Cubic GaN/AlGaN Schottky-barrier devices on 3C-SiC substrates
In this work, we focus on the fabrication of cubic GaN based Schottky-barrier devices (SBDs) and measured current voltage (IV) characteristics and the critical field for electronic breakdown. Phase-pure cubic GaN and c-AlxGa1?xN/GaN structures were grown by plasma assisted molecular beam epitaxy (MBE) on 200?m thick free-standing 3C-SiC (100) substrates, which were produced by HOYA Advanced Semiconductor Technologies Co., Ltd. The thickness of the c-GaN and c-Al0.3Ga0.7N epilayers were about 600 and 30nm, respectively. Ni/In Schottky contacts 300?m in diameter were produced on c-GaN and c-Al0.3Ga0.7N/GaN structures by thermal evaporation using contact lithography. A clear rectifying behavior was measured in our SBDs and the IV behavior was analyzed in detail, indicating the formation of a thin surface barrier at the NiGaN interface. Annealing of the Ni Schottky contacts in air at 200C reduces the leakage current by three orders of magnitude. The doping density dependence of breakdown voltages derived from the reverse breakdown voltage characteristics of c-GaN SBDs is investigated. The experimental values of breakdown voltage in c-GaN are in good agreement with theoretical values and show the same dependence on doping level as in hexagonal GaN. From our experimental data, we extrapolate a blocking voltage of 600V in c-GaN films with a doping level ND=51015cm?3.
cubic gan 3c-sic substrates mbe schottky barrier