paper

Band gap and band offset of Ga $_{2}$ O $_{3}$ and (Al $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ alloys

arXiv:1806.03360 · doi:10.1103/PhysRevApplied.10.011003

Abstract

Ga $_{2}$ O $_{3}$ and (Al $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ alloys are promising materials for solar-blind UV photodetectors and high-power transistors. Basic key parameters in the device design, such as band gap variation with alloy composition and band offset between Ga $_{2}$ O $_{3}$ and (Al $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ , are yet to be established. Using density functional theory with the HSE hybrid functional, we compute formation enthalpies, band gaps, and band edge positions of (Al $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ alloys in the monoclinic ( $I^^{2}$ ) and corundum ( $I^\pm$ ) phases. We find the formation enthlapies of (Al $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ alloys are significantly lower than of (In $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ , and that (Al $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ with $x$ =0.5 can be considered as an ordered compound AlGaO $_{3}$ in the monoclinic phase, with Al occupying the octahedral sites and Ga occupying the tetrahedral sites. The direct band gaps of the alloys range from 4.69 to 7.03 eV for $I^^{2}$ -(Al $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ and from 5.26 to 8.56 eV for $I^\pm$ -(Al $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ . Most of the band offset of the (Al $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ alloy arises from the discontinuity in the conduction band. Our results are used to explain the available experimental data, and consequences for designing modulation-doped field effect transistors (MODFETs) based on (Al $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ /Ga $_{2}$ O $_{3}$ are discussed.

Band gap and band offset of Ga2​O3​ and (Alx​Ga1−x​)2​O3​ alloys

Abstract

Band gap and band offset of Ga $_{2}$ O $_{3}$ and (Al $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ alloys