Research On The Influence Of Defects On The Reliability Of GaN-based MIS-HEMT

AlGaN/GaN MIS-HEMT device is gaining increasing attention in the field of high temperature,high frequency,and high power power electronic devices for its attractive performance,including high temperature resistance,high pressure resistance,and radiation resistance.Although GaN-based HEMT devices have developed rapidly,the traps in the body material or the interface causes problems such as current collapse and threshold voltage drift,which seriously affect the reliability of the device and restrict the large-scale application of the device.Therefore,in order to realize the commercial application of GaN-based HEMT devices,the influence law and physical mechanism of defects on device degradation are urgently needed to be studied.In this context,the effect of defects in AlGaN/GaN MIS-HEMT devices on the degradation of the devices under open-state stress is investigated.In this paper,the law of MIS-HEMT device defects affecting device performance degradation is studied by simulation analysis firstly.To investigate the effect of different defects on device performance,Sentaurus TCAD is used.By changing the concentration,energy level and locations of the defect,the influence on the electrical characteristics of the MIS-HEMT device is specifically studied.It is found that the degradation of the device performance is caused by the traps in the device through the hot electron effect,which cause saturation drain current reducing and threshold voltage shifting.Among the traps in bulk material,the traps in GaN buffer layer have the greatest impact on the degradation of electrical characteristics of MIS-HEMT devices.To further study the degradation mechanism,the gate field plate structure is used.It indicates that the traps in GaN buffer layer have a greater probability of trapping hot electrons.In addition,deep-level acceptor defects have a greater impact on the electrical characteristics of MIS-HEMT devices than shallow-level acceptor defects;the degradation of the device increases with the increase of trap concentration.To investigate the influence of the interface state on the electrical performance of the device,AlGaN/GaN MIS-HMETs with different gate dielectric materials(HfO2 and SiNX)have been fabricated.First,the MIS-HEMT with HfO2 gate dielectric has higher maximum output current density(386 mA/mm)and superior subthreshold swing(73mV/dec)than the device with SiNX gate dielectric.Besides,the device with HfO2 gate dielectric has lower on-resistance(8 Ω·mm)and higher Gm(160 mS/mm),leading to better performance.The improved frequency-dependent C-V measurement is used to characterize the interface trap density(Dit).And it indicates that the drift of the threshold voltage is caused by the interface state defects,and the greater the density of the interface defects,the greater the drift of the threshold voltage.Then the activation energy in the process of trapping electrons by the interface state defects is analysed through the variable temperature positive gate compressive stress experiment,and the activation energy is fitted through the variable temperature stress test and the tensile index model,which verifies that the SiNx gate dielectric device has better interface quality.And explained the source of the high interface state density of HfO2 gate dielectric devices.Finally,through the combination of simulation and experimental results,it indicates that the deep-level defects at the interface between the AlGaN barrier layer and the dielectric layer dominate the degradation of the threshold voltage of the MIS-HEMT device.This work provides the basic theory for improving the reliability of AlGaN/GaN MIS-HEMT devices.