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Silicon Nanowires with Controllable Doping and Its Applications as Photodetectors Based on Schottky Diode

Author: MaYuanMing
Tutor: XuGaoBin
School: Hefei University of Technology
Course: Microelectronics and Solid State Electronics
Keywords: silicon nanowires thermal evaporation chemical vapor deposition doping Schottky junction photodetector
CLC: TN311.7
Type: Master's thesis
Year: 2012
Downloads: 8
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Abstract


As an important semiconductor, silicon has very important applications in many fields, such as in field-effect-transistors (FETs), light-emitting diodes, solar cells and chemical sensors and so on. Due to their unique properties, such as quantum size effect, surface effect and large surface to volume ratio, nano-structured materials have many characteristics which are different from bulk or thin-film materials. Nano-devices based on nano-structured materials usually exhibit better performances than nano-devices based on bulk or thin-film materials, and demonstrate some properties that nano-devices based on bulk or thin-film materials do not have.Many methods have been developed to synthesis silicon nanowires (Si NWs) and each method has its own predominance as well as application field. Recently, the studies of the synthesis, doping and application on Si NWs remain the top research point.In this paper, intrinsic Si NWs employed in this study were synthesized by using thermal evaporation of SiO method. The as-synthesized Si NWs were characterized by scanning electron microscope(SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). Controllable p-type doped Si NWs was first accomplished by using B2O3as the boron dopant through tuned diffusion temperature. In addition, the n-type and p-type Si NWs were also synthesized using in situ phosphorus and boron doping via chemistry vapor deposition(CVD) method, respectively. Meanwhile, the back-gate FETs were constructed on a single n-type and p-type Si NWs, respectively. The electrical properties were detailedly investigated on the nano-FETs. Furthermore, the Ti/p-Si NW Schottky diodes were fabricated on individual B doped NWs, and the optoelectronic characterization of the devices were performed. The main achievements obtained were listed as follows:1. Large number of intrinsic Si NWs were successfully synthesized using thermal evaporation of SiO method. The morphology and structure characterization exhibited that the synthesized Si NWs possessed unique appearance and well single crystal structure. Electrical tests and the changes in electrical signals can proved that it is workable to doping intrinsic Si NWs by using diffusing B2O3into Si NWs as boron source and we can dominate the doping level via controlling the temperature of doping.2. The in suit phosphorus and boron doped Si NWs were successfully synthesized by using PH5and BH3as P and B dopant via a CVD method, respectively. Further electrical characterization on back-gate FETs constructed on doped Si NWs indicated the P and B doped Si NWs possessed the n-type and p-type semiconductor properties, respectively. The electron and hole concentration up to1.0×1016cm-3and2.1×1017cm-3, respectively.3. The Ti/p-Si NW Schottky diodes were fabricated on single p-type B doped NWs by using Au and Ti as Ohmic contact and Schottky contact electrodes, respectively. The device exhibited good rectification behavior, ideal factor (n)～2.0and schottky barrier height～0.55eV. In addition, the device demonstrated notable, stable and sensitive to white light at negative bias. The responsivity (R) and gain (G) were estimated to be40AW-1and100, respectively, which are larger than the values of traditional devices.The synthesized n-and p-type Si NWs provide a potential way to fabricated high performance nano-electrical devices and nano-optoelectronic devices. Our results demonstrate the great potential of the Ti/p-Si NW Schottky diodes as high performance photodetectors.

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CLC: > Industrial Technology > Radio electronics, telecommunications technology > Semiconductor technology > Semiconductor diode > Diodes: process sub- > Hot carrier diode
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