Improved GaN Substrates Prepared with Ammonothermal Growth

The usefulness of gallium nitride (GaN) and its alloys has been well established for its use in the fabrication of optoelectronic and high-powered electronic devices. Most commercially available GaN-based devices are grown on conventional c-plane surfaces. The use of c-plane surfaces has disadvantages, which limit the performance of resulting devices. Recent studies have pointed out several benefits and advantages of growing m-plane devices. Despite these benefits, current technology is limited due to poor smoothness of m-plane surfaces.

Researchers at the University of California, Santa Barbara have developed a method for growing m-plane GaN using an ammonothermal growth technique. Using this method, m-plane growth results in smoother surfaces than c-plane growth. M-plane growth has associated benefits such as p-type doping and inverted polarization charge. High p-type conductivity improves device efficiency, while transistors grown on m-plane GaN overcome high gate leakage problems of traditional GaN transistors. M-plane optical devices also experience higher emission efficiency due to the absence of a polarization field, and their optically active layer usually has higher Indium incorporation, allowing for longer wavelength emission. This novel method also reduces processing steps because flip-chip bonding and de-bonding steps are no longer needed to expose the m-plane of the growth.