The photoluminescence (PL) of InAs/GaAs heterostructures is investigated for InAs coverages, L, ranging from 0.6 to 3 monolayers (ML). For thin coverages (L ≤ 1.6 ML), we observe the recombination of heavy-hole excitons in InAs quantum dots (QDs) and in a 2D-InAs layer. The two PL bands shift toward low energy for increasing L. For L ≤ 1.6 ML, the QD band shifts faster, while the exciton recombination in the 2D-layer vanishes. These results, confirmed by PL excitation and photoreflectivity, indicate that: a) QDs are interconnected by a two-dimensional InAs layer which allows an efficient carrier capture into the dots; b) the dot size increases with L, faster for L ≤ 1.6 ML, at the expense of the 2D-layer. The peculiar temperature dependence of lineshape and peak energy of the QD band is explained in terms of exciton thermal escape and relaxation mechanisms.
EVOLUTION OF THE OPTICAL PROPERTIES OF INAS/GAAS QUANTUM DOTS FOR INCREASING INAS COVERAGES
GEDDO, MARIO;
1997-01-01
Abstract
The photoluminescence (PL) of InAs/GaAs heterostructures is investigated for InAs coverages, L, ranging from 0.6 to 3 monolayers (ML). For thin coverages (L ≤ 1.6 ML), we observe the recombination of heavy-hole excitons in InAs quantum dots (QDs) and in a 2D-InAs layer. The two PL bands shift toward low energy for increasing L. For L ≤ 1.6 ML, the QD band shifts faster, while the exciton recombination in the 2D-layer vanishes. These results, confirmed by PL excitation and photoreflectivity, indicate that: a) QDs are interconnected by a two-dimensional InAs layer which allows an efficient carrier capture into the dots; b) the dot size increases with L, faster for L ≤ 1.6 ML, at the expense of the 2D-layer. The peculiar temperature dependence of lineshape and peak energy of the QD band is explained in terms of exciton thermal escape and relaxation mechanisms.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
