Enhancement of breakdown voltage in AlGaN/GaN high electron mobility transistors using a field plate

We investigate the breakdown (V/sub br/) enhancement potential of the field plate (FP) technique in the context of AlGaN/GaN power HEMTs. A comprehensive account of the critical geometrical and material variables controlling the field distribution under the FP is provided. A systematic procedure is given for designing a FP device, using two-dimensional (2-D) simulation, to obtain the maximum V/sub br/, with minimum degradation in on-resistance and frequency response. It is found that significantly higher V/sub br/ can be achieved by raising the dielectric constant (/spl epsi//sub i/) of the insulator beneath the FP. Simulation gave the following estimates. The FP can improve the V/sub br/ by a factor of 2.8-5.1, depending on the 2-DEG concentration (n/sub s/) and /spl epsi//sub i/. For n/sub s/=1/spl times/10/sup 13//cm/sup 2/, the V/sub br/ can be raised from 123 V to 630 V, using a 2.2 /spl mu/m FP on a 0.8 /spl mu/m silicon nitride, and 4.7 /spl mu/m gate-drain separation. The methodology of this paper can be extended to the design of FP structures in other lateral FETs, such as MESFETs and LD-MOSFETs.