Trapping Effects Induced by Gate OFF-State Stress in AlGaN/GaN High-Electron-Mobility Transistors with Fe-Doped Buffer

This paper investigates the trapping characteristics in passivated Al_0.23Ga_0.77N/GaN High-Electron-Mobility transistors (HEMTs) with an Fe-doped buffer on Sapphire substrate. Double pulsed current–voltage (I–V) measurements clearly exhibited the current collapse and slow detrapping transients characteristics. It is attributed to the injection of electron from gate to the traps located in the interface, the Al_0.23Ga_0.77N barrier and the Fe-doped buffer. By various pulse-widths of 0.5 μs, 5 μs, 10 μs, 50 μs and 0.1 ms and amplitudes of pulse-baseline (V _GS-Q) of −6 V and −8 V, we spatially analyzed the locations and corresponding detrapping time constants of the dominant traps in the device. Three different types of traps were found: a fast one with the time constant τ = 12–16 μs at the interface under gate, a middle one with τ = 0.12 ms in the AlGaN barrier layer, and a slow one in the Fe-doped GaN buffer under high reverse OFF-state stress with τ = 1.78 ms. Thus in the high voltage applications, the buffer-related deep traps are most significant.