Study On Ga-doped ZnO Film Prepared By Double-target Reactive Magnetron Sputtering And Its LED Application

Nowadays，indium tin oxide (ITO) is one of the most widely used materials inindustry for transparent conducting oxide (TCO). However the ITO raw materials arenot environmentally friendly. Besides, the ITO materials are especially scarce in naturesource. Doped ZnO films have potential advantages, such as excellent optical andelectrical properties, wide band gap (3.30eV), non-toxic and low price. Due to goodoxidation resistance, similar lattice deformation to ZnO materials, and high dopingefficiency, Ga doped ZnO (GZO) is considered to be one of the most potential materialsto replace ITO as transparent conductive films. It is very necessary to reduce the cost ofGZO films, improve its overall performance and broaden its application field.In this study, transparent conduction Ga-doped ZnO films were prepared bydouble-target reactive magnetron sputtering using Zn target and ceramic Ga2O3target.Then the GZO films were annealed to improve its overall optical and electricalperformance. After annealing, GZO films were set as the current diffusion layer of LEDdevices. The following issues were studied in detail such as the effects of processparameters of double-target reactive magnetron sputtering on the structure of GZO film,the influences of doping and annealing on the structure, optical and electricalcharacteristic, the effect of thickness of GZO film on the I-V characteristic curves andintensity of electroluminescence of LED devices.The above-mentioned sputtering experiments indicate that the crystallinity is moreprefer oriented strengthened and the grain size is increased with the increasing ofsubstrate temperature. An optimum value of GZO film crystalline quality can beobtained by increasing the sputtering pressure and the ratio of oxygen and argon gasflow. When the sputtering power of Ga2O3ceramic target is130W, Zn target sputteringpower has great impact on the doping of GZO films. The optimum depositionparameters is as following substrate temperature of500℃, sputtering pressure of1.0Pa,150W sputtering power with Zn target,130W sputtering power with Ga2O3ceramictarget. It can be prepared under the optimum deposition parameter for the high qualityGZO films, the lowest resistivity of2.43×10-4Ω·cm and the average transmittance invisible region of80%. Furthermore, the annealing treatments fellowed significantlyimprove the crystal structure in the mixed gases of95%nitrogen and5%hydrogen. The GZO transparent conductive films with different thickness were also depositedon the GaN exitaxial wafers and sapphire substrate. With the increase of film thickness,the Hall mobility is increased while the resistance is significantly decreased, the visiblelight transmittance being to be decreased. The minimum resistance is1.96×10-4Ω·cmwhen the thickness of GZO films is650nm. The average transmittance in the visiblespectrum region was more than80%.The Ohmic contact can be obtained when setting170~720nm GZO transparentconductive film as a current spreading layer on the GaN-based LED epitaxial wafers.The corresponding LED chips can be lighted on. The electroluminescence experimentresults indicate there has the largest light outpot power of LEDs when the thicknesses ofGZO films are170nm.