P-type conductivity in bulk AlxGa1-xN and AlxGa1-xN/AlyGa1-yN superlattices with average Al mole fraction > 20%

Abstract

Synchrotron radiation photoemission spectroscopy reveals enhanced oxygen incorporation in AlxGa1-xN as the Al mole fraction increases. It is shown that the increased oxygen donor incorporation can result in a conductivity-type change from p-type to n-type in Mg-doped AlxGa1-xN. Consistent with the conductivity-type change, epitaxial Al0.20Ga0.80N films exhibit n-type conductivity despite heavy Mg doping. The p-type conductivity of bulk AlxGa1-xN with a high Al mole fraction can be improved by employing AlxGa1-xN/AlyGa1-yN superlattices (SLs). At 300 K, Mg-doped Al0.17Ga0.83N/Al0.36Ga0.64N SLs (average Al mole fraction of 23%) exhibit strong p-type conductivity with a specific resistance of 4.6 Omega cm, a hole mobility of 18.8 cm(2)/Vs, and an acceptor activation energy of 195 meV. (C) 2004 American Institute of Physics.