Temperature Dependence of β-Ga2O3 Heteroepitaxy on c-plane Sapphire using Low Pressure Chemical Vapor Deposition
Abstract
β-Ga2O3 has drawn significant attention for power electronics and deep ultraviolet (UV) photodetectors owing to its wide bandgap of ~ 4.4 - 4.9 eV and high electric breakdown strength ~7-8 MV/cm. Growth of β-Ga2O3 epitaxial thin films with high growth rate has been recently reported using low pressure chemical vapor deposition (LPCVD) technique. In this work, we have investigated the effect of growth temperature on β-Ga2O3 films grown on c-plane sapphire substrates using LPCVD. We performed growths by varying temperatures from 800C to 950C while keeping all other growth parameters (Ar/O2 gas flow rates, growth pressure, and Gallium precursor to substrate distance) constant. Optical, structural, and surface characterizations are performed to determine the bandgap, phase purity, crystal orientation, and crystalline quality of the grown thin films. Amorphous islands of Ga2O3 are observed at growth temperature of 800C while continuous and crystalline (-201) oriented β-Ga2O3 thin films are achieved for growth temperatures of 850C to 950C. Crystallinity of the films is found to improve with increase in growth temperature with a minimum rocking full width at half maximum of 1.52 in sample grown at 925C. For all the samples grown at and above 875C, transmittance measurements revealed an optical bandgap of ~4.77-4.80 eV with high growth rate of ~6 μm/hr.
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