EXPLORATION OF GALLIUM OXIDE DEVICES FOR POWER APPLICATIONS

Abstract

Beta gallium oxide (β-Ga₂O₃) is an emerging candidate for the next generation of power devices, particularly Schottky barrier diode (SBD) and metal-oxide-semiconductor field-effect transistors (MOSFET). However, the development of Ga₂O₃ power device fabrication is still at its early stage. This thesis addresses and proposes solutions for issues that are still problems for Ga₂O₃ based devices. The first part of the thesis demonstrates a method to improve the SBD’s subthreshold slope (61 mV/dec) and uniformity across the wafer by inserting an Al-reacted interfacial layer between the metal and semiconductor. Despite the exceptional characteristics of the Ga₂O₃ SBD, the lack of p-type Ga₂O₃ is preventing it from achieving even higher voltage blocking capability. In the second part, solutions to achieve p-type alternatives for Ga₂O₃ are investigated, including heterojunctions based on NiO_x/Ga₂O₃ and Ga₂O₃/p-GaN, and current blocking layer based on Mg-Ga₂O₃. The unipolar operation characteristic of Ga₂O₃ also raises concerns for Ga₂O₃-based metal-oxide-semiconductor field-effect-transistor (MOSFET), as conventional Ga₂O₃ MOSFET typically operate in depletion-mode (D-mode). In the final segment of the thesis, an innovative approach is presented, which introduces an enhancement-mode (E-mode) Ga₂O₃ MOSFET based on charge trapping layer (CTL) technique.