Size-Dependent Phase Transition in Ultrathin Ga₂O₃ Nanowires

Abstract

Gallium oxide (Ga 2 O 3 ) has attracted extensive attention as a potential candidate for low-dimensional metal-oxide-semiconductor field-effect transistors (MOSFETs) due to its wide bandgap, controllable doping, and low cost. The structural stability of nanoscale Ga 2 O 3 is the key parameter for designing and constructing a MOSFET, which however remains unexplored. Using in situ transmission electron microscopy, we reveal the size-dependent phase transition of sub-2 nm Ga 2 O 3 nanowires. Based on theoretical calculations, the transformation pathways from the initial monoclinic β-phase to an intermediate cubic γphase and then back to the β-phase have been mapped and identified as a sequence of Ga cation migrations. Our results provide fundamental insights into the Ga 2 O 3 phase stability within the nanoscale, which is crucial for advancing the miniaturization, light weight, and integration of wide-bandgap semiconductor devices.

Stabilizing cubic γ-Ga2O3:Cr3+ spinel nanocrystals by size confinement into mesoporous silica nanoreactor channels

“…The stabilization of the β-Ga 2 O 3 phase for a size smaller than 4.2 nm confirms the results reported by Fang et al 58 and it could be explained considering that the kinetic barriers that need to be overcome to stabilize different polymorphs can be strongly altered by stress and strain, promoting or hindering the stabilization of metastable polymorphs. The same effect of size dependence stabilization of the γ- and β-phase was also recently demonstrated for ultrathin Ga 2 O 3 nanowires by Wang et al , 59 suggesting that positive or negative strains could inhibit the phase transition to the γ-phase at very small sizes. For sizes larger than about 22 nm, the β-Ga 2 O 3 polymorph is again the more thermodynamically favored.…”

In situ atomic-resolution study of transformations in double polymorph γ/β-Ga2O3 structures

“…Consequently, there could be potential discrepancies between the in situ and ex situ observations. In this sense, J. Wang et al 39 showed experimentally and by first-principles calculations that similar transitions occur in Ga 2 O 3 nanowires. From their results, the calculated surface energy of {600}β is smaller than that of {400}γ.…”

“…Consequently, there could be potential discrepancies between the in situ and ex situ observations. In this sense, J. Wang et al 39 showed experimentally and by first-principles calculations that similar transitions occur in Ga 2 O 3 nanowires. From their results, the calculated surface energy of {600}b is smaller than that of {400}g. Considering that a TEM-lamella has a higher surface area/volume ratio than a bulk sample, the observed transition in this work could be influenced by the reduction of the surface energy.…”

A Reliability Investigation of VDMOS Transistors: Performance and Degradation Caused by Bias Temperature Stress

“…Over the past few years, field-effect transistors (FET) have experienced expansion, and an increasing number of authors are conducting research on their reliability. There has been significant research conducted both domestically and internationally on electrospinning technology and its applications in the field of FETs based on metal oxide nanowires [7][8][9][10]. Modern materials are used for both NMOS and PMOS transistors, and nanowire MOSFETs are being developed for various applications, which has spurred the realization of numerous experiments and the characterization of these components.…”