Phase Transition and Bandgap Engineering of MgSnO Thin Films for Solar-Blind Ultraviolet Photodetector Applications

Tin oxide (SnO2) is one of the transparent conducting oxide semiconductors that have been widely used in optoelectronic devices. To extend SnO2-based optoelectronic applications into the deep ultraviolet solar-blind wavelength range, in this research, MgSnO alloy thin films were grown on c-sapphire using plasma-assisted molecular beam epitaxy. As Mg composition is between 0 and ∼24.4 at. %, MgSnO films exhibit rutile structure. The lattice constants increase as the Mg composition increases. MgSnO films become amorphous as Mg composition exceeds 24.4 at. % and eventually become rock-salt structures as Mg composition exceeds 45.9 at. %. The optical bandgap of MgSnO increases with the increase in Mg composition. Metal–semiconductor–metal (MSM) photodetector devices were fabricated and characterized. When Mg composition increases, both the dark current and photocurrent of the devices decrease. High responsivities were observed for all MgSnO MSM devices

Investigation of Phase Transition and Ultrawide Band Gap Engineering in MgGaO Semiconductor Thin Films

Magnesium gallium oxide (MgGaO) ternary alloys with band gap energy larger than ∼5.0 eV can provide opportunities for optoelectronics in the deep ultraviolet spectral range and power electronics with extremely high critical field strength. It is important to grow high-quality MgGaO alloys with varied Mg compositions and understand their structural and optical properties. From this perspective, 20 MgGaO samples with Mg atomic percentages from 0 to 100% were grown by using oxygen plasma-assisted molecular beam epitaxy. Band gap tuning from 5.03 to 5.89 eV was achieved for the ternary alloys, and all samples had a transmittance of over ∼90% in the visible spectral range. The lattice structures were confirmed to transform from the β phase in Ga-rich materials to the β and rocksalt mixture phase in high-Ga high-Mg alloys and to the pure rocksalt phase in Mg-rich alloys. How lattice parameters change with the increase of Mg atom % and the epitaxy relationship between MgGaO films and c-sapphire substrates were revealed