Vertically stacked quantum dots grown by ALMBE and MBE

We report on a systematic study of InAs/GaAs self-aggregated quantum dot (Q D) structures grown by ALMBE and MBE, consisting of 1-11 QD layers and of s pacer layers with thicknesses of 20 - 53 ML. The AFM study of the topmost, uncapped layer of QDs shows that ALMBE structures are more ordered and have QDs with larger dimensions and with sharper size distributions than the MB E. counterparts. The energies and full-widths at half-maxima (fwhm) of 10 K photoluminescence (PL) transitions have been studied as functions of the n umber of stacked layers and of spacer thicknesses. We show that ALMBE allow s the growth of stacked-QD structures that have bright PL at RT, emission w avelengths at RT very close to the 1.3 mu m spectral window and 10 K fwhms as low as 22 meV. (C) 1999 Published by Elsevier Science B.V. All rights re served.