Optical Detection of the Charging of InAs Quantum Dots with Different Backgate Configurations
- PDF / 284,250 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 6 Downloads / 170 Views
E16.2.1
Optical Detection of the Charging of InAs Quantum Dots with Different Backgate Configurations B. Su, L. Karsten, C. Schüller, D. Heitmann, A. A. Zhukov, Ch. Heyn, and W. Hansen Institut für Angewandte Physik und Zentrum für Mikrostrukturforschung, Universität Hamburg, Jungiusstraße 11, 20355 Hamburg, Germany ABSTRACT We investigate self-assembled InAs quantum dots by photoluminescence (PL) and capacitance spectroscopies. By employing specially designed backelectrode configurations, we can control the number of electrons, which are confined in the quantum dots. With PL experiments we study the dependence of the s-s transition on the electron occupation of the quantum dots. We observe a characteristic redshift of the s-s transition when the s-shell is filled with electrons. However, if the p-shell of the quantum dots starts to fill, the samples with different backelectrode configurations show a different behavior. In one type of samples, the signal stays redshifted, while in the other it blueshifts again. The effect can be explained by different hole capture processes in both types of samples.
INTRODUCTION The optical properties of charge carriers, confined in semiconductor quantum dots, have attracted great research interest during the past decade [1]. This is because these systems are both, from a technological as well as from a fundamental physics point of view, very attractive. In particular, the Coulomb correlations of few charge carriers, confined in small quantum dots, can be profoundly affected by the three-dimensional confinement. Therefore, the controlled charging of quantum dots with single electrons is a powerful means to study these effects in detail. In lithographically defined quantum dots of few hundreds nanometer size, the charging by single electrons was demonstrated already one decade ago [2]. In recent years, self-assembled InAs quantum dots (SAQD) have become very attractive, since they are small in size (typically 20 nm diameter), and the controlled charging by single electrons could be demonstrated [3]. Subsequently, a variety of optical investigations, like transmission [4,5] or photoluminescence (PL) experiments (e.g., Refs. [6,7]) followed, which demonstrated the impact of few-electron charged states in the quantum dots on their optical properties. Very recently, also in PL experiments on single objects, the controlled charging of quantum dots [8,9] or quantum rings [10] was demonstrated, using external gates [8,10] or optical depletion [9]. Interesting interaction effects have also been revealed in multi-exciton experiments on single [11] or tunneling-coupled InGaAs double dots [12]. Even the control of the electronic and nuclear spins was demonstrated [13,14], and Rabi oscillations were detected [15] in experiments on single dots. In this contribution, we report on the investigation of InAs SAQD, which are embedded between two gate electrodes, by PL and capacitance (C-V) measurements. In order to be able to charge the quantum dots with single electrons, we have grown specially des
Data Loading...
