Optically-induced charge storage in self-assembled InAs quantum dots

We present results on spectrally resolved photo-resistance studies of optic ally-induced charge storage effects in self-organized InAs quantum dots (QD s). The stored charge can be detected and erased electrically. The investig ated structure designed for electron or hole storage in the QDs consists of a modulation doped two-dimensional channel which was grown on top of a lay er of InAs QDs, separated by an asymmetric tunnel barrier. Our results show that optical QD charging with spectral resolution provides information on the charging dynamics and on the quantity and spectral dependence of stored charges in the QDs. This is a novel technique by which QD excitation spect ra can be studied. Spectrally resolved storage effect measurements on elect rons as well as on holes allowed to investigate thermal redistribution of c arriers in the quantum dot layer. It was found that only at low temperature s carriers can be stored selectively over long time scales in the InAs QDs. The charge storage effect is observable for several hours at temperatures up to 170 K, for several seconds up to 250 K due to an increase in thermal emission of stored charges. (C) 2000 Elsevier Science B.V. All rights reser ved.