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HL: Fachverband Halbleiterphysik

HL 13: Quantum Dots and Wires: Preparation and Characterization I

HL 13.3: Vortrag

Montag, 22. März 2010, 14:30–14:45, H17

Improvement of the optical quality of site-controlled InAs quantum dots by a double stack growth technique in wet-chemically etched holes — •Tino Johannes Pfau¹, Aleksander Gushterov¹, Johann-Peter Reithmaier¹, Isabelle Cestier², Gadi Eisenstein², Evgany Linder³, and David Gershoni³ — ¹Technische Physik, INA, Universität Kassel, 34132 Kassel — ²Electrical Engineering Dep., Technion, Haifa 32000, Israel — ³Solid State Institute and Physics Dep., Technion, Haifa 32000, Israel

The optimization of the wet-chemically etching of holes and a special MBE growth stack technique allows enlarging the site-control of low density InAs QDs on GaAs substrates up to a buffer layer thickness of 55 nm [1]. The strain of InAs QDs, grown in the etched holes, reduces the hole closing, so that a pre-patterned surface is conserved for the second QD layer. The distance of 50 nm GaAs between the two QD layers exceeds drastically the maximum vertical alignment based on pure strain coupling (20 nm). Compared to stacks with several QD layers, this method avoids electronic coupling between the different QD layers and reduces the problems to distinguish the dots of different layers optically. Confocal microphotoluminecence reveals a significant diminution of the low temperature photoluminescence linewidth of the second InAs QD layer to an average value of 505 ± 53 µ eV and a minimum width of 460 µ eV compared to 2 to 4 meV for QDs grown on thin buffer layers. The increase of the buffer layer thickness decreases the influence of the surface defects caused by prepatterning.
T. J. Pfau, et al., Appl. Phys. Lett. 95 (2009)