Dislocation reduction in HVPE GaN via high temperature pretreatment of MOCVD-GaN/sapphire substrate

In this paper, decomposition pits on the MOCVD-GaN/sapphire substrate were fabricated by the high temperature pretreatment (HTP) process for the purpose of reducing dislocations in the subsequently grown GaN by hydride vapor phase epitaxy (HVPE). The impact of atmosphere, temperature, and time during HTP on the substrate morphologies was characterized by scanning electron microscopy and transmission electron microscopy. The optimum HTP process was confirmed and integrated with the GaN growing process by HVPE. Cathodoluminescence and molten KOH–NaOH eutectic etching were used to evaluate the dislocation density of HVPE GaN. The dislocation density was reduced by orders of magnitude to 105 cm−2. The results indicated that the high temperature pretreatment process can effectively reduce dislocations of HVPE GaN.