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

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  • Bhavtosh Bansal
  • Stefanie Godefroo
  • Manus Hayne
  • Gilberto Medeiros-Ribeiro
  • Victor Moshchalkov
Article number205137
<mark>Journal publication date</mark>18/11/2009
<mark>Journal</mark>Physical review B
Issue number20
Publication StatusPublished
<mark>Original language</mark>English


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.

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©2009 The American Physical Society