Dresden 2009 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 39: Quantum dots: Optical and transport properties

HL 39.11: Talk

Thursday, March 26, 2009, 12:30–12:45, BEY 81

Enhanced performance of a quantum dot based memory device with selective band engineering — •Johannes Gelze¹, Andreas Marent¹, Tobias Nowozin¹, Martin Geller², and Dierter Bimberg¹ — ¹Institut für Festkörperphysik, TU-Berlin, Hardenbergstraße 36, 10623 Berlin — ²Department of Physics and CeNIDE, University of Duisburg-Essen, Lotharstraße 1, 47048 Duisburg

Recently, we have introduced a novel memory concept (QD-Flash) based on self-organized quantum dots (QDs) providing much better performance than nowadays Flash-memory. For InAs/GaAs-QDs we have demonstrated a write time of 6 ns. With an additional Al0.9Ga0.1As barrier, a hole storage time in InAs/GaAs-QDs of 1.6 s at 300 K were shown. The erase process in the QD-Flash is realized by tunnelling through the confining potential in an electric field. Both, storage time and erase time are determined by the activation energy of the charge carriers. Thus, a trade-off exists between storage time and erase time. To reduce this trade-off, we have investigated the influence of more complex barriers below the QDs by simulating the carrier emission rate, using a WKB-Method. Barriers are designed having a much higher emission rate for a given activation energy than originally used triangular barriers. To confirm these results we studied the influence of Al0.6Ga0.4As and Al0.9Ga0.1As barriers on the write/erase times of the QD-Flash by capacitance-voltage measurements. A reduction of the erase time in a good agreement with the simulation was observed, keeping the write time below 10 ns.