Field dependent carrier dynamics and charged excitons in InAs self-assembled quantum dots

We have used photocapacitance, photocurrent and photoluminescence spectroscopy to study the field-dependent dynamics and radiative recombination of optically excited electron-hole pairs in InAs self-assembled quantum dots (QDs) under various charging conditions. In the investigated field region the excitons relax into the ground state before tunneling or radiative recombination takes place. At high internal fields electrons and holes tunnel out of the QDs while at low fields the excitons recombine in the dot. In the low-field regime a red shift of the QD ground slate photoluminescence is observed when the QDs are loaded with electrons. A decrease in the overall intensity indicates a lower oscillator strength of charged excitons in InAs self-assembled QDs. Field effects being responsible for the observed energy shift can be excluded since the energetic position of the ground-state transition remains constant at high fields. (C) 1998 Elsevier Science B.V. All rights reserved.