Ga ₂Se ₃ Defect Semiconductors: The Study of Direct Band Edge and Optical Properties

Abstract

Direct band edge is a crucial factor for a functional chalcogenide to be applied in luminescence devices, photodetectors, and solar-energy devices. In this work, the room-temperature band-edge emission of III–VI Ga ₂Se ₃ has been first observed by micro-photoluminescence (μPL) measurement. The emission peak is at 1.85 eV, which matches well with the band-edge transition that is measured by micro-thermoreflectance (μTR) and micro-transmittance (μTransmittance) for verification of the direct band edge of Ga ₂Se ₃. The temperature-dependent μTR spectra of Ga ₂Se ₃ show a general semiconductor behavior with its temperature-energy shift following Varshni-type variation. With the well-evident direct band edge, the peak responsivities of photovoltaic response (∼6.2 mV/μW) and photocurrent (∼2.25 μA/μW at f = 30 Hz) of defect zincblende Ga ₂Se ₃ can be, respectively, detected at ∼2.22 and ∼1.92 eV from a Cu/Ga ₂Se ₃ Schottky solar cell and a Ga ₂Se ₃ photoconductor. On the basis of experimental analysis, the optical band edge and photoresponsivity properties of a III–VI Ga ₂Se ₃ defect semiconductor are thus realized.