High performance of Ga-doped ZnO transparentconductive layers using MOCVD for GaN LEDapplications

Abstract

High performance of Ga-doped ZnO (GZO) prepared usingmetalorganic chemical vapor deposition (MOCVD) was employed in GaNblue light-emitting diodes (LEDs) as transparent conductive layers (TCL).By the post-annealing process, the annealed 800°C GZO films exhibited ahigh transparency above 97% at wavelength of 450 nm. The contactresistance of GZO decreased with the annealing temperature increasing. Itwas attributed to the improvement of the GZO crystal quality, leading to anincrease in electron concentration. It was also found that some Zn atomcaused from the decomposition process diffused into the p-GaN surface ofLED, which generated a stronger tunneling effect at the GZO/p-GaNinterface and promoted the formation of ohmic contact. Moreover, contrastto the ITO-LED, a high light extraction efficiency of 77% was achieved inthe GZO-LED at injection current of 20 mA. At 350 mA injection current,the output power of 256.51 mW of GZO-LEDs, corresponding to a 21.5%enhancement as compared to ITO-LEDs was obtained; results are promisingfor the development of GZO using the MOCVD technique for GaN LEDapplications