Dresden 2003 – scientific programme

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HL: Halbleiterphysik

HL 48: Quantenpunke und -dr
ähte: Transporteigenschaften III

HL 48.4: Talk

Thursday, March 27, 2003, 16:00–16:15, BEY/81

Admittance spectroscopy of electrons and hole in self- organized InAs/GaAs quantum dots — •Erik Stock, Martin Geller, Roman Sellin, Christian Kapteyn, Robert Heitz, and Dieter Bimberg — Institut für Festkörperphysik, TU Berlin, Hardenbergstr. 36, D-10623 Berlin

We study the emission processes of electrons and holes by admittance spectroscopy and capacitance transient spectroscopy in comparable samples of self-organized quantum dots. The samples consist of GaAs p⁺n and n⁺p diodes with InAs quantum dots embedded. The differential conductance of such structures depends on the balance between the measurement frequency and the emission rate of the carriers from the quantum dot. By increasing the reverse bias voltage we carried out quasi-static capacitance-voltage measurements for decreasing effective Fermi-level in the quantum dots. The observed activation energy for the electrons decreases from about 110 meV to 30 meV exhibiting a pronounced step between 70 meV and 50 meV. This step is probably related to the electron level splitting between ground and excited states. The activation energy for the holes on the other hand decreases quasi-continuously from about 120 meV to 60 meV, which reflects the significantly smaller level splitting energy.

This work was funded by the Nanomat project of the European Commission Growth Programme, contract number G5RD-CT- 00545, INTAS project 2001-774, and SFB 296 of DFG