Abstract
Gallium oxide (Ga2O3) is an emerging wide bandgap semiconductor that has attracted a large amount of interest due to its ultra-large bandgap of 4.8 eV, a high breakdown field of 8 MV/cm, and high thermal stability. These properties enable Ga2O3 a promising material for a large range of applications, such as high power electronic devices and solar-blind ultraviolet (UV) photodetectors. In the past few years, a significant process has been made for the growth of high-quality bulk crystals and thin films and device optimizations for power electronics and solar blind UV detection. However, many challenges remain, including the difficulty in p-type doping, a large density of unintentional electron carriers and defects/impurities, and issues with the device process (contact, dielectrics, and surface passivation), and so on. The purpose of this article is to provide a timely review on the fundamental understanding of the semiconductor physics and chemistry of Ga2O3 in terms of electronic band structures, optical properties, and chemistry of defects and impurity doping. Recent progress and perspectives on epitaxial thin film growth, chemical and physical properties of defects and impurities, p-type doping, and ternary alloys with In2O3 and Al2O3 will be discussed.
Highlights
TO Ga2O3 AND APPLICATIONSGallium oxide (Ga2O3) is an emerging ultra-wide bandgap (UWBG) semiconductor that has attracted a large amount of interest due to its ultra-large bandgap of 4.8 eV, high thermal stability, and availability of large-scale native substrates for mass production
This review aims to provide an updated account of the semiconductor physics of Ga2O3 in terms of electronic structures, optical properties, chemistry of defects and dopants, and bandgap engineering
The activation energy (Ea) for donors depend on the doping concentration (Nd), i.e., Ea decreases with an increase in Nd, resulting from a combined effect of screening of the dopant’s Coulomb potential by free carriers and charged impurities and of spatial fluctuations of the conduction band (CB) edge induced by the potentials of randomly distributed charged impurities
Summary
Gallium oxide (Ga2O3) is an emerging ultra-wide bandgap (UWBG) semiconductor that has attracted a large amount of interest due to its ultra-large bandgap of 4.8 eV, high thermal stability, and availability of large-scale native substrates for mass production. Great improvements have been made in the growth of bulk crystals and epitaxial layers, more precise control over defects and impurities as well as deeper understanding on the origin of unintentional defects, deep level trap states, carrier transport mechanism, and so on need more investigations; this is considerably important since these defects, doping, and deep level states largely determine the device operation, output power, threshold voltage, and carrier mobility by causing carrier compensation, scattering, and trapping effects. Recent progress and fundamental understanding on synthesis of bulk single crystals, epitaxial thin film growth, chemical and physical properties of defects and impurities, and origin of unintentional n-type doping, p-type doping, and ternary alloys with In2O3 and Al2O3 were discussed
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