Possible Origin of Near‐Interface Donor‐Like Defects in p‐Type Gallium Nitride Metal–Oxide–Semiconductor Structures

The origin of near‐interface donor‐like defects at the Al 2 O 3 /p‐type gallium nitride (p‐GaN) interface formed by atomic layer deposition is investigated in metal–oxide–semiconductor structures. In the sample with 800°C/30 min dehydrogenation annealing, a large horizontal shift of the capacitance–voltage ( C–V ) curve toward negative voltages compared with the ideal curve is observed, which indicates the existence of near‐interface donor‐like defect states at the Al 2 O 3 /p‐type GaN interface. With increasing annealing temperature up to 850°C, the horizontal shift markedly decreases. Further reduction in C–V curve shift is achieved by the photoelectrochemical (PEC) etching of the p‐GaN layer before 850°C dehydrogenation annealing. The doping profiles show that the acceptor compensation is reduced in the sample with PEC etching, which proves that the diffusion source of donor‐like defects is initially located near the GaN surface. On the basis of C–V measurements, near‐interface donor‐like defect states were detected at 0.5 eV above the valence band edge. The photoluminescence spectra obtained at 10, 300, and 500 K indicate that the yellow/green luminescence peak intensity is reduced by PEC etching. Consequently, the origin of the near‐interface donor‐like defects is highly likely to be nitrogen vacancies.