Influence of a drain field plate on the forward blocking characteristics of an AlGaN/GaN high electron mobility transistor

In this paper, the influence of a drain field plate (FP) on the forward blocking characteristics of an AlGaN/GaN high electron mobility transistor (HEMT) is investigated. The HEMT with only a gate FP is optimized, and breakdown voltage V_BR is saturated at 1085 V for gate–drain spacing L_GD ≥ 8 μm. On the basis of the HEMT with a gate FP, a drain FP is added with L_GD=10 μm. For the length of the drain FP L_DF ≤ 2 μm, V_BR is almost kept at 1085 V, showing no degradation. When L_DF exceeds 2 μm, V_BR decreases obviously as L_DF increases. Moreover, the larger the L_DF, the larger the decrease of V_BR. It is concluded that the distance between the gate edge and the drain FP edge should be larger than a certain value to prevent the drain FP from affecting the forward blocking voltage and the value should be equal to the L_GD at which V_BR begins to saturate in the first structure. The electric field and potential distribution are simulated and analyzed to account for the decrease of V_BR.