Acceptor-bound exciton transition in Mg-doped AlN epilayer

Mg-doped AlN epilayers grown by metalorganic chemical-vapor deposition have been studied by deep ultraviolet time-resolved photoluminescence (PL) spectroscopy. A PL emission line at 6.02 eV has been observed at 10 K in Mg-doped AlN, which is about 40 meV below the free-exciton transition in undoped AlN epilayer. Temperature dependence of the PL intensity of this emission line also reveals a binding energy of 40 meV. This transition line is believed to be due to the recombination of an exciton bound to neutral Mg acceptor (I-1) with a binding energy of E-bx=40 meV. This value is also about 10% of the energy level of Mg impurity in AlN satisfying Haynes' rule. The recombination lifetime of the I-1 transition in Mg-doped AlN has been measured to be 130 ps, which is close to the expected value. The larger E-bx of the acceptor-bound exciton in AlN than that in GaN is due to large effective masses of the electrons and holes, as well as the energy level of Mg impurity. (C) 2004 American Institute of Physics.