Bandgap modulation and electrical characteristics of (AlxGa1−x)2O3/4H-SiC thin film heterostructures

Abstract

In this work, (AlxGa1−x)2O3 thin films were grown on a 4H-SiC substrate by radio frequency (RF) sputtering. (AlxGa1−x)2O3 targets with different nominal Al content xt: 0, 0.1, 0.4, 0.8, and 1 were used for RF sputtering. Samples were subsequently annealed at 800 °C to enhance film crystallinity. X-ray diffraction analysis revealed the improved crystallinity for increased Al content (xt), ranging from a ratio of 0 to 0.4 (in relation to Al+Ga content). The films with Al content of 0.8 and 1 exhibited poor crystallinity. The chemical compositions of the Al, Ga, and O atoms were consistent with those of the sputtering targets. Furthermore, the analysis of the inelastic energy loss from X-ray photoelectron spectroscopy confirmed that bandgap tuning is possible for (AlxGa1−x)2O3 using the RF sputtering method. Hall mobility improved up to 17.1%, from 21.90 (xt: 0) to 25.65 (xt: 0.4) cm2V−1s−1. I−V characteristics corresponded well with the Hall measurement. Therefore this study effectively demonstrated the tuning of the bandgap of (AlxGa1−x)2O3 by varying the Al composition. Further, the electrical properties of the (AlxGa1−x)2O3 can be improved or maintained from that of conventional Ga2O3 devices by optimizing the growth ambient.