Time-resolved spectroscopy of strained GaN/AlN/6H-SiC heterostructures grown by metalorganic chemical vapor deposition

Temperature-dependent time-resolved photoluminescence measurements were per formed on GaN film/AlN buffer/6H-SiC substrate heterostructures grown by me talorganic chemical vapor deposition. The overlying GaN layers were under t ension, as estimated from the free A exciton (FEA) position. The recombinat ion lifetimes were determined for the FEA and for the neutral-donor-bound e xciton (D0X). We observed that the recombination lifetime for the FEA has t he same value of 40-50 ps in all the layers, whereas the recombination time for the D0X varies for different samples. We observed that the recombinati on lifetimes for D0X have a clear dependence on the position of FEA, i.e., the recombination lifetime increases with decreasing strain in the layers. We discuss the results in term of the hole states involved in the donor-bou nd exciton recombination. (C) 2001 American Institute of Physics.