Synthesis And The First Principles Study Of Sn Doped GaN Nanowires

GaN is a ?-?compound semiconductor materials with a wide direct band gap?3.4 eV?,which has stable physical and chemical properties,high thermal conductivity,large saturated electron drift velocity,high critical breakdown electric,small electron affinity?2.7-3.3 eV?and work function?4.1 eV?,it is widely used in the new devices,new technology applications,such as short-wavelength light emitting devices,microwave,high frequency and high-power semiconductor devices,etc.One-dimensional GaN nanowires belong to nano-scale,have a large aspect ratio and nano-emitter tip.With respect to bulk GaN,it presents many special nano-effects.Hence,one-dimensional GaN nanowires were regarded as an ideal candidate material for field emission cathodes,become a hot research around the world.Experimental preparation and theoretical calculation of the Sn-doped GaN nanowires were mainly studied in this work.In the experimental part,one-dimensional Sn-doped GaN nanowires were synthesized by chemical vapor deposition method in Pt-catalyzed Si?111?substrate,and Ga₂O₃ and NH₃ as the raw materials,SnO₂ as the doped source.The prepared samples were characterized by SEM,XRD,EDX,and tested by field emission measurement,the results showed that:?1?ammoniation temperature mainly have an effect on morphology of the samples,ammonia flow mainly affect the diameter of nanowires,ammoniated time is the main effects for the length of nanowires,the good morphology of Sn-doped GaN nanowires sample was synthesized under1050?,200sccm,20min conditions;?2?the prepared Sn-doped GaN nanowires are hexagonal wurtzite structure,and Sn atoms were doped into the GaN nanowires;?3?field emission tests showed that Sn-doped GaN nanowires have better field emission property,turn-on field of the sample with 1:20?quality ratio?is 8.7 V/?m,and turn-on field of the sample with 1:10?quality ratio?is only 4.4 V/?m,which are sufficient for applications of field emission displays and vacuum micro-electronic devices.In the theoretical part,electronic structure and work function of the Sn-doped H-passivated GaN nanowires were studied using the first principles based on density functional theory.By comparing electronic structure and work function of different concentrations of the Sn doped H-passivated GaN nanowires,we got the following conclusions:?1?Sn atom is pleased to substitute Ga atoms on the outermost surface of GaN nanowires,and the most stable structures of double atoms,three atoms Sn doped system were determined;?2?the volume of GaN nanowires would increased with introducing Sn dopant,the symmetry of the original structure would been destroyed;?3?Sn dopant have little effect on band gap of the H passivated GaN nanowires,but introduce the impurity levels in the band gap,which attributed to the strong interactions between Sn and adjacent N atom;?4?the workfunction of double and three Sn atoms doped GaN nanowires systems are less than undoped system,it predicted Sn dopant can improve the field emission properties of GaN nanowires in theoretically.