Reduction of threading dislocations in GaN layers using in situ deposited silicon nitride masks on AlN and GaN nucleation layers

Abstract

We have examined the influence of thin layers of silicon nitride, deposited in situ on AlN and GaN nucleation layers (NLs), on the density of threading dislocations (TDs) in GaN overgrowths. Results indicate that TD density is reduced to 2–4×108 cm−2. In GaN/silicon nitride/AlN–NL/sapphire composites, alternating regions of low and high TD density coexist in the overgrowth, and microstructural features characteristic of epitaxial lateral overgrowth techniques are seen. On the other hand, such features are absent in GaN/silicon nitride/GaN–NL/sapphire composites, and TDs are uniformly distributed.