3D AFM image of uncapped InAs QDs grown on an InGaAs/InP matrix.
An example of the virtually simultaneous complementary spectroscopic measurements on the InAs/InGaAs/InP QDs: (a) 150 K PL spectrum along with a least-square fits (full curve) using two Gaussian components (shown separately by dotted curves), (b) 150 K PR spectrum, and (c) 150 K SPS spectrum. The vertical dotted lines correlate the individual components seen in three spectra.
The temperature dependent PL spectra of the InAs/InGaAs/InP QDs. The numbers next to each spectrum show the intensity magnification factors.
Least-squares fits (full curves) of PL spectra at (a) 9 K with single Gaussian component, (b) 150 K with two Gaussian components, and (c) 200 K with three Gaussian components, with the individual components shown by the dotted curves.
Results of fitting the temperature dependent PL spectra, showing: (a) PL peak position, (b) FWHM, and (c) integrated PL intensity vs temperature. The circles, squares, and triangles are for transitions GS, , and , respectively. The full curve in (a) is a fit for transition energy GS with BE relation, i.e., Eq. (1) while the other lines are only guides to the eyes.
Example SPS spectra of the InAs/InGaAs/InP QDs at three representative temperatures.
(a) Least-squares fits of the SPS spectrum at 100 K with a single Gaussian peak along with Urbach tail. (b) The same fitting exercise at four temperatures shown with the Urbach tail removed for clarity in presentation.
A comparison of the QD transition energies determined by the PL and SPS measurements as a function of temperature. The dotted line is only a guide to the eyes. The large error bar for the SPS result at 200 K is due to uncertainty in fitting. The errors in the other SPS results are smaller than the symbol size. The full curve is as in Fig. 5(a).
Example PR spectra of the InAs/InGaAs/InP QDs at three representative temperatures. The full curves show FDLL fits using Aspnes line shape function, i.e., Eq. (2) with four oscillators.
Detail of the fit shown in Fig. 9 for the 150 K PR spectrum. The four individual FDLL components are shown by the dotted curves.
A comparison of the transition energies determined by the PL and PR measurements as a function of temperature. The dotted lines are only a guide to the eyes. The full curve is as in Fig. 5(a).
A summary of the full set of results showing the QD transition energies determined by the three virtually simultaneous complementary PL, PR, and SPS techniques. The transition energy vs temperature results are fitted using BE relation, i.e., Eq. (1) as shown by the solid curves. The uncertainties in the fitted energies are all smaller than or comparable to the sizes of the respective symbols, except in the case of the 200 K SPS result where the large dotted error bar is due to uncertainty in fitting.
Layer structure details for the InAs/InGaAs/InP QD sample investigated in the present work. The nominal thickness and composition of InGaAs barrier layer is given in the table. The indium content of the barrier layer increases from 0.53 to 0.72 when one approaches the QD layer from either side, as shown in the table.
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