A novel p-GaN HEMT with superjunction silicon substrate for improved current collapse

Abstract

AlGaN/GaN HEMTs suffer from severe current collapse problems due to the large number of bulk traps within their semi-insulating buffer layer. In this work, a novel p-GaN AlGaN/GaN HEMT with a superjunction silicon substrate is proposed to reduce the buffer-induced current collapse of the device. The buffer-related trapping process of the proposed HEMT was investigated by applying negative V_Sub stress since the surface trapping effect is almost negligible in this case. Under negative V_Sub stress, the superjunction substrate acts like a protective layer for the buffer layer compared to the conventional silicon substrate: it reduces the number of electrons captured within the buffer layer during V_Sub stress by reducing the electric field strength inside the buffer layer and reducing the supply of electrons within the buffer layer. After the V_Sub stress is removed, the reduction in the number of captured electrons in the buffer layer leads to a reduction in the residual negative buffer potential, which in turn leads to a weakening of the depletion effect of the residual buffer potential on the 2DEG. Comparing the simulation results of the proposed HEMT with those of the conventional HEMT, it is demonstrated that the buffer-induced degradation of saturation drain current of the proposed HEMT is effectively suppressed.