Discovery of New Polymorphs of Gallium Oxides with Particle Swarm Optimization‐Based Structure Searches

Abstract

Gallium oxide (Ga2O3) has attracted significant research interest for next‐generation high‐efficiency power devices because of its unique electronic properties such as ultra‐wide band gap, high breakdown electric field, and large Baliga’s figure of merit. Ga2O3 crystallizes in a series of reported polymorphs including β‐, α‐, ε‐, κ‐, γ‐, and δ‐Ga2O3, the structures of some of which are still in serious controversy. A polymorph structure search study of Ga2O3 is herein performed by combining particle swarm optimization with first‐principles energetic calculations. In addition to producing the predominant experimental known phases of β‐, α‐, and κ‐Ga2O3, two new polymorphs are found with space group P1true¯ and Pmc21 consisting of four‐ and five‐fold coordinated Ga. They show comparable energy with β‐ and α‐Ga2O3 with the energy difference of several meV per atom, and exhibit robust phonon stability. Similarly, the new phases show quite wide band gaps and small electron effective masses by comparing it with other known phases. The Pmc21 phase shows a calculated spontaneous polarization of 0.277 C m−2, close to that of ε/κ‐Ga2O3. The systemic structure searches also establish a structural relationship between ε‐Ga2O3 and κ‐Ga2O3 and how the electronic properties vary with polymorphic phase change.

Highly Active and Selective Sites for Propane Dehydrogenation in Zeolite Ga-BEA

“… The Ga impregnation and subsequent removal of Zn by H 2 reduction did not change the diffraction patterns. Diffraction features corresponding to bulk GaO x and ZnO x species were not detected. , Table and Table S1 compile the physical and chemical properties of Ga/BEA-X catalysts. The properties of Ga/Zn-BEA-X catalysts are presented in Table S2.…”

A Strategic Review on Gallium Oxide Based Deep‐Ultraviolet Photodetectors: Recent Progress and Future Prospects

“…The other phases, although metastable or unstable, have been reported in literature. [80,99] The α-phase is a metastable phase with trigonal lattice which changes to the stable β-phase at temperatures above 400 °C. Other metastable phases include the ε-phase with a hexagonal crystal structure and the cubic γ-phase.…”

Recent progress on the effects of impurities and defects on the properties of Ga2O3

“…The lattice parameters of e-Ga 2 O 3 are a = b = 2.90 Å, c = 9.26 Å, a = b = 901, g = 1201. 90,93 Note that hexagonal e-Ga 2 O 3 has a larger spontaneous polarization (P (e-Ga2O3) = 24.44 mC cm À2 ) compared with GaN. 33,94 Inspired by the previous work on the Al x Ga 1Àx N/GaN heterojunctions, high-density two-dimensional electron gas (2DEG) can be formed at the e-(Al x Ga 1Àx ) 2 O 3 /e-Ga 2 O 3 interface without any intentional doping.…”