The Preparation Of Phosphorus-doped GaN Nanowires And Study Of First-principle

Gallium nitride(GaN)is an important semiconductor material that has a direct wide band gap of 3.4 eV.Moreover,due to high thermal conductivity,low work function(4.1 eV),and low electron affinity(2.7-3.3 eV),it may be a promising material for field emission displays,and vacuum nano-electronic devices.In this thesis,phosphorus-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 effect of the ammoniation temperature,ammoniation time,and the rate of NH3 gas on the morphology of phosphorus-doped GaN nanowires.Then studied the morphology,composition and structure of phosphorus-doped GaN nanowires parepared under the different doping mass ratio,and selected a good quality sample to test its field emission properties.At last,we studied the electronic properties of phosphorus-doped unsaturated and saturated GaN nanowires using first-principle density functional theory(DFT).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,according to analyze the effect of the ammoniation temperature,ammoniation time,and the rate of NH3 gas on the morphology of phosphorus-doped GaN nanowires,we had obtained the results that(1)Ammonization temperature and ammonia time influence lengths and diameters of phosphorus-doped GaN nanowires;(2)Ammonia flow may change the density of the phosphorus-doped GaN nanowires on the Si subtract.Secondly,when the phosphorus with small proportion in nanowires,it has few effect on the morphology of nanowires.But with increasing the doping ratio,it is possible to induce the rough surface and changing the crystalline for nanowire.Thirdly,Field-emission measurements showed that the field emission properties of phosphorus-doped GaN nanowires depend on the aspect ratio and morphology of GaN nanowires.The samples present good field emission properties.Fourth,the electronic properties of phosphorus-doped GaN nanowires were calculated from density functional theory(DFT),the introduction of phosphorus 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.