12,000

We have over 12,000 students, from over 100 countries, within one of the safest campuses in the UK

93%

93% of Lancaster students go into work or further study within six months of graduating

Home > Research > Publications & Outputs > Blueshifts of the emission energy in type-II qu...
View graph of relations

« Back

Blueshifts of the emission energy in type-II quantum dot and quantum ring nanostructures

Research output: Contribution to journalJournal article

Published

Article number073519
Journal publication date21/08/2013
JournalJournal of Applied Physics
Journal number7
Volume114
Number of pages7
Original languageEnglish

Abstract

We have studied the ensemble photoluminescence (PL) of 11 GaSb/GaAs quantum dot/ring (QD/QR) samples over >= 5 orders of magnitude of laser power. All samples exhibit a blueshift of PL energy, Delta E, with increasing excitation power, as expected for type-II structures. It is often assumed that this blueshift is due to band-bending at the type-II interface. However, for a sample where charge-state sub-peaks are observed within the PL emission, it is unequivocally shown that the blueshift due to capacitive charging is an order of magnitude larger than the band bending contribution. Moreover, the size of the blueshift and its linear dependence on occupancy predicted by a simple capacitive model are faithfully replicated in the data. In contrast, when QD/QR emission intensity, I, is used to infer QD/QR occupancy, n, via the bimolecular recombination approximation (I alpha n(2)), exponents, x, in Delta E alpha I-x are consistently lower than expected, and strongly sample dependent. We conclude that the exponent x cannot be used to differentiate between capacitive charging and band bending as the origin of the blueshift in type-II QD/QRs, because the bimolecular recombination is not applicable to type-II QD/QRs. (C) 2013 AIP Publishing LLC.