The inset shows

the SEM image of FET based on a single InSb nanowire. (b) I ds versus V gs characteristic curve at V ds = 5 V. The carrier concentration of 3.6 × 1017 cm−3 and mobility of 215.25 cm2 V−1 s−1 are obtained. To understand the photoresponse characteristics of the InSb nanowires, a single InSb nanowire was connected with the Pt Schottky contact electrodes to fabricate a nanodevice based on the M-S-M structure and measured using a Keithley 4200 system. The Pt-InSb-Pt structure constitutes a typical M-S-M photodetector. The photocurrent of the InSb nanowire is dependent on light intensity. Figure 3a shows the I-V curves of the InSb nanowire irradiated with a wavelength of 5.5 μm at different light intensities. The symmetric rectifying I-V curves exhibited two characteristics of back-to-back Schottky contacts at the two ends of the InSb nanowire. Furthermore, it shows that the conductance increases from 618.9 this website nS in a dark state to 3320 IWR-1 chemical structure nS in a state of light intensity of 508 mW cm-2. The simultaneous increase of the photocurrent with the light intensity

is consistent with the carrier generation efficiency being proportional to the absorbed photon flux. Figure 3b shows that the photocurrent dependence on light intensity can match a simple power law: I = AP θ , where A is a constant for a certain wavelength, and the exponent θ determines the response of the photocurrent to the light intensity. Fitting the curve yields θ = 0.2. The non-unity and a small HSP90 θ suggest a complex process of electron–hole generation, recombination, and trapping [36]. Furthermore, the result implies the existence of numerous defects for the InSb nanowire. The existence of defects may derive from the surface vacancy, as reported in our previous work [25]. The same phenomenon had been observed in studies on CdS nanobelts [37] and CdTe nanoribbons [38]. In addition, the quantum efficiency (QE) is a critical parameter in evaluating a photosensitive device, which relates to the number of electron–hole pairs excited

by one absorbed photon, and can be used to determine the efficiency of electron transport and collection by electrodes. A high QE corresponds to a high sensitivity. The QE can be expressed by the following equations [39]: (3) (4) where N e is the number of electrons collected in a unit time, N p is the number of photons absorbed in a unit time, τ is the carrier lifetime, t tran is the transit time between the electrodes, and λ is the wavelength of irradiated light. R λ is the spectral responsivity, defined as the photocurrent generated per unit of power of the incident light on effective areas. ΔI is the difference between a photocurrent and a dark current, P is the incident light intensity, and S is the area of the nanowire. For the incident light of 5.5 μm at 0.49 mW cm−2, R λ is 8.4 × 104 A W−1. This corresponds to a QE of 1.96 × 106%.