The Research On Test And Simulation Of GaN HEMT Devices

Since twenty-first century,GaN-based high electron mobility transistor?HEMT?is widely used in microwave communication,radar and other fields for its high thermal conductance,high frequency,and high power density.Although the performance of the device has been improved,the reliability of degradation and failure of GaN HEMTs is still a key factor that limits the development.Researches on thermal characteristics,the degradation and failure mechanism of electrical performance of this device have always been a hotspot.In this paper,the thermal characteristics,defects and failure analysis of GaN HEMTs were studied and discussed by simulation and experiments.This paper is supported by the two projects of 863 Program?2015AA033304 and 2015AA033305?.The main research contents are as follows:?1?Aiming at the problem that the GaN HEMTs are easy to produce self-oscillation,the anti-self-excitation test protection circuit was designed.The effect of high temperature on the DC characteristics,gate leakage characteristics and source/drain series resistance of GaN HEMT devices was studied,and the possible influence mechanisms were given according to the experimental results.The thermal resistance of GaN HEMT was analyzed by the electrical method and infrared method.The thermal resistances of the device under different test current values were compared and analyzed.The thermal resistances of the device under the same power and different drain source voltages were measured,and results show that the junction temperature is higher under high voltage.?2?The thermal characteristics and defects problem of GaN HEMT devices were studied and analyzed using Silvaco-ATLAS semiconductor device simulation software.In the simulation model,the influence of trap effect and lattice thermal motion on the performance of GaN HEMT were considered,the self-heating effect and lattice heat distribution of GaN HEMTs were simulated,and the relationship between lattice thermal distribution and electric field distribution was analyzed.The effects of Si₃N₄/AlGaN interface defect,AlGaN layer defect and GaN layer defect on the output characteristics of the device were studied.Furthermore,the influence of the defect concentration and the defect level on the output characteristics of the device was analyzed.?3?A failure analysis method for electrical stress failure of GaN HEMTs was designed based on common electrical stress failure,and a corresponding case analysis was presented.Following the unique complementary detection process of electrical testing,thermal radiation and photon emission,device failure position can be determined and failure mode and mechanism can be analyzed by this method.A 4-finger GaN-based HEMT with an operating voltage of 28V and a gate width of 1.25mm was analyzed according to this failure analysis method.Two failure positions were localized and the failure mode and mechanism were determined by comprehensive analysis of testing images and data.Finally,several improvements on design and process of GaN-based HEMTs were proposed.