Berlin 2005 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 45: Quantenpunkte und -dr
ähte: Transporteigenschaften II

HL 45.8: Vortrag

Montag, 7. März 2005, 16:45–17:00, TU P-N202

Determination of electron and hole localization in InAs/GaAs quantum dots via direct observation of tunneling escape — •Martin Geller, Erik Stock, Christian Kapteyn, Roman Sellin, and Dieter Bimberg — Institut für Festkörperphysik, TU Berlin, Hardenbergstr. 36, D-10623 Berlin

We have determined the tunneling barrier height, which is equal to the entire ground state localization energy, for electrons and holes in InAs/GaAs quantum dots (QDs). For the first time this important value was obtained by measuring the tunneling time constant as function of an applied external electric field in time resolved capacitance measurements. Previously, we had shown that time resolved capacitance spectroscopy (DLTS) is a powerful tool to study thermal emission processes and thermal activation energies in QDs. However, for electrons - but also for holes - the competing tunneling process in an applied electric field makes it impossible to measure directly the localization energy. In fact, for electrons only the quantization energy can be derived, due to tunneling through the tip of the triangular barrier, and the hole localization energy is always underestimated. With this new developed method via direct observation of tunneling escape in capacitance transients, the obtained localization energy is 240 meV for the electrons and 190 meV for the holes. These values are in very good agreement with our predictions from 8-band k·p calculations. The work was funded by the SANDiE Network of Excellence of the European Commission, contract number NMP4-CT-2004-500101 and SFB 296 of DFG.