This article was presented as part of Symposium G, "Gallium Nitride and Related Alloys" at the 1998 Fall Meeting of the Materials Research Society held in Boston, Massachusetts, November 30-December 4.

Abstract

Nitride-based device structures for electronic and optoelectronic applications usually incor-porate layers of Al_xGa_1-xN, and n- and p-type doping of these alloys is typically required. Ex-perimental results indicate that doping efficiencies in Al_xGa_1-xN are lower than in GaN. We ad-dress the cause of these doping difficulties, based on results from first-principles density-functional- pseudopotential calculations. For n-type doping we will discuss doping with oxygen, the most common unintentional donor, and with silicon. For oxygen, a DX transition occurs which converts the shallow donor into a negatively charged deep level. We present experimental evidence that oxygen is a DX center in Al_xGa_1-xN for x>~0.3. For p-type doping, we find that compensation by nitrogen vacancies becomes increasingly important as the Al content is in-creased. We also find that the ionization energy of the Mg acceptor increases with alloy compo-sition x. To address the limitations on p-type doping we have performed a comprehensive inves-tigation of alternative acceptor impurities; none of the candidates exhibits characteristics that surpass those of Mg in all respects.

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Cite this article as: MRS Internet J. Nitride Semicond. Res. 4S1, G10.4 (1999).

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