Growth and photoluminescence studies of Zn-doped AlN epilayers

Deep ultraviolet time-resolved photoluminescence (PL) spectroscopy has been employed to study Zn-doped AlN epilayers grown by metal-organic chemical vapor deposition. The PL spectra of Zn-doped AlN epilayer exhibited two impurity emission lines at 5.40 and 4.50 eV, which were absent in undoped epilayers and assigned to the transitions of free electrons and electrons bound to nitrogen vacancies with three positive charges (0.90 eV deep) to the Zn-0 acceptors. By comparing PL spectra of Zn- and Mg-doped AlN epilayers with undoped epilayers, it was deduced that Zn energy level is about 0.74 eV, which is about 0.23 eV deeper than the Mg energy level (0.51 eV) in AlN. It is thus concluded that contrary to theoretical prediction, Zn would not be a better candidate than Mg as an acceptor dopant in AlN.