Structural and interface band alignment investigations on epitaxial β-Ga2O3/α-GaCrO3 type-II transparent heterojunction

Abstract

Herein, we investigate structural and electronic properties of β-Ga2O3 and p-type Ni-doped α-GaCrO3 (α-GaCrO3:Ni) heterostructure, focusing on its potential for charge separation and rectification mechanisms. Thin films are grown using the magnetron sputtering technique. Synchrotron-based high-resolution x-ray diffraction and high-resolution transmission electron microscopy reveals a sharp and high-quality interface between β-Ga2O3/α-GaCrO3:Ni/Al2O3 epitaxial layers and also confirm single-crystal epitaxial growth of monoclinic (−201) β-Ga2O3 along the [0001] direction of α-GaCrO3:Ni. Optical measurements confirm an average transmission of more than 70% for all thin film samples, showing their potential for transparent optoelectronic devices. Using synchrotron-based photoelectron spectroscopy, valence band offset and conduction band offset at β-Ga2O3/α-GaCrO3:Ni interface are determined to be 2.44 ± 0.2 and 1.44 ± 0.2 eV, respectively, which confirms a type II (staggered gap) energy band alignment at the heterojunction. This type of band alignment is highly useful in a wide range of photovoltaic and optoelectronic devices where efficient charge separation, reduced recombination, and rectification of charge carriers play an important role, such as in solar cells, UV photodetectors, and many other optoelectronic devices.