High Quality p-Type GaN Deposition on c-Sapphire Substrates in a Multiwafer Rotating-Disk Reactor.

Very high quality p-type GaN thin films have been epitaxially grown on c-sapphire substrates by the MOCVD technique in a multiwafer rotating-disk reactor at 1040°C with a GaN buffer layer of ∼200 A grown at 530°C. The undoped GaN films have a low n-type background carrier concentration of ∼5 x 10 16 cm -3 with an x-ray FWHM GaN(0002) of 280 arc-sec across the 1 in. substrate. Biscyclopentadienyl magnesium (Cp 2 Mg) was used as the precursor Cp 2 Mg, the p-dopant. The Mg-doped GaN wafers retained an excellent surface morphology. In addition, after post annealing in N 2 ambient at ∼700°C for an hour, the Hall measurements show 6.7 x 10 17 to 5.2 x 10 18 cm -3 carrier concentration depending on Cp 2 Mg flow rate, with a hole mobility of 10-20 cm 2 /V-s which is the best mobility for those hole concentrations reported in the literature to date.