Study on Al2O3 MOSCAP and Optimization of Atomic Layer Deposited High-k Oxides for AlGaN/GaN MOSHEMT

Abstract

In this thesis, at first an investigation was performed on the properties of atomic-layer-deposited aluminum oxide (Al2O3) on an n-type silicon (n-Si) substrate based on the effect of post-deposition heat treatment, which was speckled according to ambient temperature and treatment applied time. Then, making one step ahead, AlGaN/GaN MOSHEMTs and HEMTs grown on Sapphire substrate were successfully fabricated. Various DC characteristics were extracted. The AlGaN/GaN HEMT suffers from high leakage current and self-heating problem. In order to solve this problem, several combinations of Al2O3 and HfO2 gate dielectrics were applied to the device to suppress the high gate leakage current. In every aspect, the MOSHEMTs have given better performance and all the process conditions along with characteristics are discussed briefly with proper reasoning. So far, in MOSHEMT, single Al2O3 and HfO2 have been widely used as gate dielectric whereas their combination can serve better. The optimization of MOSHEMTs by examining various combinations of Al2O3 and HfO2 nanolaminates and their bilayer is the main goal here.