Analysis of breakdown characteristics of field-plate AlGaN/GaN HEMTs with a high-k passivation layer

It is well known that the introduction of field plate increases the breakdown voltage V_br of AlGaN/GaN HEMTs. As another way to improve V_br, using a high-k passivation layer is proposed. So, in this study, we combine the two factors and analyzed the breakdown characteristics of field-plate AlGaN/GaN HEMTs as parameters of its rength L_FP and the relative permittivity of passivation layer er. It is shown that the enhancement of V_br with increasing ϵ_τ is more significant when L_FP is relatively short. There is an optimum value of L_FP to obtain the highest V_br, and it is around 0.2 and 0.3 μm when the gate-to-drain distance is 1.5 μm When L_FP = 0.3 μm and ϵ_τr takes a high value of 50, the electric field between the field-plate edge and the drain becomes rather uniform, and V_br becomes about 400 V, which corresponds to an effective electric field of 2.7 MV/cm between gate and drain.