Numerical study of GaN-on-Si HEMT breakdown instability accounting for substrate and packaging interactions

The electron and hole impact-ionization coefficients in AlxGa1-xN have been calibrated through a Chynoweth law by using a Monte Carlo theoretical study and experimental data at different ambient temperatures. The model has been used to investigate the breakdown characteristics in AlGaN/GaN HEMTs. The concurrent effect of charge trapping in the GaN buffer and impact-ionization generation in the device failure mechanism has been studied by simulating the off-state breakdown under a dc stress. The sensitivity of the AlGaN/GaN HEMT to parasitic charging in molding compound has been investigated by incorporating the passivation and encapsulation layers in the TCAD setup and implementing the conductivity losses in the mold compound at high temperature.