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Published online by Cambridge University Press: 04 February 2016
Mg, the only effective p-type dopant for nitrides, iswell-studied in thin films due to the important role the impurity plays in lightemitting diodes and high power electronics. However, there are few reports of Mgin thick free-standing GaN substrates. Here we evaluate the material quality andpoint defects in GaN grown by hydride vapor phase epitaxy (HVPE) using metallicMg as the doping source. The crystal quality is typical of commercially grownHVPE substrates, and the photoluminescence measurements reveal distinctivelysharp excitonic and shallow-donor shallow-acceptor features. Secondary ion massspectroscopy indicates total Mg concentrations between 7x1016 and6x1018 cm-3 in the four separate samples studied but,more significantly, photoluminescence and electron paramagnetic resonancespectroscopy show that the Mg is incorporated as a shallow acceptor.