ABSTRACT
Young Min Park, Young Ju Park*, Kwang Moo Kim, Jin Dong Song, and Jung II Lee Nano Device Research Center, Korea Institute of Science and Technology P.O. Box 131, Cheongryang, Seoul 130-650, Korea Corresponding author: yjpark@kist.re.kr
Abstract. We investigated the quantum-confined Stark effect (QCSE) in the self-assembled InAs quantum dots (QDs). The QDs are formed by the atomic layer molecular beam epitaxy (ALMBE) technique using alternately supplying InAs and GaAs sources. From the electric field dependent photoluminescence measurements, permanent dipole moment is estimated to p = (4.8±1.6)xl0‘29 Cm, indicating that QDs have a permanent dipole moment. This corresponds to the electron-hole separation of r = 3±1 A. 12
1. Introduction In recent years, self-assembled quantum dots (QDs) have gained considerable interest due to the fact that they can be regarded as ideal model systems permitting to study quasi zero-dimensional excitons.[l-3] Therefore, QDs are often referred to as “artificial atoms”. Many effects known from atomic physics were found in QDs. In particular, the quantumconfined Stark effect (QCSE) was recently claimed to be responsible for spectral diffusion, i.e., a rather random spontaneous shift of the luminescence energy in QDs. From a basic physics point of view, the QCSE can provide detailed insight into the charge distribution in the QDs. Recent experimental results [4,5] have shown that the Stark shift exhibits an asymmetry in the presence of an electric field, due to a built-in dipole moment. Theoretical studies [6,7] have shown that the sign of this dipole moment in single QD depends on the composition gradient and/or strain effect, localizing the electron and hole in different regions of the QD. Knowledge of the respective positions of electrons and holes can provide information on the confining potential experienced by both particles, which is of primary importance for fundamental as well as practical reasons. This inverted electron-hole alignment has been obtained experimentally by assuming the usual linear relation between the electric dipole moment and the Stark shift in QCSE spectroscopy. In this work, we performed photoluminescence (PL) for InAs QDs under electric field in order to study the QCSE. In result, it is shown that the QDs possess a permanent dipole moment, implying a finite spatial separation of the electron and hole.
