InGaN metal-semiconductor-metal photodetectors with triethylgallium precursor and unactivated Mg-doped GaN cap layers

Abstract

InGaN epitaxial films grown by metalorganic chemical vapor deposition using trimethylgallium and triethylgallium as precursors exhibited different optical and electrical properties. The films were characterized by x-ray diffraction, photoluminescence, secondary ion mass spectroscopy, and atomic force microscopy. Impacts of unactivated Mg-doped GaN in situ grown cap layers on InGaN and GaN films were further investigated. Current-voltage and spectral response measurements combined with Hall-effect measurement and analytical modeling have been used to assess possible current transport mechanisms of reverse dark and photo current flow in metal-semiconductor-metal photodetectors fabricated from InGaN and GaN. Unlike the dominant thermionic emission, which can be blocked by higher and thicker potential barrier in GaN, the trap-assisted tunneling is more pronounced in InGaN. The passivation effect on high density surface states in InGaN is proposed to explain the improved device performances after the incorporation of Mg-doped GaN.