Berlin 2005 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 36: Quantenpunkte und -dr
ähte: Optische Eigenschaften III
HL 36.3: Vortrag
Montag, 7. März 2005, 10:30–10:45, TU P164
Photoluminescence studies of multi-modal self-assembled quantum dots under high hydrostatic pressure — •Christian Kristukat1, Alejandro Rudolfo Goñi2, Konstantin Pötschke1, Andrei Schliwa1, Dieter Bimberg1, and Christian Thomsen1 — 1Technische Universität Berlin, Institut für Festkörperphysik, PN 5-4, Berlin, Germany — 2ICREA Research Professor, Institut de Ciència de Materials de Barcelona, Campus de la UAB, 08193 Bellaterra, Spain
We have investigated the photoluminescence from self-assembled InAs/GaAs quantum dots at 2 K under high hydrostatic pressure up to 9 GPa. The spectra show up to nine peaks which are attributed to the ground-state exciton emission from groups of quantum dots which differ by entire monolayers. With increasing pressure all emission peaks shift to higher energy, exhibiting the typical behavior of direct Γ−Γ transitions. Beginning at about 4.6 GPa the emission of the smallest dots first and then that of the bigger dots quenches successively. At 9 GPa all peaks have disappeared. This is due to the conduction band crossover of the GaAs X-point energy with the Γ-point ground state of the dots, at which the electron confinement is lost and the heterostructure becomes type-II in character. The pressure coefficient of the exciton recombination in the dots varies from 66 meV/GPa up to about 100 meV/GPa for the largest and the smallest dots, respectively, which is in average much smaller than that of bulk GaAs and InAs. The reason for that are possibly the change of the misfit strain and the elastic constants with pressure which affects the band gap and the pressure dependence of the barrier height, effective masses and dot size which determine the confinement energy.