Comprehensive Study of Electron Conduction and Its Compensation for Degenerate Si‐Doped AlN‐Rich AlGaN

Abstract

The resistivity, electron concentration, mobility, and luminescence property of AlGaN epilayers with various AlN contents (x) are systematically investigated as a function of Si‐doping concentration ([Si]). In x of 59–78%, the resistivity decreases with increasing [Si] up to 4 × 1019 cm−3. The temperature dependence of the electron concentration and mobility disappears in the optimum doping range, characteristic of electric degeneracy. The ionization energy of isolated Si donor (Ed0) is slightly increased in the range of 60–80 meV with increasing x (59–78%). At higher [Si] than 4 × 1019 cm−3, self‐compensation defects such as III vacancy–Si complexes are formed, resulting in higher resistivity. When x is 89%, the resistivity is approximately one order of magnitude higher than that for lower x, and the Ed0 is drastically increased to ≈120 meV, which is a feature of a highly compensated semiconductor. Based on the increased oxygen incorporation and the distinctive defect luminescence peak for the sample with x of 89%, the formation of acceptor‐type O‐related defects such as O‐DX and VIII‐nON is indicated and can contribute to a part of the electron compensation.