Carbon-doped p-type (0001) plane AlGaN (Al=0.06 to 0.55) with high hole density

摘要

In this paper, promising experimental results for the p-type electrical properties of carbon-doped (C-doped) AlGaN are discussed. P-type conductivity was experimentally achieved in C-doped (0001) plane AlGaN layers with from a small amount to 55% solid Al composition, but not in (0001) plane GaN. The maximum free hole density (determined by van der Pauw geometry-Hall effect measurement) achieved for an AlGaN layer with 10% solid Al composition was p= 3.2 × 10~(18) cm~(-3). The maximum net ionized acceptor densities (NIAD = (NA~-ND_~+)), which were determined by capacitance-voltage measurement, for AlGaN with 6, 10, 27, and 55% solid Al compositions, were all in the range of (3-7) × 10~(18) cm~(-3). Moreover, the electrical activity of the carbon acceptors was estimated to be 55-71% from the NIAD and secondary-ion microprobe mass spectrometry analysis data on the carbon concentration. Activation energy of carbon acceptors was estimated to be 22-30 meV from this electrical activity. On the other hand, optical property of C-doped AlGaN was compared with undoped AlGaN. Then we found new emission, which related to carbon acceptors, at smaller energy side by 29-35 meV from band edge-emission of the AlGaN. A p-n junction was also fabricated using the C-doped p-type AlGaN.