Exploration Of Photodetectors Based On SiC Low-dimensional Nanostructures And Their Photodetecting Properties

Silicon carbide (SiC) is a third generation of semiconductormaterial with excellent physical qualities such as wide band gap, highthermal conductivity, high electron saturation drift velocity, high criticalbreakdown field, low intrinsic carrier concentration, strong irradiationresistance and good chemical stability. It is regarded as an ideal materialto make high temperature, high frequency, high pressure resistance,radiation resistance, high power electronic devices, which can becompatible with the mature silicon planar process. It has wideapplications in photocatalysis under harsh conditions, gas sensitivedetection, display device, gas sensor, missile plume detection device andother important fields. SiC low-dimensional nanostructures not only havethe excellent performance of their block structure, but have the uniqueadvantages of low-dimensional nanostructures. They are expected to bring opportunities for research and development of novel and highlyefficient microelectronic devices.In this work, we report the synthesis of SiC NWs via a simplechemical vapor deposition method. By exploring and optimizingthe process parameters, we have got high-quality SiC single-crystallinenanowires. In terms of device design and assembly, a standardphotolithography technique is used to fabricate single-nanowire devices.A simple drip-coating method is used to make photodetectors based onSiC nanowire films and a DEP self-organization processing techniques isused to obtain large-scale ordered NW arrays on rigid/flexible substrate.The results show that the developed photodetector has high sensitivity,fast response, and good repeatability. According to thecomprehensive work of this thesis, the main results are as follows:(1) Single-crystalline SiC NWs were synthesized by a simplechemical vapor deposition method using carbon fibers and white ashesfrom rice hulls as raw materials. The structure characterization analysisresults show that the as-prepared SiC nanowires has a single-crystallinenature and a-cubic phase structure.(2) The single SiC NW-based photodetector has a goodperformance. The photoresponse times, are about0.20s and0.09srespectively, indicating a fast response to illumination. The calculated Riand EQE values of the single SiC NW-based photodetector are as high as 3.3×106A/W and9.7×108%irradiated by420nm light at an appliedvoltage of5.0V, respectively, which indicate the excellent sensitivity ofthe as-fabricated devices. The experiment shows that single SiCNW-based PDs can work properly even at200℃without noticeabledeterioration.(3) Photodetectors based on SiC nanowire films can exhibit theexcellent performances of high sensitivity upon irradiation of420nm,with good repeatability and stability. The photocurrent has a nearly linearrelationship with the optical power density.(4). The NW-array photodetectors on silicon substrates exhibitenhanced optoelectronic performance compared with the single-NWdevices. Flexible photodetectors are fabricated on poly(ethyleneterephthalate)(PET) substrates, showing excellent mechanical flexibilityand stability. It shows enhanced photocurrent and dark current comparedwith the NW-array photodetectors on silicon substrates, which may becaused by poor contact between the nanowires and flexible substrate.