Structural characters and band offset of Ga2O3-Sc2O3 alloys

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)(2)O-3 alloys are studied using density functional theory with the Heyd-Scuseria-Ernzerhof hybrid functional. Hexagonal (ScxGa1-x)(2)O-3 alloys show more negative formation enthalpies than (AlxGa1-x)(2)O-3 alloys, and the increments in the positive formation enthalpies for monoclinic (ScxGa1-x)(2)O-3 alloys are different from the (AlxGa1-x)(2)O-3 alloys. (ScxGa1-x)(2)O-3 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)(2)O-3 and from 5.17 to 6.10 eV for hexagonal (ScxGa1-x)(2)O-3. It is noted that Ga2O3/(ScxGa1-x)(2)O-3 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)(2)O-3 heterojunctions allow (ScxGa1-x)(2)O-3 alloys to be an electron blocking layer for the Ga2O3 device, and ease the problems of parasitic conduction in the field effect transistor.

Automated summary

The structural and electronic properties of (ScxGa1-x)(2)O-3 alloys were investigated. It was found that (ScxGa1-x)(2)O-3 alloys have more negative formation enthalpies compared to (AlxGa1-x)(2)O-3 alloys, and the increments in positive formation enthalpies of monoclinic (ScxGa1-x)(2)O-3 alloys are different from (AlxGa1-x)(2)O-3 alloys. Compressive strain is observed when (ScxGa1-x)(2)O-3 alloys are grown on Ga2O3 substrate. The bandgaps range from 4.78 to 5.44 eV for monoclinic (ScxGa1-x)(2)O-3, and from 5.17 to 6.10 eV for hexagonal (ScxGa1-x)(2)O-3. Ga2O3/(ScxGa1-x)(2)O-3 heterojunctions maintain type-II band alignments, and the conduction and valence band offsets can be significantly and negligibly enlarged by increasing Sc concentration, respectively. (ScxGa1-x)(2)O-3 alloys can serve as an electron blocking layer for Ga2O3 devices, thus alleviating parasitic conduction issues in field effect transistors.