Magnesium incorporation in GaN grown by molecular-beam epitaxy

A pronounced dependence of Mg incorporation on surface polarity was observed in a series of Mg step-doped epitaxial GaN layers grown by rf-plasma-assisted molecular-beam epitaxy. Incorporation was studied for both (0001), or Ga-polarity and (0001̄) or N-polarity orientations. Up to a factor of 30 times more Mg was incorporated in Ga-polarity layers under certain conditions, as determined by secondary ion mass spectrometry. Measurements indicate surface accumulation of Mg occurs during growth, with stable accumulations of close to a monolayer of Mg on the Ga-polarity surface. The presence of atomic hydrogen during growth significantly increased incorporation of Mg without also incorporating potentially compensating hydrogen.