Self-assembled InAs/GaAs quantum dots under resonant excitation

Abstract

The energy structure and the carrier relaxation in self-assembled InAs/GaAs quantum dots (SADs) is investigated by photoluminescence excitation spectroscopy (PLE) and photoluminescence (PL) at resonant excitation (below the GaAs and the wetting layer bandgap). In PLE measurements we find a clear resonance from the first excited hole state as well as resonances from a relaxation via different phonons. From a comparison of the PL-rise times in time resolved spectroscopy, we conclude on a fast electron relaxation (⩽50 ps) and a slow hole relaxation with a time constant of about 400 ps. Different relaxation paths are observed in the InAs/GaAs quantum dot system and allow us to identify the hole relaxation in the SADs as multiphonon assisted tunneling. The PL-decay time in the SADs after resonant excitation (about 600 ps) is attributed to the lifetime of the quantum dot exciton. In agreement with theoretical predictions, we find a constant lifetime of about 600 ps for temperatures below 50 K and a linear increase of the lifetime between 50 and 100 K with a slope of 26 ps/K.

Temperature dependent high resolution resonant spectroscopy on a charged quantum dot

“…The simple Bose-Einstein type model successfully describes the temperature evolution of interband transitions of bulk semiconductors as well as QDs [21,23,24]:…”

Structural and optical properties of low-density and In-rich InAs∕GaAs quantum dots

“…This type of behavior has already been reported and interpreted. [37][38][39] The temperature independence of the lifetime between 10 and 150 K ͑Ref. 40͒ is a consequence of the quantized energy structure.…”

Carrier transport in self-organizedInAs∕GaAsquantum-dot structures studied by single-dot spectroscopy

“…In fact, the biexciton should appear when the carrier generation rate into the dot exceeds the exciton recombination rate, which has been reported to be ͑600 ps͒ −1 = 1.7ϫ 10 9 s −1 for InAs/ GaAs QDs. 25 One can then express ␣ as…”