Photoluminescence studies of impurity transitions in AlGaN alloys

Abstract

Deep ultraviolet photoluminescence (PL) spectroscopy has been employed to investigate impurity transitions in Si doped Al-rich AlGaN alloys. In addition to the previously reported donor compensating centers—isolated cation vacancy with three negative charges (VIII)3− and cation vacancy complex with two-negative charges (VIIIcomplex)2−—a group of impurity transitions with higher emission energies has been observed in AlGaN alloys grown under different conditions, which has been assigned to the recombination between shallow donors and cation vacancy complexes with one-negative charge (VIIIcomplex)−1. Similar to (VIII)3− and (VIIIcomplex)2−, the energy levels of (VIIIcomplex)1− deep acceptors in AlxGa1−xN (0⩽x⩽1) alloys are pinned to a common energy level in vacuum. A strong correlation between the resistivity and PL emission intensities of the impurity transitions associated with cation vacancies (and complexes) was found.