| In recent years,one-dimensional semiconductor nanowires(NWs)have been widely applied in photodetectors at room temperature and realized with excellent optoelectronic characteristics,such as ultrahigh intrinsic photoconductive gain,multi-array limiting effect,and subwavelength size effect,due to their small size,large surface-to-volume ratio,high carrier mobility,and tunable light absorption.However,defect-induced intrinsic carriers and surface trapped charges from their rich surface state and high unintentional doping density at certain level result in appreciable dark currents,thus lower the ratio of light to dark current and the detectivity,limiting the detection performance of the photodetectors.Here,one-dimensional semiconductor NWs,such as InP,CdS,SnSe,and SnS NWs are synthesized by a chemical vapor deposition(CVD)method,and photodetectors based on these NWs are fabricated successfully.In this paper,the controllable fabrication of one-dimensional nanowires,the suppression of the dark current and the improvement of the optoelectronic performance of the device are systematically explored and studied.The main contents can be summarized as follows:1.Controllable synthesis of one-dimensional indium phosphide(InP)NWs and the fabrication and research of the photodetector based on single InP NW.The InP NWs are synthesized by CVD method,and single InP NW back-gated field-effect transistors(FETs)are fabricated.Moreover,the electrical and optoelectronic properties of the device are measured at room temperature.The device exhibits a good gate regulation,a high Ion//Ioff ratio of>106,and the carrler field-effect mobility is?67.9 cm2 V-1 s-1.However,the large dark current limits the performance of the NW photodetector.To suppress the dark current,the ferroelectric-enhanced side-gated single InP NW visible-near infrared photodetectors are fabricated by combining ferroelectric materials and NWs for the first time.The intrinsic carriers in the NW channel can be fully depleted by the ultrahigh electrostatic field from polarization of P(VDF-TrFE)ferroelectric polymer.In this scenario,the dark current is significantly reduced and thus the sensitivity of the photodetector is increased even when the gate voltage is removed.While after being depleted,Idark is reduced to?8 × 10-12 A,leading to a much high ratio of IPh/Idark?105 is obtained,the detectivity of the fully depleted device is?500 times larger than that of the not depleted device.The single InP NW photodetector exhibits high-photoconductive gain of 4.2 × 105)responsivity of 2.8 × 105 A W-1 and detectivity of 9.1 × 1015 Jones at a low power density of 0.07 mW cm-2 for ? = 830 nm.The response time,i.e.,the rise time ?r,and the fall time ?f of the detector are about 29.1 and 139.6 ms,respectively.Our work demonstrates a new approach to fabricate controllable,full-depleted,high-performance,and low power consumption NW photodetector.This can inspire novel device structure design of high performance optoelectronic devices based on semiconductor NWs.2.Controllable synthesis of one-dimensional cadmium sulfide(CdS)NWs and the fabrication and research of the CdS NW photodetector.The CdS NWs are synthesized by CVD method,and the electrical and optoelectronic properties of single CdS NW back-gated FET are measured at room temperature.The device exhibits a high Ion/Ioff ratio of>107,and the field-effect mobility is?112 cm2 V-1 s-1 The ferroelectric side-gated single CdS NW ultraviolet-visible photodetectors are fabricated.With the ultrahigh electrostatic field from polarization of ferroelectric polymer,the depletion of the intrinsic carriers in the CdS NW channel is achieved,which significantly reduces the dark current of the photodetector even after the gate voltage is removed.Noise characteristics and noise equivalent power(NEP)of the depleted CdS NW photodetectors are also measured and analyzed.The low frequency noise current power of the device reaches as low as 4.6 × 10-28 A2 at Vds = 1 V.The spatially resolved scanning photocurrent mapping across the device shows strong photocurrent signals near the metal contacts.The single CdS NW UV photodetector exhibits high photoconductive gain of 8.6 × 105,responsivity of 2.6 × 105 A W-1 and detectivity of 2.3 × 1016 Jones at a low power density of 0.01 mW cm-2 for ? = 375 nm.The device demonstrates ultrahigh photoconductive gain of 1.2 x 107,responsivity of 5.2 × 106 A W-1 and detectivity up to 1.7 x 1018 Jones at a low power density of 0.003 mW cm 2 for ? = 520 nm.The detectivity show better performances compared with those reported traditional detectors based on CdS nanostructure.Additionally,the device also shows the advantages of low power consumption,fast-response,and the detection of weak signals and so on.These results demonstrate CdS NW devices will have a broad application,such as controllable,high-performance,low power consumption and weak signal detection.3.Controllable synthesis of one-dimensional Tin selenide(SnSe)and Tin sulfide(SnS)NWs and the fabrication and research of the photodetector based on these NWs.The p-type SnSe and SnS NWs are synthesized by CVD method.Single SnSe and SnS NW photodetectors are fabricated for the first time,and the electrical and optoelectronic properties of these devices are measured at room temperature.The two NW devices exhibit typical p-type semiconductor characteristics,and the hole mobility are about 5.6 and 0.5 cm2 V-1 s-1,respectively.When the bias voltage is 3 V and at a low power density of 0.05 mW cm-2 for ? = 830 nm,the single SnSe NW photodetector exhibits high-photoconductive gain of 1.5 × 104,responsivity of 0.0×104 A W-1 and detectivity of 3.3 × 1012 Jones,the rise time and fall time are about 460 and 520 ?s,respectively.The single SnS NW photodetector exhibits high-photoconductive gain of 2.8 × 104,responsivity of 1.6x 104 A W-1 and detectivity of 2.4 × 1012 Jones,the rise time and fall time are about 1.2 and 15.1 ms,respectively.In addition,the two NW devices show good spectral response characteristics from visible to near infrared,which can achieve high-performance wide spectrum detection.The results show that the p-type SnSe and SnS NWs have a broad application in high-performance photodetectors and other optoelectronic devices,such as high sensitivity,fast-response and wide spectrum detection. |
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