Schottky diodes and high electron mobility transistors of 2DEG AlGaN/GaN structures on sapphire substrate

Abstract

We report Schottky diodes (SDs) and High Electron Mobility Transistors (HEMTs) fabricated of 2DEG AlGaN/GaN structures grown by Metalorganic Chemical Vapour Phase Epitaxy (MOVPE) on sapphire substrate. The SDs and HEMTs were designed intentionally without surface passivation and were successfully fabricated at the Center for Physical Sciences and Technology (CPST), using standard UV photolithography procedures. The performance of Ohmic contacts formed of quaternary Ti/Al/Ni/Au stack was optimized varying the temperature of rapid thermal annealing process. Deposited on the semiconductor metal Ni/Au stack was used to form 0.75 eV height Schottky barriers. The fabricated SDs demonstrated low reverse current and high electric current switching ratio while the HEMTs showed high transconductance and drain saturation currents performance with good transistor channel closing. This work paves a way to develop advanced AlGaN/GaN based HEMT structures as well as new electronic components for operation at high powers and high frequencies.