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Stranski–Krastanov InAs/GaAsSb quantum dots coupled with sub-monolayer quantum dot stacks as a promising absorber for intermediate band solar cells

BaC6

Wednesday, November 22, 2017

The optical properties of the Stranski–Krastanov (S–K) grown InAs/GaAsSb quantum dots (QDs) coupled to sub-monolayer (SML) InAs QD stacks are investigated using photoluminescence (PL) spectroscopy. The PL emission peak of the S–K QDs shifts to shorter wavelengths with increasing the number of SML stacks (N_SML) due to the increasing strain fields from the SML QDs. The PL peak energy is linearly increased with increasing the cube root of excitation power, with a different ratio of the absorption coefficient to radiative recombination rate for all the QD samples. The total carrier lifetime for the S–K QDs is increased with increasing N_SML, most probably caused by the increase in the ground-state transition energy of the S–K QDs. The nonmonotonic behavior of the thermal activation energy of electrons in the S–K QDs is observed due to the N_SML-dependent variation of the strain and Coulombic interaction within the QDs.

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