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.
Evolution of corundum-structured III-oxide semiconductors: Growth, properties, and devices
The recent progress and development of corundum-structured III-oxide semiconductors are reviewed. They allow bandgap engineering from 3.7 to ∼9 eV and function engineering, leading to highly durable electronic devices and deep ultraviolet optical devices as well as multifunctional devices. Mist chemical vapor deposition can be a simple and safe growth technology and is advantageous for reducing energy and cost for the growth. This is favorable for the wide commercial use of devices at low cost. The III-oxide semiconductors are promising candidates for new devices contributing to sustainable social, economic, and technological development for the future.
Preparation and Properties of Hydrothermally Stable γ‐Alumina‐Based Composite Mesoporous Membranes
We report here on our thermal and hydrothermal investigations comparing mesoporous γ-Al2O3 membrane with single and double dopant membranes prepared by the sol–gel method. Improvements in the hydrothermal stability of mesoporous γ-Al2O3 by transition (Ga3+) or rare-earth (La3+) cations are discussed, along with the effectiveness of double dopant (Ga3+–La3+). The amounts of Ga2O3 oxide used varied between 0.0 and 30 mol% and those of La2O3 between 6 and 15 mol%. The thermal and hydrothermal (up to 75% steam) stability of nine types of membranes fabricated on an asymmetric porous α-Al2O3 support by means of a dip-coating process was characterized by H2 gas permeation at 500°C. By conducting tests with wide variations in dopant concentrations, material characterizations, and gas permeance performance, we have been able to optimize the key parameters for hydrothermally stable systems.