Investigation of the Electrical Properties of (InxGa1-x)2O3 Alloys Grown using Pulsed Laser Deposition
Date
2022-12
Authors
Saha, Puja Rani
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Abstract
Wide bandgap semiconductor materials are gaining popularity because of their favorable features for increased power and high breakdown performance. Beta-gallium oxide (β-Ga2O3) is one such material with direct bandgap of 4.9eV having exceptional thermal and chemical stability. Materials that can preserve favorable energy alignment when manufacturing heterojunctions and alloys are needed to improve device performance. Thus, studying the bandgap engineering susceptibility and surface electrical characteristics of In2O3 and β-Ga2O3 alloys can lead to the discovery of a plethora of new potential applications. (InxGa1-x)2O3 alloys have highly tunable electrical and optical properties that can be used in transparent conductor technologies and solar-blind photodetectors. As a result, it is critical to develop an understanding of the structural and electrical behavior of these metal oxide alloys. In this research, alloys of Ga2O3 with In2O3, ternary (InxGa1–x)2O3 were grown for x =25% as a function of growth parameters such as substrate temperature (Ts), and oxygen partial pressure (Po2) using Pulsed Laser Deposition (PLD) technique. Amorphous to crystalline phase transformation was observed with increasing substrate temperature. Crystalline phases were detected representing both the monoclinic and cubic bixbyite phases. Ellipsometry study showed a slight thickness variation due to evaporation of volatile Ga2O and In2O suboxides. Temperature dependent Hall measurement analysis showed mobility and resistivity of the alloys are of the order ~ 14-30 cm2 /Vs and ~7×10-2 -9×10-2 Ω.cm respectively. Higher mobility was observed for the amorphous alloys compared to the crystalline samples. X-ray photoelectron spectroscopy (XPS) analyses indicated that the (InxGa1–x)2O3 alloy contains a mixture of Ga and In cation valence states and oxygen vacancies were reduced when the oxygen partial pressure during deposition was increased. The reduction of the oxygen vacancies was attributed to the suppression of internal defects due to the oxygen vacancies. Thus, reduction of the oxygen vacancies was thought to be a possible reason of increasing mobility with increasing partial pressure for the crystalline alloys. To further investigate the role of the reduction of internal defects, (InxGa1–x)2O3 alloys were deposited on sapphire substrate with a Ga2O3 buffer layer. The homoepitaxial buffer layer successfully increased the mobility of the crystalline alloys consistent with reducing the internal defects.
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Keywords
ultra-wide bandgap, heterostructure, PLD, electrical conductivity, XRD, XPS, ellipsometry, PPMS
Citation
Saha, P. R. (2022). Investigation of the electrical properties of (InxGa1-x)2O3 alloys grown using pulsed laser deposition (Unpublished thesis). Texas State University, San Marcos, Texas.