Normally-off InAlN/GaN HEMTs with n ++ GaN cap layer: A simulation study

The ongoing interest in the development of GaN-based enhancement-mode high electron mobility transistors (EHEMTs) resulted in several different approaches being proposed, one of them employing a reduction of the gate-to-channel distance. In order to facilitate gate recessing, a technique using a n++ cap layer was suggested by Kuzmik et al. [1], who also analyzed the contribution of the cap layer to current conduction and on the mechanism of the off-state breakdown. In this work we complement the experimental results with two-dimensional device simulation using Minimos-NT [2]. We have employed it previously for the optimization studies of a whole generation of AlGaN/GaN HEMTs [3], but also for high-temperature simulations [4].