Bandgap Tailoring Of Monoclinic Single-Phase Beta-(Alxga1-X)(2)O-3 (0 <= X <= 0.65) Thin Film By Annealing Beta-Ga2o3/Al2o3 Heterojunction At High Temperatures

Herein, bandgap tuning of monoclinic (-201)-oriented beta-(AlxGa1-x)(2)O-3 thin films is achieved through a beta-Ga2O3/Al2O3 heterojunction by a feasible annealing process with an O-2 atmosphere. During the annealing process, Al atoms of the Al2O3 substrate outdiffuse easily into the beta-Ga2O3 thin film deposited by ozone-assisted molecular beam epitaxy (OMBE). The Al compositions in the beta-(AlxGa1-x)(2)O-3 samples are tuned through adjusting the annealing temperature from 800 to 1300 degrees C and experimentally determined from the result of X-ray photoelectron spectroscopy (XPS) measurements combined with Vegard's law. Successive Al-composition-gradient beta-(AlxGa1-x)(2)O-3 thin films with controlled bandgap are constructed. On these bases, beta-Ga2O3 thin films are deposited on beta-(AlxGa1-x)(2)O-3 (0 <= x <= 0.65) substrates through OMBE, yielding beta-Ga2O3/beta-(AlxGa1-x)(2)O-3 (0 <= x <= 0.65) heterojunction structures, and the band offsets of this heterojunction are determined by XPS accordingly. This methodology to achieve high-quality beta-(AlxGa1-x)(2)O-3 thin films with adjustable Al composition and tunable band offsets of the beta-Ga2O3/beta-(AlxGa1-x)(2)O-3 interface will provide guidance for potential strategies to develop and fabricate beta-(AlxGa1-x)(2)O-3-based deep-UV photodetectors and power devices.