Characteristics And Failure Mechanism Of AlGaN/GaN HEMT Devices Under High Stress

As the first and second generation of semiconductor materials,silicon and gallium arsenide have greatly promoted the development of microelectronics.However,these materials cannot meet the requirements of high temperature,high frequency,high pressure and high power because of the physical property limitations.At the same time,GaN materials have become research focus in the field of semiconductors and are treated as the potential alternative material of the third generation semi-conductor due to the larger band gap,higher breakdown voltage,larger carrier mobility and higher thermal conductivity of GaN.However,problems such as high impurity content,many defects and large dislocation density hinder the development of AlGaN/GaN HEMT.Extensive studies have shown that low frequency noise can characterize defects,and it is no-destructive,sensitive and fast.The characteristics and failure mechanism of AlGaN/GaN HEMT devices under high stress conditions are studied.The main contents are as follows:（1）The electrical parameter degradation and corresponding detrap effect of AlGaN/GaN HEMT devices in the temperature range of 25°C to 125°C are investigated.It show that transfer curves negatively shift,trans-conductance degrades,and the gate leakage current I_G and the subthreshold current I_DS increases with the increase in temperature at DC experiment conditions.It is discussed by the forward-reverse diode experiment,double pulse experiment and gate delay experiment that the screw dislocation in the AlGaN barrier layer may provide an electron detrapping path,so that the detrapping effect is enhanced at higher temperatures,and electrons are easily captured,and causes the device electrical parameters to degrade.The low-frequency G-R noise technique determines that the activation energy required for electrons to be detrapped from thermal defects is 0.521 eV.（2）The degradation mechanism of AlGaN/GaN HEMT devices under high temperature storage is investigated.It show that the drain-source current I_DS increases,and the threshold voltage V_TH drifts negatively after high-temperature storage.According to the drain delay experiment,forward-reverse diode experiment and capacitance-voltage experiment,it is hinted that the electrons in the shallow-donor impurities in the GaN buffer layer under high temperature storage are excited into the triangular well and the interface state of the gate and AlGaN barrier layer is increased.Thus,the increase in the two-dimensional electron surface density and the decrease in the density of the interface state of the heterojunction degrade device.（3）The degradation mechanism of AlGaN/GaN HEMT devices under high temperature reverse bias is studied.It show that the drain current source I_DS decreases,and the threshold voltage V_TH drifts positively after high temperature reverse bias.The double-pulse experiment,gate delay experiment and reverse-forward diode experiment prove that the electrons trapped by surface states of AlGaN and the defect effect are the main reasons for device degradation.It is shown by low frequency 1/f noise that the defect state density is obtained from 8.3E18cm^-3eV^-1 to 1.4E19 cm^-3eV^-1 to quantify the degree of degradation.