LOW-TEMPERATURE PHOTOLUMINESCENCE PROPERTIES OF INGAN FILMS GROWN ON (01(1)OVER-BAR2) AL2O3 AND (0001) AL2O3 SUBSTRATES BY LOW-PRESSURE MOVPE

Low temperature photoluminescence (PL) properties of InGaN films grown on (0 1 (1) over bar 2) Al2O3 and (0 0 0 1) Al2O3 substrates by low p ressure MOVPE were studied at 11 K. In the PL spectrum of a In0.11Ga0. 89N/AlN buffer/(0 1 (1) over bar 2)Al2O3 film, only one near band edge emission with wavelength 371.4 nm was observed in the range from 350 nm to 630 nm. For InxGa1-xN/GaN/GaN buffer/(0 0 0 1)Al2O3 films with x = 0.02 and 0.035, similar PL spectra of GaN films, the recombinations of an exciton bound to a neutral donor (I-2 lines) were observed and seem to be dominant. The peak energy positions were 3.467 eV, 3.454 eV and 3.449 eV for x = 0, 0.02 and 0.03, respectively. It was found tha t FWHM roughly increase as x increases. Donor-Acceptor (D-A) pair comb ination near 3.27 eV and their LO-phonon replica (near 3.18 eV) also a ppeared in the PL spectra. The LO-phonon energy of InxGa1-xN shift to high energy compared to GaN. It is suggested that the D-A pair recombi nation contributes to the transitions from a shallow donor to a carbon -related acceptor level. (C) 1997 Elsevier Science Ltd.