Reduction of the dislocation density in HVPE-grown GaN epi-layers by an in situ SiN x treatment

Abstract

A new method has been approached to reduce the dislocation density in hydride vapor phase epitaxy (HVPE)-grown GaN epi-layers. By this method, state of the art quality, GaN layers were grown on sapphire substrates with an in situ treatment of SiN x in HVPE process. It was found out that the in situ treatment worked most effectively when introduced after the deposition of the nucleation layer (NL). Amorphous SiN x served as a mask allowing only selective growth of GaN seeds as confirmed by scanning electron microscopy (SEM) analysis and thus a reduction of the dislocation density (down to 10 6 cm −2) with one order of magnitude lower compared to the standard samples (grown without the SiN x treatment) was obtained. Transmission electron microscopy (TEM) studies revealed that dislocations with a mixed (both screw and edge component) character mostly thread into the GaN layer. Low-temperature photoluminescence showed good optical quality of the layers grown with optimal position of SiN x treatment.