Spectrally distinctive and highly responsive self-powered MoS₂/GaN-nano/Si based photodetector

Efficient photodetectors require high and fast photo-response as well as low power consumption. In the present work, we have demonstrated MoS₂/GaN nanorods/Si based self-powered and most importantly, spectrally distinctive photodetector. GaN nanorods were grown on Si (111) by Volmer-Weber type growth conditions using plasma-assisted molecular beam epitaxy, followed by growth of MoS₂ by pulsed laser deposition. HRTEM analysis shows MoS₂ has been incorporated on the top and sides of the nanorods, as well as in between them on Si. The device with top-bottom electrodes shows a maximum responsivity of 10.67 A/W at 900 nm in zero bias condition. The response and the recovery times have been estimated to be 30.9 and 33.9 μs, respectively. The spectral response studies also revealed that in the range of infrared wavelength (1000 - 1050 nm), there is an inversion (positive to negative) in the photocurrent. A mechanism based on illumination modulated activation of barriers, and the interaction of MoS₂ with GaN and Si has been discussed to explain the observed phenomenon of polarity inversion.