Co-sputtering Method Mg-doped Gan Nanostructures And Research

GaN is an excellentⅢ-Ⅴwide-band gap semiconductor material,commonly used in blue or green light-emitting diodes or laser diodes,and all kinds of radioresistance, high-frequency,high-temperature and high-density integrated devices.Nanowires, nanobelts,and nanorods are a new class of one-dimensional materials that have been attracting a great deal of interest in research in the last few years.In order to improve its performances in both electronic and optoelectronic devices,however,appropriate doping is necessary.Be,Mg Zn,C have been used to study the P-doping of GaN,Mg has been widely usded.So on the base of the growth of one-dimension GaN nanostructures,It is very interesting to investigate the growth of Mg-doped GaN nanostructures.In this paper,Mg-doped GaN one-dimensional nanosmaterials were synthesized through magnetron sputtering and ammoniating progress.The structure,elemental composition,morphology and photoluminescence properties of the GaN nanomaterials were determined by X-ray diffraction(XRD),Scanning electronic microscope(SEM), High-resolution transmission electronic microscope(HRTEM),Fourier transformed infrared spectroscopy(FTIR),X-ray photoelectron energy spectroscopy(XPS) and Photoluminescence spectroscopy(PL).The growth mechanism of these GaN nanomaterials were proposed and discussed based on the investigation of the influence of the ammoniating temperature,ammoniating time and the thickness of Mg layer on the properties of Mg-doped GaN nanostructure.1.Synthesis of one-dimensional Mg-doped GaN nanostructures through co-sputtering and ammonification methodOne-dimension Mg-doped GaN nanomaterials were fabricated through ammoniating Mg:Ga₂O₃ thin films deposited by direct current(DC) magnetron sputtering system and radio frequency(RF) magnetron sputtering system respectively.The influences on the growth of GaN nanostructures were investigated by changing the ammoniating temperature,ammoniating time or the thickness of Mg layer.The results reveal that different anneal temperature,different ammoniating time of Mg:Ga₂O₃ thin films and different thickness of Mg layer have a great influence on the synthesis of GaN nanostructures.The synthesized nanostructures were of hexagonal wurtzite single-crystal GaN.There were 25 cycles in this process,the total thickness of the Mg: Ga₂O₃ thin films was about 600nm and the total sputtering time was 100 min.The single sputtering cycle was that:first an un-doped Ga₂O₃ film was deposited to a thickness of about 20 nm,and then a Mg layer was deposited for 2 s.In the second step,as-deposited Mg:Ga₂O₃ thin films were ammoniated in a conventional tube furnace at 900℃for 15 min.2.Optical properties of GaN nanostructuresThe nanowires showed four emission peaks at 359 nm,384 nm,425 nm,and 442 nm, respectively.An obviously blueshift of the band gap emission occurs from the 370 nm of bulk GaN to 359 nm of Mg-doped GaN,which is attributed to Burstein-Moss effect. The other peaks are arisen from the transtion excition of different impurity levels from Mg.3.Exploration of the growth mechanism for GaN nanostructuresIn the ammoniating process,NH₃ decomposes into NH₂,NH,H₂,N₂ and N when the ammoniating temperature is above 800℃.The Ga₂O₃ particles are reduced to gaseous Ga₂O by H₂ and then GaN molecules are synthesized through the reaction between Ga₂O and NH₃.The formed GaN molecules diffuse and agglomerate into GaN crystalline nuclei,and then the very small GaN crystalline nuclei grow up gradually with the progress of the ammonification.When the microcrystalline grow along the same direction,they become nanowires,nanorods or nanograins.In the sputtering process, layered structure of the Ga₂O₃ films doped with Mg has been obtained.Thus,in the growth process,Mg has more opportunity to substitute the position of Ga.At that temperature,vapourized Mg was doped into the GaN particles to occupy the position of Ga vacancies.