Design of 2400-V Off-State Breakdown Voltage in Gate Field-Plate AlGaN/GaN HEMTs Having High- k Passivation Layer and Gate-Drain Distance of 10 μ m

Numerical analysis of off-state drain current-drain voltage and gate current-drain voltage characteristics in gate field-plate AlGaN/GaN HEMTs is performed as parameters of relative permittivity of passivation layer ϵrand field-plate lengthLFP. The gate-drain distanceLGDis 10 μm, and it is discussed when the off-state breakdown voltageVbrbecomes higher than 2400 V. Three cases with ϵr= 7, 20 and 60 are studied, andLFPis changed between 0 and 2 μm. In all the three cases, whenLFPbecomes longer than 0.6 μm,Vbrbecomes lower, and atLFP= 2 μm it becomes 394 V, 389 V and 598 V for ϵr= 7, 20 and 60, respectively. This is because the applied drain voltage drops almost around field-plate edge. When ϵr= 7 (SiN),Vbrbecomes a peak (2161 V) atLFP= 0.3 μm because the electric field around gate edge is suppressed and high-field area spreads toward the drain. But, it is lower than 1000 V whenLFP≤ 0.2 μm andLFP> 0.6 μm. When ϵr= 20,Vbrbecomes 1840 V atLFP= 0.1 μm and 2420 V atLFP= 0.2 μm because the high-filed area spreads toward the drain but it does not reach the drain.Vbris higher than 1840 V betweenLFP= 0.1 and 0.3 μm. On the other hand, when ϵr= 60,Vbrbecomes 2560 V atLFP= 0.1 μm and 2781 V atLFP= 0.2 μm because the high-field area reaches the drain and electric field profiles along gate to drain become relatively uniform.Vbrbecomes higher than 2400 V betweenLFP= 0.1 and 0.3 μm. Achieving highVbrfor shortLFPis favorable because of low parasitic capacitance. A higher ϵrcase of 100 without a field plate is also investigated. It is shown thatVbrbecomes as high as 2403 V because the electric field around gate edge is suppressed and electric field profiles along gate to drain become rather uniform.