Band alignment at surfaces and heterointerfaces ofAl2O3,Ga2O3,

Abstract

The band alignments at nonpolar surfaces and heterointerfaces of Al 2 O 3 , Ga 2 O 3 , and In 2 O 3 polymorphs, and three related group-III oxides, namely, Sc 2 O 3 , Y 2 O 3 , and La 2 O 3 , are investigated by using first-principles calculations. A non-self-consistent dielectric-dependent hybrid functional approach is adopted on top of semilocal density-functional calculations by using the Perdew-Burke-Ernzerhof functional tuned for solids (PBEsol) to accelerate the band alignment evaluation that involves surface and interface calculations. Among the five crystal structures considered, namely, corundum, β-gallia, κ-alumina, bixbyite (C-type rare earth), and A-type rare earth, the lowest energy phases are corundum, β-gallia, A-type rare earth, and bixbyite for Al 2 O 3 , Ga 2 O 3 , La 2 O 3 , and the others, respectively, within PBEsol calculations. The ionization potential typically decreases in the order Al 2 O 3 , Ga 2 O 3 , In 2 O 3 , Sc 2 O 3 , Y 2 O 3 , and La 2 O 3 within the same crystal structure and surface termination. This tendency is enhanced by the atomic relaxation-induced surface dipoles, where smaller cations tend to relax toward the bulk side compared to O ions, while larger cations tend to relax toward the vacuum side. The ionization potential and electron affinity differences at unrelaxed surfaces are good indicators of the interfacial valence-and conduction-band offsets, respectively, for Al 2 O 3 /Ga 2 O 3 with a relatively small mismatch in the lattice parameters of the two phases.

Machine learning models for predicting the dielectric constants of oxides based on high-throughput first-principles calculations

“…II B). Such tendencies have also been found for prototypical binary oxides [55,56] and semiconductors [16]. The calculated ε ion values deviate more from the experimental values, in particular, ε ion of SrTiO 3 is only 13% of the experimental value at room temperature.…”

Study of Ti contacts to corundum α-Ga2O3

“…This is generally explained using the Schottky-Mott model, since the work-function for Ti of 4.33 eV and the electron affinity for β-Ga 2 O 3 of 4.00 eV [23] result in a low Schottky barrier height-although other factors have been found to play a role, as acknowledged in the Introduction. In the case of α-Ga 2 O 3 , the electron affinity has been predicted at 3.62 eV [24], which implies that a similar ohmic behaviour could be expected.…”

Why In2O3 Can Make 0.7 nm Atomic Layer Thin Transistors

“…Fermi-level pinning concept is extremely important in semiconductor materials and device development and various models were developed spanning several decades. [13][14][15][16][17][18][19][20][21][22][23][24]26,27 Since the physics and chemistry of interfaces are very complex, there are no comprehensive models for both metal/semiconductor and semiconductor/dielectric interfaces. The charge neutrality level (CNL) model is widely applied to describe metal/semiconductor interface.…”

“…Why all of sudden can we scale the 3D semiconductor channel down to an atomic layer thinness of 0.7–1.5 nm, comparable to the thickness of a monolayer or bilayer of 2D van der Waals materials and far thinner than those limits for conventional 3D semiconductors such as Si and GaAs? The Fermi-level pinning concept is extremely important in semiconductor materials and device development and various models were developed spanning several decades. − ,, Because the physics and chemistry of interfaces are very complex, there are no comprehensive models for both metal/semiconductor and semiconductor/dielectric interfaces. The charge neutrality level (CNL) model is widely applied to describe the metal/semiconductor interface .…”