Electrical and structural characterizations of non-polar AlGaN/GaN heterostructures

A non-polar AlGaN/GaN structure is a strong candidate for the high-voltage device that can operate in enhancement-mode compared to the depletion-mode operation that is practically unavoidable for a standard polar AlGaN/GaN structure. Growth of non-polar GaN is non-trivial and a two-step nucleation scheme was developed to produce high-quality non-polar a-plane AlGaN/GaN structures on r-plane sapphire. The anisotropic nature of non-polar GaN requires a modification to a typical polar GaN-based transistor fabrication process. A KOH wet etch proceeded by a dramatically different mechanism compared to the standard polar c-face AlGaN/GaN structure. This device with Pt/Au Schottky gate displayed a barrier height of 0.76 eV and an ideality factor of 4 at 20 °C.