Study Of Millimeter-wave GaN Based HEMT Device

The extraordinary electrical characteristics of GaN material make the GaN basedHEMT an important candidate for millimeter wave power device.In this paper, the researchprogress was summaried, and the significance of millimeter wave GaN based HEMT wasillustrated. The basic device structure and principles of GaN based HEMT were introduced.The study of GaN based HEMT based on device simulated. Based on the precisechoose of the physics model and parameters in the new generation TCAD tool-sentaurusDevice, the simulation of GaN based HEMT was carried out. The influence of geometrysize of the T shape gate on the fT/fmaxwas analysed for the real device fabrication. Theconclusions can be obtained via the device simulation: the width of gate cap affect Rg, Cgsand Cgdsimultaneously. The fmaxincrease with the decrement of the gate length.The research of short channel effect on the DC and RF performance of millimeter waveGaN based HEMT. When the gate length come into below50nm, the gate control abilitydegenerate and sub-threshold current increase acutely, the max trans conductance decreaseand drift of threshold voltage become severe, leading to degradation of the frequency andpower characteristics. The change of fTwas analysed, when the gate lenth change fromto,the fT Lg degenerate from to. The influence of aspect ratio on the RF performancedegradation was studied. when aspect ratio come into below6,the drift of threshold voltageis above25%, and the fT Lg degenerate about32%.The establishment of the small signal equivalent circuit model of the GaN basedHEMT. Based on the traditional extraction methods, the effect of channel distributedresistance and gate differential resistance was minimized by calculation of cold field zparameters. The nature Y parameters were obtained by the analysis of hot field parameters.The simulation results is in accordance with measured data. Compared with the traditionalmodel, gate differential resistance Rfsand Rfdwere introduced to characterize the gateleakage current.