Combined hydride and metal organic vapor-phase epitaxy of GaN on sapphire

We describe a method to produce GaN epitaxial layers in a single chamber where a low-temperature buffer layer is deposited using metalorganic vapor-phase epitaxy (MOVPE), followed by conventional hydride vapor-phase epitaxy (HVPE) of GaN at higher temperatures. While a typical 12μm sample is investigated here, the GaN film thickness can vary between 2 and 200μm, with HVPE growth rate ranging from 5 to 60μm∕h. Cross-sectional transmission-electron microscope images show a dense network of mixed dislocations, whose density is significantly reduced after 6μm to the high 107cm−2 range. 10 K photoluminescence shows bound exciton dominated emission associated with the A and B valence bands and phonon replicas. No yellow emission is observed. This versatile process can be extended to produce additional device layers by MOVPE.