G. Martinez-criado et al., Optical characterization of Mg-doped GaN films grown by metalorganic chemical vapor phase deposition, J APPL PHYS, 88(6), 2000, pp. 3470-3478
Scanning electron microscopy, micro-Raman, and photoluminescence (PL) measu
rements are reported for Mg-doped GaN films grown on (0001) sapphire substr
ates by low-pressure metalorganic chemical vapor phase deposition. The surf
ace morphology, structural, and optical properties of GaN samples with Mg c
oncentrations ranging from 10(19) to 10(21) cm(-3) have been studied. In th
e scanning micrographs large triangular pyramids are observed, probably due
to stacking fault formation and three-dimensional growth. The density and
size of these structures increase with the amount of magnesium incorporated
in the samples. In the photoluminescence spectra, intense lines were found
at 3.36 and 3.31 eV on the triangular regions, where the presence of cubic
inclusions was confirmed by micro-Raman measurements. The excitation depen
dence and temperature behavior of these lines enable us to identify their e
xcitonic nature. From our study we conclude that the interface region betwe
en these defects and the surrounding wurtzite GaN could be responsible for
PL lines. (C) 2000 American Institute of Physics. [S0021-8979(00)07719-7].