The Preparation Of GaN Nanowires And Investigation Of Its Photodetectors

GaN is a direct wide band gap?Eg=3.4eV?semiconductor with high electron mobility,high temperature resistance,anti radiation and other advantages.On the one hand,nano materials have excellent physical and chemical properties corresponding to the macroscopic materials;on the other hand,because of the crystal periodic conditions of nano materials are destroyed and show a series of properties that are superior to the corresponding macroscopic material.Based on these properties,we can make the devices with better performance easier.In order to improve the quality of GaN nanowires,the key factors of GaN nanowire growth law remains to be further studied;at the same time,semiconductor device based on GaN nanowires is still in the research stage.In this dissertation,we mainly studied the fabrication of GaN nanowires and the devices based on GaN nanowires,finally the weak signal detection amplifying circuit of UV is designed,the main conclusions are as follows:Firstly,GaN nanowires were prepared by chemical vapor deposition method using Ni as catalyst.The growth mechanism of nanowires with different morphologies under different growth conditions was investigated by controlling various critical growth conditions.Through the research on the growth temperature,The results show that with the increase of temperature,the growth of nano materials changes from axial to lateral,growth mechanism was domained by liquid solid?VLS?at first,and gradually developed to the vapor solid?VS?growth mechanism.Through the research on the growth time.The results show that with the increase of growth time,the axial growth of nano materials leading by the growth mechanism of VLS oriented gradually developed to the lateral growth leading by VS growth mechanism.Its axial growth gradually slowed down,lateral growth gradually accelerated.Through the study of reaction gas flow.The results show that when the NH₃ flow is small,The amount of evaporation of Ga is larger than that of NH₃,and the ratio of Ga/N is unbalanced,which leads to the low yield of GaN nanowires.When the NH₃ flow rate increases,you can see that GaN nanowire becomes shorter and thicker.Secondly,Full nano metal semiconductor metal?MSM?photodetectors were fabricated using GaN nanowires as active sites and Ag nanowires as transparent electrodes.The light/dark current ratio reaches 78 times under the air condition and 3V bias voltage.The rise time and the fall time constant of the detector in the air are 2.8s and 0.2s respectively.Thirdly,The influence of annealing of GaN nanowire on the device performance was investigated and the mechanism was explained.Under the bias of 3V vacuum environment,the raise time of the detector after annealing is reduced by 39.9%compared to that of before annealing.At the same time,the dark current of the detector at 1V bias is reduced to 2.6 ×10-7A after annealing by 6.1 X 10-7A before annealing.Fourthly,Do some research on the related work of UV detection and give a preamplifier circuit and simulate it.