Crystalline trigonal selenium flakes grown by vapor deposition and its photodetector application

Abstract

In this study, we discuss the growth of crystalline t-Se flakes by physical vapor deposition and fabrication of micro photodiodes (μPDs). Direct growth of crystalline t-Se flakes on a c-plane sapphire substrate was confirmed by X-ray diffraction, Raman spectroscopy and optical absorption spectroscopy. Schottky and Ohmic contacts between t-Se flakes and the electrode were realized using Ti and Au, respectively. For Ohmic characteristics, anomalous transport on an anisotropic crystal structure was observed. The t-Se based Schottky barrier diode (SBD) consisting of Ti and Au electrodes with low reverse saturation current was fabricated. The ideality factor n and the Schottky barrier height ΦB were estimated to be approximately 1.4 and 0.66 eV, respectively. A high responsivity of 0.717 A/W and quantum efficiency of 137% were observed at Vbias = −3 V under irradiation of various powers of red-LED (650 nm), indicating the good performance of μPD for monitoring the red and visible light color.