Dresden 2006 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 46: Quantum dots and wires: Preparation and characterization II

HL 46.1: Vortrag

Donnerstag, 30. März 2006, 15:15–15:30, POT 51

Charge-State and Magnetic-Field Dependence of Electron Emission from self-assembled InAs quantum dots — •Andreas Schramm, Jan Schaefer, Stephan Schulz, Christian Heyn, and Wolfgang Hansen — Institut für Angewandte Physik, Jungiusstraße 11C, 20355 Hamburg

Using capacitance transient spectroscopy, we probe electron states in self-assembled InAs/GaAs quantum dots (QD). In our sample a single QD layer is embedded in a Schottky diode grown on (001) GaAs in a solid source MBE system. With a pulse bias applied at the gate we control the charge state of the QDs. The emission rate is found to be strongly dependent on the charge state. In the DLTS-spectra the peak associated to emission from the s-level is therefore split. Here we present data that demonstrate in addition fine structure in the maximum associated to the emission of p-electrons. We associate it to the emission of the four distinct charge states for p-electrons. To confirm our assignment of the DLTS-maxima we apply magnetic fields normal to the quantum dot layer. The observed behavior of the peak positions and the activation energies in the magnetic field is consistent with a harmonic oscillator model. Furthermore, in magnetic fields oriented parallel to the dot layer we clearly observe a suppression of tunneling processes.