High breakdown voltage AlGaN/GaN HEMT with high-K/low-K compound passivation

A novel high breakdown voltage (BV) AlGaN/GaN high-electron mobility transistor (HEMT) with a high-K/low-K compound passivation layer is proposed. The compound passivation layer is formed by blocks of low-K dielectric (Si₃N₄) embedded in a high-K passivation layer (La₂O₃). Owing to their different dielectric constants, there is a discontinuity of the horizontal electrical field at the high-K/low-K interface, which can introduce a new electric field peak in the nearby channel in the semiconductor and can also modulate the distribution of the electric field along the channel. Hence, enhancement of BV can be achieved. Compared to the typical field-plate structure, high-K/low-K passivation introduces no parasitic capacitance. On the basis of the physical mechanism, several design principles for the high-K/low-K passivation layer are presented. Numerical simulation demonstrates a BV of 1400 V for the proposed device with four blocks of low-K dielectric embedded in a high-K passivation, compared to the BVs of 917 and 288 V for the device with high-K passivation and the device with low-K passivation, respectively.