Over 100 ns intrinsic radiative recombination lifetime in type II InAs/GaAs1−xSbx quantum dots

Abstract

We report very long intrinsic radiative recombination lifetime τrad in type II InAs quantum dots embedded in GaAs1−xSbx. The dependence of photoluminescence (PL) decay time τPL on both the Sb composition (x = 0–0.18) and excitation intensity (38–460 mW/cm2) was systematically investigated by time-resolved PL measurements with a time-correlated single-photon counting method. All PL decay curves exhibited non-exponential profiles, and τPL was strongly dependent on the excitation intensity. These properties were well explained by solving rate equations of carrier density with neglecting nonradiative process, in which τrad is inversely proportional to carrier density. The 18% Sb sample exhibited a τPL of over 100 ns under weak excitation, which is longer than twice the previously reported values. We evaluated the value of τrad in InAs/GaAs1−xSbx QDs relative to that in type I InAs/GaAs QDs based on an effective mass approximation and found that the observed extremely long τPL corresponds to τrad.

Extremely long carrier lifetime over 200 ns in GaAs wall-inserted type II InAs quantum dots

“…The detailed discussion of the carrier dynamics in InAs/ GaAs 1Àx Sb x type II QDs is to be reported elsewhere. 19 To find the effect of the GaAs walls, we show PL decay curves for the three samples in Fig. 4, which were measured at the peak energies of the PL spectra, respectively.…”

Extremely long carrier lifetime at intermediate states in wall-inserted type II quantum dot absorbers

“…6(b), which is remarkably longer than previously reported values, 14 due to the low carrier density. 15 The value for the wall-inserted type II sample is more significantly extended up to t ¼ 60 ns to be as long as 220 ns. Our new concept realized an extremely long s ðIBÞ e ðtÞ.…”

“…This remarkably suppresses the recombination of electrons and holes and realizes a long lifetime of photo-excited electrons in the IB. 14,15 To further extend the lifetime, we propose to insert potential walls between the QDs and barrier material.…”

“…The experimental details are described elsewhere. 15 A liquid helium cryostat was used to keep the sample at 4 K.…”

Recent Research Activities for Future Challenges in Global Energy and Environment in Toyota Central R&D Labs., Inc. (TCRDL)

“…The third generation solar cells such as (1) hot-carrier type, (2) multi-exciton generation type, and (3) intermediateband type have been proposed to decrease the loss mentioned above without using solar concentrators. We have also studied these solar cells both theoretically 27 " 32 and experimentally 33 ' 34 . Spontaneous formation and arrangement of quantum dots is a key factor in these solar cells.…”