The Photoelectric Transport Properties Induced By B~+Doping Of Nanotube Mosfet

When the device scale in the nanometer range, great deal of new phenomena are being shown up with its potential value in application. At the same time, the hollow tubular structure of nanometer tube has its incomparable advantages in the molecular storage and transport, bound by chemical reaction, light and gas sensor; The unique structure and quantum limit field effect makes the nanotubes show unusual electrical, optical, mechanical and magnetism phenomenon. Nanotubes MOSFET performance has many advantage, it have already attracted the lots of attention among the people.In this paper, firstly, I took the advantages of the two dimensional numerical simulation of the field-dependence mobility model to research the boron doped nanotubes MOSFET transport properties. Such as the effect on transport properties by doping concentration of conductive part, the thickness of SiO2layer, the resistance and measurement of the conductive part (Si shell) and the photocurrent generated by extra light source.The research result demonstrate that the higher the doping concentration is, the better conductivity is. The reason is that doping increased carrier concentration and then increased μ. Additionally, the thicker the Si shell is and the shorter lengths the nanotube has, the smaller resistance the conductive part is and result in the better conductivity, but the thickness of Si shell shoule not be too thick and the length of the conductive part should not be too short, otherwise such negative effects as current collapse, the declining of device’s breakdown characteristic, the increasing or decreasing of sensitivity for the control of gate voltage and so on will be emerged. With regard to the thickness of SiO2, the situation a little bit more complex. As a p-channel FET. When Vg>0, the thicker the SiO2is, the better conductivity is. When Vg<0, the thinner the SiO2is, the better conductivity is. As a n-channel FET, the situation is opposite. All of above are decided by the potential barrier height and the location of EF,Our theoretical results qualitative agreement with the experimental results, and further optimize the device model in order to achieve more excellent transport properties.Secondly, I studied research on the device external environment parameters (plus light) of silicon shell nanotubes MOSFET transport properties in great detail. The results show that when the incident light wavelength is equal to semiconductor intrinsic absorption limit, the light response of semiconductor achieve maximum which means the current be produced achieve maximum value, and when the incident light wavelength is longer than the limitation of semiconductor intrinsic absorption limit, the light response will drop rapidly. Additionally, photocurrent increases when increasing the shell thickness of Si, and it’s reaches the maximum when the shell thickness of Si thick up to60nm. When further increasing the shell thickness, photocurrent begins to decrease. This phenomena can be understood as follows:when the wavelength of incident light is close to absorbed layer (the Si shell) thickness, absorption dominates, increasing shell thickness would reduce absorption and enlarge diffusion, and this tow effect tend to an equilibrium state, thus photocurrent increases. However, when the wavelength of incident light is much smaller than shell thickness, diffusion dominates and increasing shell thickness would further make diffuison more dominant and absorption weaker, thus photocurrent diminishes.When the diffusion and absorption effect of absorption layer in equilibrium, the photocurrent achieve maximize. And the photocurrent along with the increase of the intensity of light and monotone increasing.Last but not least, I detailed research on the density distribution of majority carrier-hole. It is concluded that the difference work function between two materials caused the hole depletion.The obtained results have shown that we can combine the factors which affect the transport properties of core/shell nanotube MOSFET to enhance the conductivity by debugging and controlling in the whole and to achieve the goal of efficient transport in nanotube MOSFET.