Structural characters and band offset of Ga2O3–Sc2O3 alloys

Abstract

Alloy engineering is a promising approach to optimize the electronic properties and application of the ultrawide bandgap semiconductor Ga2O3. Here, the structural and electronic properties of (ScxGa1−x)2O3 alloys are studied using density functional theory with the Heyd–Scuseria–Ernzerhof hybrid functional. Hexagonal (ScxGa1−x)2O3 alloys show more negative formation enthalpies than (AlxGa1−x)2O3 alloys, and the increments in the positive formation enthalpies for monoclinic (ScxGa1−x)2O3 alloys are different from the (AlxGa1−x)2O3 alloys. (ScxGa1−x)2O3 alloys will undergo the compressive strain if grown on the Ga2O3 substrate. The bandgaps range from 4.78 to 5.44 eV for monoclinic (ScxGa1−x)2O3 and from 5.17 to 6.10 eV for hexagonal (ScxGa1−x)2O3. It is noted that Ga2O3/(ScxGa1−x)2O3 heterojunctions keep the type-II band alignments and whose conduction and valence band offsets can be significantly and negligibly enlarged by increasing Sc concentration, respectively. The large conduction band offsets for Ga2O3/(ScxGa1−x)2O3 heterojunctions allow (ScxGa1−x)2O3 alloys to be an electron blocking layer for the Ga2O3 device, and ease the problems of parasitic conduction in the field effect transistor.