature sensing system was set up and the practical circuit was complite by using thick film technology.And the relationship between the oscillation frequency and pressure at different temperatures were obtained by using spectrum analyzer.The comparison of the measured result and the simulated result shows the accuracy of the proposed temperature-dependent model and realize the application of GaN HEMT devices at high temperature.