Defect Reduction in GaN films using in-situ SiNx Nanomask

The usefulness of non-polar and semi-polar group-III nitrides such as gallium nitride (GaN) and its alloys has been well established for its use in the fabrication of optoelectronic and high-powered electronic devices. Given recent trends in industry standards there is considerable interest in the growth of nonpolar (a- and m-plane) GaN based epitaxial films. The problems associated with the growth of these nonpolar GaN based films is characterized by high defect density, reduced carrier mobility, and low reliability which all contribute to an overall lower efficiency. However, high performance devices can be achieved by eliminating these defects by improving the structural quality of the nonpolar GaN films.

Researchers at the University of California, Santa Barbara have developed an efficient method to significantly reduce defects in non-polar and semi-polar group-III nitride films. Through the use of in-situ SiNx as a nanomask when growing GaN substrates, researchers have demonstrated reduced stacking fault density, reduced thread dislocation density, reduced surface roughness, reduced sub-micron pits, and increased luminescence. Compared to the lateral epitaxial overgrowth (LEO) technique, this invention has the advantage of being a simple process that avoids contamination characteristic of the ex-situ process used in LEO. Unlike LEO, this new process also facilitates nanometer scale lateral epitaxial overgrowth at the open pores of the film which reduces the differences between the wing and window regions of film which has adverse effects on devices if untreated. All structure improvements contribute to an overall reduction of defects uniformly across the film which significantly increases the efficiency of the material.