Two‐dimensional electron gas in cubic Al x Ga 1– x N/GaN heterostructures

We report on the optical and electrical properties of cubic AlxGa1–xN/GaN heterostructures. The optical properties were investigated by photoluminescence measurements. A luminescence band at 3.250 eV was observed with our cubic AlxGa1–xN/GaN heterostructures. The emission lies between the excitonic emission of c-GaN at 3.276 eV and the donor-acceptor transition at about 3.135 eV. With increasing excitation power we find a characteristic blue shift of 4.5 meV/decade. To confirm the existence of a two-dimensional electron gas the transition energy versus externally applied voltage has been investigated. A 1.3 meV/V shift was measured and quantitatively verified by a self consistent solution of the Schrodinger and Poisson equation. The electrical properties were determined by capacity-voltage (CV)-measurements. The measured carrier profile is in excellent agreement with theoretical simulations and showed a sheet carrier concentration up to n = 1.6 × 1012 cm–2 at the AlxGa1–xN/GaN interface. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)