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

Tin oxide (SnO 2 ) is one of the transparent conducting oxide semiconductors that have been widely used in optoelectronic devices. To extend SnO 2 -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.