Wide band-gap semiconductors, such as zinc oxide (ZnO) and gallium nitride (GaN) are getting a lot of attention for their applications in optoelectronic and power devices. Single crystal GaN, a III-V wide band-gap semiconductor, has received a great deal of attention in the recent past due to its potential for the realization of photonic devices such as laser and light emitting diodes (LEDs) operating in the ultraviolet portion of the electromagnetic spectrum as well as solar-blind photo-detectors.