Evolution of optical properties and band structure from amorphous to crystalline Ga2O3 films

Fabi Zhang,Guo-Ling Li,Yi-Tao Cui,Haiou Li,Qixin Guo

doi:10.1063/1.5021867

Abstract

The optical properties and band structure evolution from amorphous to crystalline Ga2O3 films was investigated in this work. Amorphous and crystalline Ga2O3 films were obtained by changing the growth substrate temperatures of pulsed laser deposition and the crystallinity increase with the rising of substrate temperature. The bandgap value and ultraviolet emission intensity of the films increase with the rising of crystallinity as observed by means of spectrophotometer and cathodoluminescence spectroscopy. Abrupt bandgap value and CL emission variations were observed when amorphous to crystalline transition took place. X-ray photoelectron spectroscopy core level spectra reveal that more oxygen vacancies and disorders exist in amorphous Ga2O3 film grown at lower substrate temperature. The valence band spectra of hard X-ray photoelectron spectroscopy present the main contribution from Ga 4sp for crystalline film deposited at substrate temperature of 500 oC, while extra subgap states has been observed in amorphous film deposited at 300 oC. The oxygen vacancy and the extra subgap density of states are suggested to be the parts of origin of bandgap and CL spectra variations. The experimental data above yields a realistic picture of optical properties and band structure variation for the amorphous to crystalline transition of Ga2O3 films.

Highlights

One of the keys to the fabrication of β-Ga2O3 based devices such as chips can be regarded as the deposition technology, since the microelectronic solid-state devices are almost based on material structures created by thin film deposition
The crystallinity of the films was varied by changing the substrate temperature because previous work observed amorphous to crystalline transition with the increasing of substrate temperatures.[25]
Hard X-ray photoemission spectroscopy (HAXPES) reveals the existence of oxygen vacancy, disorder and extra subgap density of states in amorphous Ga2O3 films deposited at low substrate temperature, which should account for the variation of optical properties of Ga2O3 films

Summary

Introduction

One of the keys to the fabrication of β-Ga2O3 based devices such as chips can be regarded as the deposition technology, since the microelectronic solid-state devices are almost based on material structures created by thin film deposition. Evolution of optical properties and band structure from amorphous to crystalline Ga2O3 films

Results

Conclusion