Band alignment and carrier recombination of InAs/GaAs<sub>1?</sub><sub><italic>x</italic></sub>Sb<sub><italic>x</italic></sub> quantum dots affected by Sb content

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SCIENTIA SINICA Physica, Mechanica & Astronomica
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SCIENTIA SINICA Physica, Mechanica & Astronomica, Volume 48, Issue 10: 107301(2018) https://doi.org/10.1360/SSPMA2018-00227

Band alignment and carrier recombination of InAs/GaAs1?xSbx quantum dots affected by Sb content

Lian JI1,*, Sai YE1, ShuLong LU2
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  • ReceivedJun 12, 2018
  • AcceptedJul 4, 2018
  • PublishedSep 6, 2018
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Abstract

The influences of Sb content on the band structure and carrier recombination dynamics of InAs/GaAs1?xSbx quantum dots (QDs) have been investigated by both calculation and experimental demonstration. The calculation results using the eight-band model indicated that the band alignment of InAs/GaAs1?xSbx QDs was type I at low Sb content and changed from type I to type II when Sb content increased from 0.08 to 0.14. During this phase, electrons were still localized in InAs QDs while holes were transferred from InAs QDs to the GaAsSb capping layer gradually, which resulted in the reduction of the overlap of electron and hole wave functions and carrier transition rate. To experimentally prove the calculation results, InAs/GaAs1?xSbx QDs with various Sb contents were grown by molecular beam epitaxy. The photoluminescence (PL) measurement results confirmed the expected influence of Sb content on the band alignment of InAs/GaAs1?xSbx QDs. For InAs/GaAs1?xSbx QDs samples with Sb content of 0.15 and 0.2, the PL peak energy showed a blue shift with increasing excitation power, which is a signature of a type-II band alignment structure. On the other hand, the PL peak energy was independent of excitation power in the samples with Sb content of 0.05 and 0.1. Besides, the redshift with increasing Sb content became stronger and the PL intensity became weaker when Sb content was larger than 0.14. To investigate the carrier transition rate, time-resolved PL measurement was performed. The minority carrier lifetime increased from 0.41 to 14.3?ns when the band alignment of InAs/GaAs1?xSbx QDs changed from type I to type II, which indicated that carrier recombination was inhibited. InAs/GaAs1?xSbx QDs with type-II band alignment are preferred for intermediate band solar cells due to longer carrier lifetime resulting from the spatial separation of electrons and holes, which is beneficial to maintain the separation between conduction band, intermediate band and valence band quasi-Fermi levels.


Funded by

国家自然科学基金(批准号:)


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