Berlin 2005 – scientific programme
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HL: Halbleiterphysik
HL 51: GaN: Pr
äparation und Charakterisierung III
HL 51.8: Talk
Tuesday, March 8, 2005, 12:30–12:45, TU P-N202
Electrical and Optical Properties of Highly Si-Doped AlN — •Martin Hermann1, Florian Furtmayr1, Markus Maier1, Martin Stutzmann1, Eva Monroy2 und Martin Eickhoff1 — 1Walter Schottky Institut, Technical University Munich, Am Coulombwall 3, D-85748 Garching, Germany — 2CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France
Within the group III-nitride alloy system, AlN has the widest direct band gap of 6.2 eV, which makes it a useful material for optoelectronic applications in the UV spectral regime. For such applications the achievement of controllable n-type conductivity is crucial. Silicon, known as shallow donor in Ga-rich AlGaN alloys, is considered as the preferable donor in AlN. Due to its high ionization energy, it is difficult to achieve a significant conductivity. One possible approach is the increase of the Si-concentration above the threshold for impurity band formation, estimated to approximately 1 at. %.
We present a systematic study of highly Si-doped AlN layers grown by MBE on c-plane sapphire. Electrical characterization revealed an increasing donor ionization energy up to 240 meV for a Si content of 1.1× 1021 cm−3. For higher silicon concentrations we observed a sharp increase in conductivity by four orders of magnitude, attributed to the onset of impurity band conduction.
In addition, optical characterisation by absorption and cathodoluminescence measurements were performed and the influence of strong Si-doping on the optical properties of AlN is discussed.