Correlation of Pulsed Gas Flow on Si-doped α-Ga₂O₃ Epilayer Grown by Halide Vapor Phase Epitaxy

Abstract

Gallium oxide (Ga2O3) is the one of the ultra-wide-band-gap semiconductor material. The Ga2O3 semiconductor has been studied for use in highly energy efficient devices. Among its phases, the β-phase of Ga2O3 has mainly been researched until recently. However, the α-phase, which has superior properties (e.g., wider band-gap and higher symmetry) has been discussed in the electronic-materials field of late. There are problems that need to be overcome in order for the α-phase to be a suitable electronic material; one of them is the production of high-quality thin films. This article reports the fabrication of a high-quality Si-doped α-Ga2O3 epilayer on α-Al2O3 substrate by halide vapor-phase epitaxy with the controlled pulse flow of each precursor. The α-Ga2O3 epilayer grown with a controlled pulse flow of O2 has a lower full width at half maximum (FWHM; 1306 arcsec) for the 10–14 diffraction compared to the FWHM (2011 arcsec) of the as-grown sample. The pulse-flow mode of introducing Ga and O2 strongly influences the crystal quality of α-Ga2O3. In the O2-control mode, we demonstrated Si-doped α-Ga2O3 epilayers with higher electron mobility up to 51.57 cm2 V−1 s−1 and wider carrier concentrations range of 1017 ∼ 1019 cm−3 by improving the crystal quality.

α-Gallium Oxide Films on Microcavity-Embedded Sapphire Substrates Grown by Mist Chemical Vapor Deposition for High-Breakdown Voltage Schottky Diodes

“…Figure c shows that the largest breakdown voltages of samples E and F were 679 and 532 V, respectively, implying that sample E had a higher breakdown voltage due to the lower density of TDs, which can act as leakage current paths in the α-Ga 2 O 3 films. The breakdown voltages show relatively higher values than other α-Ga 2 O 3 -based diode results, benefiting from the high crystallinity of the α-Ga 2 O 3 templates. ,, It is expected that the performance of the diodes that are based on α-Ga 2 O 3 films on MESS will be boosted through the optimizing fabrication process such as doping , and etching …”

“…However, α-Ga 2 O 3 thin films grown on sapphire substrates suffer from high-density threading dislocations (TDs) and cracks. The film has a high TD density of 10 10 cm –2 due to a large lattice mismatch of 4.8% along the a -axis. , In addition, because α-Ga 2 O 3 has a larger thermal expansion coefficient than α-Al 2 O 3 , a sapphire substrate bends upward during cooling, and cracks form in a film with a thickness of 3 μm or more. , Researchers have tried a variety of techniques for growing high crystalline and crack-free α-Ga 2 O 3 thin films, including the use of buffer layers, , the epitaxial lateral overgrowth (ELO) on patterned sapphire substrates or sapphire substrates with dielectric masks (SiN, SiO 2, , and TiO x , ), and the selective area growth (SAG) on sapphire nanomembranes . Son et al reported the enhanced crystallinity of α-Ga 2 O 3 thin films via the ELO on conical frustum-patterned sapphire substrates with halide vapor phase epitaxy (HVPE).…”

Realization of Conductive n‐Type Doped α‐Ga2O3 on m‐Plane Sapphire Grown by a Two‐Step Pulsed Laser Deposition Process

“…[14,[16][17][18] However, up to now, no reports on doped and conductive α-Ga 2 O 3 deposited by PLD exist to the best knowledge of the authors.Typically, a low dislocation density in α-Ga 2 O 3 thin films on sapphire is required to achieve high electron mobilities. [19] Different approaches have been reported to decrease the dislocation density and therewith improve the structural and…”

“…Typically, a low dislocation density in α-Ga 2 O 3 thin films on sapphire is required to achieve high electron mobilities. [19] Different approaches have been reported to decrease the dislocation density and therewith improve the structural and…”

“…Using m-plane sapphire substrates, electron mobilities as high as 51 and 65 cm 2 V À1 s À1 have been reported for Si-doped and Sn-doped α-Ga 2 O 3 thin films, respectively. [19,28] The electron mobility of α-Ga 2 O 3 thin films grown on c-plane sapphire is significantly lower. [29] Following the approach presented by Akaiwa et al in 2020 for mist-CVD, [28] we present undoped and doped α-Ga 2 O 3 thin films deposited by PLD on m-plane sapphire substrates.…”