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The Theoretical Research And Preperation Of BN Coated With GaN Nanowires Composite Structure

Posted on:2017-10-25Degree:MasterType:Thesis
Country:ChinaCandidate:H K ZhaoFull Text:PDF
GTID:2518306512454414Subject:Physical Electronics
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Gallium nitride(GaN)is an important third generation wide band gap semiconductor materials in group III-V,which has stable physical and chemical properties,excellent photoelectric properties,so it can be used for ultraviolet detectors,high temperature and radiation detectors,high frequency and high power microwave devices,etc.As an important way to improve the application of GaN in optoelectronic devices,coating is widely concerned and used by scientists.Boron nitride(BN)is a direct band gap semiconductor material,which has the same structure and similar lattice constants with GaN,it is widely used in field emission devices and light-emitting diodes due to its excellent physical properties and low electron affinity.Thus,to synthesis BN coating GaN nanowires composite structure is expected to improve the performance of field emission and the light emitting device.This paper analyzes the properties of BN coating GaN nanowires composite structure and the preparation of CVD by theory and experiment two parts.Theoretically,the electronic structures and work functions of BN coating GaN nanowires composite structure have been investigated by a first principle density functional theory(DFT).The results show that the band gaps of BN coating GaN nanowires composite structures are slightly widened,the bottom of the conduction band shift high energy and the electron affinity are slightly reduced;The electronic structure of GaN nanowires modified by BN coating GaN nanowires,the localized charges on the bottom of the conduction band of BN coating GaN nanowires composite structures are mainly distributed around the B atom,N atom and the Ga atom which near the B atom,The work function(WF)of GaN nanowires is slightly reduced by BN coated.Experimently,the synthesis of BN coating GaN nanowires composite structures using chemical vapor deposition(CVD)method,first of all we prepared GaN nanowires that has relatively good shape on the Si substrate,then we use a different precursors to synthesize BN that will be coated on the GaN nanowires.X-ray diffraction(XRD),scanning electron microscopy(SEM)and energy dispersive spectrometer(EDS)are used for characterizing the samples which synthesized by different precursors,objective to find out the B source of BN coated GaN nanowires with better morphology,meanwhile,we study the effect of temperature on the best precursor.The results show that:The coating of B2O3and C powder is better;the best temperature is 800?,the reaction temperature is important,which is too low make nanowires to not completely and too high lead to lamellae;The growth mechanism of GaN nanowires is V-L-S,the growth mechanism of BN coating is V-S.
Keywords/Search Tags:BN coating GaN nanowires composite structure, Density Functional Theory, Work Function, Chemical Vapor Deposition, Secondary growth
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