High performance of Ga-doped ZnO transparent conductive layers using MOCVD for GaN LED applications.

High performance of Ga-doped ZnO (GZO) prepared using metalorganic chemical vapor deposition (MOCVD) was employed in GaN blue light-emitting diodes (LEDs) as transparent conductive layers (TCL). By the post-annealing process, the annealed 800°C GZO films exhibited a high transparency above 97% at wavelength of 450 nm. The contact resistance of GZO decreased with the annealing temperature increasing. It was attributed to the improvement of the GZO crystal quality, leading to an increase in electron concentration. It was also found that some Zn atom caused from the decomposition process diffused into the p-GaN surface of LED, which generated a stronger tunneling effect at the GZO/p-GaN interface and promoted the formation of ohmic contact. Moreover, contrast to the ITO-LED, a high light extraction efficiency of 77% was achieved in the 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 promising for the development of GZO using the MOCVD technique for GaN LED applications.