Influence of the carrier behaviors in p-GaN gate on the threshold voltage instability in the normally off high electron mobility transistor.

Threshold voltage (V_TH) instability has been studied in the as-fabricated p-GaN gated enhancement-mode high electron mobility transistors (p-GaN E-HEMTs) under a positive gate stress. A negative V_TH shift (ΔV_TH) obtained by dynamic measurement has been observed more severely when compared to the static one. The V_TH deviation is attributed to the complicated influence of carrier transport behaviors in the p-GaN gate. The impacts of hole accumulation, trapping, and consumption on the V_TH instability and drain current variation can be effectively distinguished according to the transfer characteristics obtained from the pulse I–V measurement. Moreover, the density of hole traps in the p-GaN gate is estimated to be around ∼2 × 10¹¹ cm⁻² by the capacitance–voltage measurement, and the energy level is calculated to be around E_V + 0.62 eV by fitting the recovery curve of gate current after positive gate bias. This study focusing on the in-depth influence of different carrier behaviors on the gate performance can help with the understanding and further improvement of the dynamic instability and reliability of the GaN-based HEMTs. [ABSTRACT FROM AUTHOR]