Band Gap and Band Offset of Ga2O3 and (AlxGa<

Abstract

Ga2O3 and (AlxGa1−x)2O3 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 Ga2O3 and (AlxGa1−x)2O3, 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 (AlxGa1−x)2O3 alloys in the monoclinic (β) and corundum (α) phases. We find the formation enthlapies of (AlxGa1−x)2O3 alloys are significantly lower than of (InxGa1−x)2O3, and that (AlxGa1−x)2O3 with x=0.5 can be considered as an ordered compound AlGaO3 in the monoclinic phase, with Al occupying the octahedral sites and Ga occupying the tetrahedral sites. The band gaps of the alloys range from 4.69 to 7.03 eV for β-(AlxGa1−x)2O3 and from 5.26 to 8.56 eV for α-(AlxGa1−x)2O3. Most of the band offset of the (AlxGa1−x)2O3 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 (AlxGa1−x)2O3/Ga2O3 are discussed.

Band alignment at surfaces and heterointerfaces ofAl2O3,Ga2O3,Hinuma1, Gake2, Oba3 2019Phys. Rev. Materials384210View full textAdd to dashboardCite

“…Peelaers et al estimated the valence-band offsets at corundum (1010) and β-gallia (010) Al 2 O 3 /Ga 2 O 3 interfaces to be −0.24 and 0.37 eV, respectively, where the negative (positive) value indicates the VBM of Al 2 O 3 is lower (higher) than that of Ga 2 O 3 , along with the band positions of (Al x Ga 1−x ) 2 O 3 alloys via IP difference calculations using the HSE hybrid functional with a tuned Fock-exchange mixing value of 0.32 [31]. Wang et al gave values of −0.11 and 0.33 eV, respectively, for these two interfaces via explicit interface calculations using HSE with 0.32 mixing [30]. The discrepancies between our results and Refs.…”

“…The discrepancies between our results and Refs. [30,31] for β-gallia (010) Al 2 O 3 /Ga 2 O 3 may be attributed to the difference in the functional form and parameter values that yields a band-gap difference of ∼0.1 eV for Al 2 O 3 and the derivation procedure for IP differences and interfacial natural band offsets: the Fock-exchange mixing values are 0.33 and 0.25 for Al 2 O 3 and Ga 2 O 3 in the β-gallia structure, respectively, in our study using a dd full-range hybrid functional, while a range-separated HSE functional was used in Refs. [30,31] with the aforementioned Fock-exchange mixing value of 0.32 and a screening parameter.…”

“…In particular, α-Ga 2 O 3 has been studied as a wide-gap semiconductor. Examples are n-type doping with Sn [27] in a manner similar to the β phase [28] and alloying with isostructural α-Al 2 O 3 for band-gap engineering [29][30][31]. In 2 O 3 typically crystalizes in the bixbyite structure.…”

First-principles study of self-trapped holes and acceptor impurities in Ga2O3 polymorphs

“…Experimental and theoretical studies on phases other than the β phase are limited. Among the metastable phases, α-Ga 2 O 3 has been extensively studied [33][34][35] and its alloy with α-Al 2 O 3 has attracted attention in band-gap engineering [36,37]. In addition, doping of α-Ga 2 O 3 with Sn leads to high n-type conductivity [38], as in the case of β-Ga 2 O 3 [2,9].…”

Prediction of the Abnormal Properties in Monolayer α‐AlxGa2−xO3

“…The optical and electronic properties of Ga 2 O 3 can be effectively modified by different dopants. [ 12–14 ] Al is an important dopant for 3D Ga 2 O 3 , and the Al x Ga 2− x O 3 alloys have been widely studied to achieve the carrier confinement, increase the bandgap, or modify the lattice parameters. [ 15 ] What is more, α‐Al 2 O 3 has a larger bandgap, which can be a gate dielectric to efficiently suppress the gate leakage of devices.…”