Improved size uniformity of InAs quantum dots grown on a lateral composition modulated InGaAs surface

The properties of InAs quantum dots (QDs) deposited on compositionally homo genous and laterally modulated surfaces is investigated by photoluminescenc e (PL), atomic force microscopy (AFM), and transmission electron microscopy . We use solid source molecular beam epitaxy on (100)-oriented InP substrat es to fabricate the samples. It is found that QDs grown on a laterally modu lated surface are more uniform in size. This is implied by a decrease of 22 % in the full width at half maximum (FWHM) in the PL signal at 77 K for InA s QDs deposited on the modulated surface as opposed to the homogenous surfa ce for equal monolayer coverage of InAs. Similarly, plan view scans taken b y ex situ contact AFM also show improved size uniformity of QDs grown on th e laterally composition modulated surface as evidenced by a decrease in the standard deviation of area data compiled from the images. It is shown that the improvement in the geometrical uniformity of the quantum dots as depic ted by the PL FWHM and AFM data is facilitated by an early onset of size se lf-equalization due to the lateral composition modulation. (C) 1999 America n Vacuum Society. [S0734-211X(99)04003-2].