Trace Al component in ε-(AlxGa1-x)2O3 alloy films and film-based solar-blind photodetectors

Abstract

ε-(AlxGa1-x)2O3 alloy thin films containing Al fractions of 0, 2.9 at%, and 4.7 at% with ε-Ga2O3 templates were fabricated on (0001) c-sapphire by tin-assisted PLD technique. Sn is a surface-mediated surfactant to stabilize the formation of epsilon phase. XRD reveals that the peak position of ε-(AlxGa1-x)2O3 shifts to a higher diffraction angle and that ε-(AlxGa1-x)2O3 is accompanied by a deterioration of crystal quality when the Al composition increases from 0 to 4.7 at%. With Al content increasing, XPS demonstrates the appearance of more aluminum atoms bound to oxygen atoms and higher oxygen vacancy density in ε-(AlxGa1-x)2O3 films. The optical bandgap for ε-(AlxGa1−x)2O3 thin films with various Al components are 4.97 eV, 5.09 eV and 5.16 eV, respectively. The solar-blind photodetectors were fabricated on ε-(AlxGa1-x)2O3 alloy thin films with various Al fractions. The photo-to-dark current ratio, responsiveness, detectivity and response time (rise time/decay time) for ε-(AlxGa1-x)2O3 (x = 2.9 at%) PDs were 2.7 × 103, 4.2 A/W, 1.23 × 1013 Jones and 2.09 s/0.49 s.