The Field Emission Properties Of P-doped GaN Nanowires In Different Concentrations

The representative of ?-? compound semiconductor materials,GaN,is becoming a kind of promising material for field emission displays and vacuum nano-electronic devices because it has a wide direct band gap(3.39 eV),low wave function,stable physical and chemical properties,high mechanical strength and small electron affinity(2.7-3.3 eV).The field emission display devices which made of GaN material have a longer lifetime compared with the devices made of Si or other traditional materials.The main research in this thesis is the emission properties of phosphorus doped GaN nanowires in different concentrations.For the theoretical research,we built molecular models for P-doped GaN nanowires and calculated the combine energy and wave functions based on the first-principle density functional theory to analysis the electronic properties and wave functions for the emission properties of P-doped GaN nanowires.First,the outcome of combine energy shows that it is easy for single P atom to replace Ga atoms on the outermost surface position to get the stable structure in molecular model.As for double and triple P-doped GaN nanowires,the tendency of P atoms is likely to take place the outermost surface Ga atoms to form symmetry highly structures.Then the doping P atoms changed the band structure and reduced the band gap of GaN nanowires.The wave function reduced obviously by increasing the number of doping P atoms.Compared with the intrinsic GaN nanowires,the lowest wave function of P-doped GaN nanowires is 3.097 eV,which is the single P atoms doped.Combined with the theoretical research,the experimental work is the synthesis of P-doped GaN nanowires via Chemical Vapor Deposition by controlling the reaction conditions in different concentritions,which is 2.24%,3.52%and 6.43%.They are similar to theoretical calculation concentritions 2.08%,4.17%and 6.25%.Ga2O3 and NH3 as the raw materials,P2O5 as the doped source.The prepared samples were characterized by SEM,EDS,XRD and TEM,the obtained P-doped GaN nanowires has hexagonal wurtzite structure,and P atoms had doped into GaN nanowires.The results of emission text show that turn-on field of the sample in 2.24%is 2.85 eV/?m,which is the minimum in three different concentrations.The doping P atoms in GaN nanowires has improved the emission properties,and low doped concentration has a great influence compared with other concentrations.