Influence of Carrier Gases on the Quality of Epitaxial Corundum-Structured α-Ga2O3 Films Grown by Mist Chemical Vapor Deposition Method.

Yu Xu,Ya’Nan Cheng,Qian Feng,Yaolin Cheng,Jincheng Zhang,Zhe Li,Chunfu Zhang,Yue Hao,Dazheng Chen

doi:10.3390/ma12223670

Abstract

This report systematically investigates the influence of different carrier gases (O2, N2, and air) on the growth of gallium oxide (Ga2O3) thin films on c-plane sapphire substrates by using the mist-CVD method. Although XRD and Raman measurements show that the pure corundum-structured α-Ga2O3 with single (0006) plane orientation was successfully obtained for all three different carrier gases, the crystal quality could be greatly affected by the carrier gas. When O2 is used as the carrier gas, the smallest full-width at half maximum (FWHM), the very sharp absorption cutoff edge, the perfect lattice structure, the highest growth rate, and the smooth surface can be obtained for the epitaxial α-Ga2O3 film as demonstrated by XRD, UV-VIS, TEM, AFM (Atomic Force Microscope), and SEM measurements. It is proposed that the oxygen content in carrier gas should be responsible for all of these results. XPS (X-ray photoelectron spectroscopy) analysis also confirms that more oxygen elements can be included in epitaxial film when O2 is used as the carrier gas and thus help improve the crystal quality. The proper carrier gas is essential for the high quality α-Ga2O3 growth.

Highlights

As an ultra-wide-bandgap semiconductor with the obvious advantages of stable physical chemistry, low dielectric constant, and high mechanical strength, gallium oxide (Ga2 O3 ) is attracting increasing attention as a new promising competitor to III-nitrides and SiC for various applications in high-voltage and high-power electronics and ultraviolet optoelectronics [1]
We systematically investigate the influence of different carrier gases (O2, N2, and air) on the film quality for the growth of α-Ga2 O3 on c-plane sapphire substrates by using the mist-CVD
2O3 films show the obvious pure alpha phase. These XRD spectra show that α-Ga2 O3 epilayer and sapphire substrate, respectively

Summary

Introduction

As an ultra-wide-bandgap semiconductor with the obvious advantages of stable physical chemistry, low dielectric constant, and high mechanical strength, gallium oxide (Ga2 O3 ) is attracting increasing attention as a new promising competitor to III-nitrides and SiC for various applications in high-voltage and high-power electronics and ultraviolet optoelectronics [1]. ZnO (3.24 eV) and In2 O3 (3.6 eV), Ga2 O3 has a larger bandgap energy of approximately 5 eV, which means a shorter absorption cutoff wavelength and a much higher power application. Β-Ga2 O3 has a bandgap of 4.8 eV and high Baliga’s figures of merit (FOM) of 3000, which is obviously superior to. Corundum-structured α-Ga2 O3 , another important phase for Ga2 O3 , has a wider bandgap of around 5.3 eV which can result in a larger Baliga’s FOM, Materials 2019, 12, 3670; doi:10.3390/ma12223670 www.mdpi.com/journal/materials

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Conclusion