The Preparation Of Se-Te Co-doped GaN Nanowires And Study Of First-principle

Gallium nitride(GaN)is a kind of excellent wide bandgap semiconductor materials.GaN has excellent photoelectric properties,thermal stability and mechanical properties,so it has attracted a lot of attention from the science and technology workers.As is well known,the electron affinity of GaN is as low as 2.7-3.3 eV.In addition,GaN also possesses high melting point,high thermal conductivity and high carrier mobility,so it is suitable for application in vacuum microelectronic devices as a field emission cathode material.Some researchers have taken many methods to improve the field emission properties of GaN nanomaterials,such as changing the morphology of GaN nanomaterials,and doping or coating GaN nanomaterials.In this thesis,Se-Te Co-doped GaN nanowires grown on Pt-coated Si(111)substrates have been synthesized by using chemical vapor deposition(CVD).First of all,we studied the electronic properties of Se-Te Co-doped saturated GaN nanowires using first-principle density functional theory(DFT).Then studied the effect of the ammoniation temperature,ammoniation time,and the rate of NH3 gas on the morphology of Se-Te Co-doped GaN nanowires.At last,we studied the morphology,composition and structure of Se-Te Co-doped nanowires parepared under the different doping mass ratio,and selected a good quality sample to test its field emission properties.This analysis addresses formation energy,crystal parameters,electronic energy band structure,density of states and charge density difference.The basic contents and results are as follows:Firstly,the electronic properties of Se-Te Co-doped GaN nanowires were calculated from density functional theory(DFT),the introduction of Se,Te can change the micro-electronic structure of GaN nanowires and reduce the work function.These can theoretically verify that the phosphorus impurities can enhance field emission properties.Secondly,according to analyze the effect of the ammoniation temperature,ammoniation time,and the rate of NH3 gas on the morphology of Se-Te Co-doped GaN nanowires,we had obtained the results that:(1)Ammonization temperature influence lengths and diameters of Se-Te Co-doped GaN nanowires;(2)Ammonia flow may change the diameters of the Se-Te Co-doped GaN nanowires on the Si subtract;(3)ammonia time influence lengths and density of Se-Te Co-doped GaN nanowires.Field-emission measurements showed that the field emission properties of Se-Te Co-doped GaN nanowires depend on the aspect ratio and morphology of GaN nanowires.At last,Field-emission measurements showed that the field emission properties of Se-Te Co-doped GaN nanowires depend on the aspect ratio and morphology of GaN nanowires.The samples present good field emission properties.