Preparation Of AZO Tnin Film And Its Application To GaN-Based Bule LED As Current Spread Layer

In this paper, Al doped ZnO films were grown by DC magnetron sputtering using a ZnO target (99.99%) containing Al₂O₃ of 2%(wt%), the performance of AZO thin films had been improved by annealing process. The ohmic characteristics of AZO/P-GaN and AZO/ITO/P-GaN were investigated. The result showed that AZO/ITO/AZO scheme could achieve ohmic contact. Using ITO/AZO composite transparent contact layer (TCL) as current spread layer, GaN-LEDs were fabricated with the size of 217um×368um.AZO thin films were deposited on quartz glass. Structural, optical and electrical properties of the films were characterized and analyzed by XRD, SPM, four point resistivity test system and visible light spectrophotometer. Optimum condition was got based on the investigation. 400nm AZO thin films were prepared, the transmittance were higher than 90%, and resistance were about 2.0×10^-3·cm.The influence of different annealing atmosphere and temperature were studied fellowed. Under N2 and H2 mixed ambience, the best annealing temperature was 600℃, after annealing 1 min, the resistance drop to 4×10^-4·cm.The ohmic characteristics of AZO/P-GaN were investigated, the experiment showed that it was hard to get ohmic contact between AZO and P-GaN. Based on the fact that ITO (deposit by e-beam evaporator) contacts to P-GaN exhibit ohmic characteristic, we inserted ITO as intermediate, and finally achieved ohmic contact.With the size of 217μm×368μm,GaN-LEDs used ITO /AZO composite TCL as current spread layer exhibited dominant wavelength of 456.6nm, work voltage of 3.8V and output power of 21.5mW at 20mA.