Lasers, Optics & Photonics

Biography

Biography: Hehai Fang

Abstract

Indium arsenide nanowires (InAs NWs), have been widely researched in recent years together with other III-V semiconductor NWs like InP, GaN, InSb etc. With a high mobility and a direct narrow bandgap (approximately 0.35eV), InAs NWs seem to be more appropriate for applications of high-speed electronic components and broad-spectrum detection media. Photodetectors based on single InAs NW and NW arrays have been successfully fabricated and exhibit a good photoresponse. Research has identified two diff erent photodetection mechanisms for single InAs NW photodetector, which are positive photoresponse (PPR) and negative photoresponse (NPR) respectively. Th e diff erence between these two mechanisms is that the latter is a phenomenon induced by surface states similar to a photo-gating layer (PGL) trapping hot electrons and seems to work only when the energy of an incident photon is much higher than the bandgap of InAs. For NPR, an ultrahigh photoconductive gain of -105 and a response time of less than 5ms have been achieved. While for PPR, the responsivity and detectivity reach 5.3×103A/W and 2.6×1011 Jones, which is also a high performance. However, most reported work about InAs NW-based photodetectors is limited to the visible waveband. Although some work shows the certain response for near-infrared light, the problems of large dark current and a small light on/off ratio are unsolved, thus signifi cantly restricting the detectivity. Here in this work, a novel “visible light-assisted dark-current suppressing method” is proposed for the fi rst time to reduce the dark current and enhance the infrared photodetection of single InAs nanowire photodetectors. Th is method eff ectively increases the barrier height of the metal-semiconductor contact, thus signifi cantly make the device a Metal-Semiconductor-Metal (MSM) photodiode. Th ese MSM photodiodes demonstrate broadband detection from less than 1 μm to more than 3μm and a fast response of tens of microseconds. A high detectivity of ~1012 Jones has been achieved for the wavelength of 2000nm at a low bias voltage of 0.1V with the corresponding responsivity of as much as 40A/W. Even for the incident wavelength of 3113nm, a detectivity of ~1010 Jones and a responsivity of 0.6A/W have been obtained. Our work has achieved an extended detection waveband for single InAs NW photodetector from visible and near-infrared to mid-infrared. Th e excellent performance for infrared detection demonstrated the great potential of narrow bandgap NWs for future infrared optoelectronic applications.