Extended excitons and compact heliumlike biexcitons in type-II quantum dots.

Bansal, Bhavtosh and Godefroo, Stefanie and Hayne, Manus and Medeiros-Ribeiro, Gilberto and Moshchalkov, Victor (2009) Extended excitons and compact heliumlike biexcitons in type-II quantum dots. Physical review B, 80 (20). ISSN 1098-0121

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We have used magneto-photoluminescence measurements to establish that InP/GaAs quantum dots have a type-II band (staggered) alignment. The average excitonic Bohr radius and the binding energy are estimated to be 15 nm and 1.5 meV respectively. When compared to bulk InP, the excitonic binding is weaker due to the repulsive (type-II) potential at the hetero-interface. The measurements are extended to over almost six orders of magnitude of laser excitation powers and to magnetic fields of up to 50 tesla. It is shown that the excitation power can be used to tune the average hole occupancy of the quantum dots, and hence the strength of the electron-hole binding. The diamagnetic shift coe±cient is observed to drastically reduce as the quantum dot ensemble makes a gradual transition from a regime where the emission is from (hydrogen-like) two-particle excitonic states to a regime where the emission from (helium-like) four-particle biexcitonic states also become significant.

Item Type:
Journal Article
Journal or Publication Title:
Physical review B
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©2009 The American Physical Society
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Deposited On:
09 Dec 2009 10:57
Last Modified:
14 Sep 2023 23:46