Properties Of Carbon Nanotube/germanium IR Photodetectors

With the advent of the information age,light detection has become one of the key components of modern science and technology.Infrared photodetector,as an effective conversion device of light signals to electrical signals,is the heart of wide applications in light detection.Semiconductor materials are the basis of infrared photodetectors.Although the technology of semiconductor infrared photodetector has been mature,it still faces problems such as complex preparation processes and scarcity of raw materials.At the same time,the research on the optoelectronic properties of materials at the nanoscale has been promoted by the continuous development of nanotechnology.To this end,according to the"carbon nanomaterial/semiconductor Schottky diode"model,combining the excellent electrical conductivity and light transmittance of carbon nanotube films,the author design an easy-assembly carbon nanotube-Germanium（CNT-Ge）heterojunction photodetector,which composes of carbon nanotube film and germanium with excellent performance,such as short response time,high responsivity and high detectivity.Carbon nanotube films was prepared by chemical vapor deposition method,and the film was characterized and tested.The carbon nanotube film/germanium infrared photodetector is obtained by assembling the germanium sheet and the carbon nanotube film.Compared with multilayer graphene（MLG）/gallium arsenide nanocones（GaAs NCs）infrared photodetectors(response time,responsivity and detectivity are of 72μs,of 1.73m A W^-1and of 1.83×10¹¹cm Hz^1/2W^-1)The ultra-fast light response of CNT/Ge device is 7μs without bias voltage.Moreover,the responsivity and detectivity are of 123 m A W^-1and of 2.90×10¹¹cm Hz^1/2W^-1,respectively.Furthermore,three methods were adopted to optimize the performance of carbon nanotube thin film/germanium infrared photodetectors through introducing functional layer and chemical doping.Atomic layer deposition of alumina was used to improve the performance of carbon nanotube film/germanium infrared photodetector.The responsivity and the detectivity of carbon nanotube film/2 nm alumina/germanium detector achieved 0.212 m A W^-1and 5.1×10¹¹cm Hz^1/2W^-1,respectively.Secondly,a novel spin-coating method of liquid oxidant with variable rotational speed is proposed to improve the performance of the detector.The liquid oxidant was uniformly dispersed on the surface of the detector by the centrifugal action of the homogenizer.The responsivity and detectivity of the carbon nanotube film/germanium detector treated with 0.01 M nitric acid solution reached 311 m A W^-1and 5.8×10¹¹cm Hz^1/2W^-1,respectively.Finally,the optimized method of ozone treatment of carbon nanotube films was applied to improve the performance of carbon nanotube films/germanium infrared photodetectors,the structure of carbon nanotubes is destroyed under the etching action of ozone treatment.However,ozone functionalization occurs in the external carbon nanotube wall,because of the carbon nanotube film has a high degree of defect site.The effect of different ozone treatment time on the performance of the carbon nanotube film/germanium infrared photodetector was studied.The responsivity and detectivity of the carbon nanotube/germanium detector treated with ozone for 30 min were 363 m A W^-1and 7.2×10¹¹cm Hz^1/2W^-1,respectively.The optimization method of gold nanoparticles was used to modify carbon nanotube film by the auhor,and it was applied to improve the performance of carbon nanotube film/germanium infrared photodetector,the responsivity and detectivity of the detectors were increased to 476 m A W^-1and 1.0×10¹²cm Hz^1/2W^-1.With the continuous development of research work,carbon nanotube films/germanium infrared detectors are expected to be applied to military and life.