Engineering the Photoresponse of InAs Nanowires

Abstract

We report on individual-InAs nanowire optoelectronic devices which can be tailored to exhibit either negative or positive photoconductivity (NPC or PPC). The NPC photoresponse time and magnitude is found to be highly tunable by varying the nanowire diameter under controlled growth conditions. Using hysteresis characterization, we decouple the observed photoexcitation-induced hot electron trapping from conventional electric field-induced trapping to gain a fundamental insight into the interface trap states responsible for NPC. Furthermore, we demonstrate surface passivation without chemical etching which both enhances the field-effect mobility of the nanowires by approximately an order of magnitude and effectively eliminates the hot carrier trapping found to be responsible for NPC, thus restoring an "intrinsic" positive photoresponse. This opens pathways toward engineering semiconductor nanowires for novel optical-memory and photodetector applications.

Review on III-V Semiconductor Single Nanowire-Based Room Temperature Infrared Photodetectors

“…Alternatively, applying an insulating layer and a contacting layer on top of the nanowire, a top-gated FET can be achieved as shown in Figure 2d [11,35]. Such transistor structures have been used for InAs photodetectors to manipulate electron trapping sites formed by the native oxide, leading to tunable positive or negative photoconductivity [11,36,37,80,81]. Although most semiconductors have increased conductivity under photoexcitation (positive photoconductivity (PPC)), Alexander-Webber et al reported an unusual negative photoconductivity (NPC) of InAs nanowire-based phototransistors under visible light illumination as shown in Figure 2b [36].…”

“…Such transistor structures have been used for InAs photodetectors to manipulate electron trapping sites formed by the native oxide, leading to tunable positive or negative photoconductivity [11,36,37,80,81]. Although most semiconductors have increased conductivity under photoexcitation (positive photoconductivity (PPC)), Alexander-Webber et al reported an unusual negative photoconductivity (NPC) of InAs nanowire-based phototransistors under visible light illumination as shown in Figure 2b [36]. This surface photo-gating effect may be explained by the fact [36,80] that the free carriers in the InAs nanowire could be excited into charge trapping sites located in the surface native oxide after the absorption of light with photon energy much higher than the bandgap.…”

“…Although most semiconductors have increased conductivity under photoexcitation (positive photoconductivity (PPC)), Alexander-Webber et al reported an unusual negative photoconductivity (NPC) of InAs nanowire-based phototransistors under visible light illumination as shown in Figure 2b [36]. This surface photo-gating effect may be explained by the fact [36,80] that the free carriers in the InAs nanowire could be excited into charge trapping sites located in the surface native oxide after the absorption of light with photon energy much higher than the bandgap. It was also found that the time-dependent photoresponse of the device at increased gate voltages showed a more obvious and gradually saturated NPC behavior under illumination and increased current after the light was switched off with an optical memory effect [36].…”

“…Researchers have also implemented transistor structures [11,[35][36][37], metal-semiconductor (M-S) or metal-semiconductor-metal (M-S-M) Schottky junctions [38][39][40][41], p-n junctions [42,43], and heterostructures [42][43][44][45][46] in nanowire-based photodetectors to further reduce dark current and enhance I light /I dark ratio for infrared photodetection. In addition, surface passivation [11,36,44] and introduction of the photo-gating effect [36,37,47] have been carried out to manipulate the surface states of the nanowire materials to further enhance their performance. It has also been demonstrated that metal-cluster decoration [11] and nanoantenna structures [48] are capable of localizing and enhancing the spectral selectivity and light absorption of nanowires by coupling of strongly resonant and highly localized plasmonic modes.…”

Grain size control of crystalline III–V semiconductors at ambient conditions using electrochemically mediated growth

“…III-V semiconductors exhibit exceptional (opto)electronic properties, which makes them ideal functional materials in photovoltaics, [1][2][3][4] photoelectrochemistry, [5][6][7] light sensors, [8][9][10] light sources 11 and high speed devices. 12,13 The growth mechanisms of III-V semiconductors in the vapour phase have been extensively studied, [14][15][16] shedding light on the effect of growth parameters on the strain, crystallinity and impurities.…”