Annealing effects of Au nanoparticles on the surface-plasmon enhanced p-Si/n-ZnO nanorods heterojunction photodetectors

Abstract

The effects of various annealing temperatures (350-550 C) of Au nanoparticles (NPs) on the surface-plasmon enhanced p-Si/n-ZnO nanorods (NRs) heterojunction photodetectors (HPDs) have been investigated. The photoresponse of the surface-plasmon-mediated HPDs was found to be determined by the extinction band of the Au NPs, the defects of ZnO NRs, and the Schottky-barrier height (SBH) between the Au and ZnO interface. The higher annealing temperature (550 C) causes more defects in ZnO NRs and lowers the ultraviolet (UV) response of the fabricated p-Si/n-ZnO NRs HPDs. The higher annealing temperature also renders a rougher surface in the Au NPs, thereby leading to destructive interference and hence the narrowest extinction band. In contrast, the modest temperature (450 C) results in fewer defects in ZnO NRs, the widest extinction band in Au NPs, and the lowest SBH at the Au/ZnO interface. Such a result enhances the UV-to-visible rejection ratio from 439.6 to 6447 as compared to the HPDs without Au NPs. A band diagram considering the above investigations is illustrated to elucidate the surface plasmon resonance effects on enhancing the UV response. V

Transparent conductor-Si pillars heterojunction photodetector

“…Due to the applied forward-bias, the barrier height is lowered (Fig. 8(d)), 5,6,9,29 resulting in increased dark current. For our ITO/Si heterojunction devices, forward-bias modulation degrades the photo-responses.…”

“…8(e)). 6,17 The SiO x layer between the ITO and the Si effectively hinders the hole-carrier transport from the p-Si to the ITO. 30 However, a reverse bias activates trap-assisted holetunneling in the thin oxide layer.…”

“…[1][2][3][4][5][6] However, the biased operation 2,3,6 readily increases dark current values and, thus, easily decreases the photo-responses, besides the inevitable power dissipation.…”

“…ZnO-based UV photodetectors are usually photo-chemically reactive and showed slow responses. 2,[7][8][9] Nanostructures have attracted intensive interest due to their high aspect ratio; they provide an enlarged light-reactive surface that improves photo-responses 6,8,[10][11][12][13][14] Meanwhile, the difficulty of nanoscale fabrication is still holding back the progress of nanostructured photoelectric devices due to lack of uniform performance or reproducibility.…”

Polarization Enhanced Charge Transfer: Dual-Band GaN-Based Plasmonic Photodetector

“…for CdSe-Au nanorods (NRs) with a very high transient quantum yield (>24%)45 or that proposed by Hwang et al . for ZnO-Au NRs46.…”