Optical and electronic properties of (AlxGa1-x)2O3/Al2O3 (x > 0.4) films grown by magnetron sputtering

Systematic investigations of the optical and electronic properties are reported for ultrathin (AlxGa1-x)(2)O-3/Al2O3 films with higher Al contents x (> 0.4) prepared by magnetron sputtering method. The X-ray diffraction results revealed the films were preferentially oriented in the direction of beta-Ga2O3 ((2) over bar 01) family and their crystalline qualities improved if prepared at higher sputtering power. From the X ray photoelectron spectroscopy (XPS) data, the Al content x in the four (AlxGa1-x)(2)O-3 samples are found to be 0.72, 0.67, 0.62 and 0.42, respectively. The composition dependent energy bandgaps E-g (6.47 eV, 6.34 eV, 6.02 eV, 5.61 eV) observed by optical transmission and XPS measurements are examined theoretically. From the atomic ratios of (Al+Ga)/O and the observed photoluminescence features we suggest the possibility of large number of defects and/or vacancies. With higher Al contents, the Fermi level shifts towards the valence band and the work function increases. While lowering the sputtering power is helpful in preparing thin (A1(x)Ga(1-x))(2)O-3 films with higher x - it is certainly not favorable for improving their crystalline quality and conductivity. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Systematic investigation was conducted on ultrathin (AlxGa1-x)(2)O-3/Al2O3 films with higher Al content prepared by magnetron sputtering method. The films showed improved crystalline quality with higher sputtering power, and increasing Al content led to a shift in Fermi level towards the valence band and an increase in work function. However, the higher Al content also suggested the possibility of a large number of defects or vacancies.