Theory of the composition dependence of the band offset and sheet carrier density in the GaN/AlxGa1-xN heterostructure
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We present a systematic study of the sheet carrier density and valence-band offset in the GaN/AlxGa1-xN(0001) heterostructure as a function of x from ab initio density-functional methods. We find that the calculated sheet carrier density increases rapidly with x for xless than or equal to0.3 in good agreement with experiments, but beyond this concentration, it quickly saturates to a value of about 2x10(13) cm(-2). The band offset shows a small asymmetry between the Ga-face and N-face interfaces and changes more or less linearly with x, although a small bowing is found. The layer-projected densities of states indicate the formation of the two-dimensional electron gas at the Ga-face interface and confirm the absence of interface states in the gap. (C) 2004 American Institute of Physics.