Characterization of band offset in α-(AlxGa1-x)2O3/ α-Ga2O3 heterostructures
Gallium Oxide is a promising material for power device applications. We focused on corundum structured gallium oxide (α-Ga<sub>2</sub>O<sub>3</sub>) and α-(Al<sub>x</sub>Ga<sub>1-x</sub>)<sub>2</sub>O<sub>3</sub>/ α-Ga<sub>2</sub>O<sub>3</sub> heterostructure devices. We prepared α-(Al<sub>x</sub>Ga<sub>1-x</sub>)<sub>2</sub>O<sub>3</sub> alloy and these laminate structures on c-plane sapphire substrates. The band offset of the α-Ga<sub>2</sub>O<sub>3</sub>/α-(Al<sub>x</sub>Ga<sub>1-x</sub>)<sub>2</sub>O<sub>3</sub> heterostructure was measured by X-ray photoelectron spectroscopy (XPS). The band alignment was estimated to be type I with very narrow valence-band offset energy.
Band Gap and Band Offset of 
Ga2O3
 and 
(AlxGa1−x)2O3
 Alloys
The band gaps and band offsets of the transparent conducting oxides Ga${}_{2}$O${}_{3}$ and (Al${}_{x}$Ga${}_{1\ensuremath{-}x}$)${}_{2}$O${}_{3}$ are key parameters in the design of next-generation high-power transistors and solar-blind ultraviolet photodetectors and solar cells. Based on first-principles calculations, the authors determine the mixing enthalpies, band-gap bowing, and band offsets of (Al${}_{x}$Ga${}_{1\ensuremath{-}x}$)${}_{2}$O${}_{3}$ alloys. The band gap can be tuned across a wide range by changing Al composition, adding great flexibility in device design, while the offset arises mostly from discontinuity in the conduction band.
A concept of general monotonicity and applications
In this paper we investigate properties of the general monotone sequences and functions, a generalization of monotone sequences and functions as well as of those of bounded variation. Some applications to various problems of analysis are given. © 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim