Photodetector Arrays Based on MBE-Grown GaSe/Graphene Heterostructure

A selective area growth of hexagonal GaSe on prepatterned graphene substrate and fabrication of a photodetector array is reported. The GaSe film is grown on the graphene substrates using a molecular beam epitaxy system and characterized for structural and morphological properties using X-ray diffraction, Raman, and atomic force microscopy techniques. Preliminary observations indicate the growth of hexagonal GaSe layers along (001) direction on graphene film under certain optimum growth conditions. Subsequently, GaSe-based Schottky diode photodetectors are fabricated in a single-element and 16 x 16 crossbar array geometries. Current-voltage characteristics of the diodes show a rectifying behavior with a turn-on voltage and a low leakage current of approximate to 2 V and approximate to 20 nA, respectively. Photoresponse characteristics of the diode are investigated by measuring wavelength-dependent spectral response and temporal photocurrent response under illumination of different lights, including 532 nm laser and white light, with varied incident intensities. The spectral responsivity of the detector is found to be as high as 98 A W-1 at a wavelength of 500 nm with a turning-on profile corresponding to the band edge of GaSe. The photo mapping capability of the detector array is also demonstrated in this report.