EXCITONIC PHOTOLUMINESCENCE SPECTRA OF ALXGA1-XAS GROWN BY METALORGANIC VAPOR-PHASE EPITAXY

Excitonic transitions were measured in Al(x)Ga(1-x)As, grown by metalorganic vapor phase epitaxy (MOVPE), at two different alloy compositions using high resolution photoluminescence spectroscopy. The first observation is reported of an excitonic spectrum which is separated into neutral donor, ionized donor, and neutral acceptor bound exciton transitions [(D0,X), (D+,X), and (A0,X)] at an aluminum fraction higher than 20%. A significant decrease in linewidth of the (D0,X) peak is found by decreasing the excitation density and by decreasing the laser spot size. This means that the linewidths of the various excitonic transitions are, apart from alloy broadening, strongly dependent on both the long range Coulombic potentials of the ionized impurities in our samples, and on clustering effects. Finally, linewidths of 1.75 and 2.5 meV were measured for the (D0,X) transitions for samples with Al fractions of 0.12 and 0.244, respectively. These are the smallest values ever reported in literature for samples grown by MOVPE.