InAs/GaAs(100) self-assembled quantum dots: Arsenic pressure and capping effects

We explore growth effects leading to size and compositional limitations in the production of self-assembled quantum dots (QD) emitting at long wavelengths. Molecular beam epitaxy grown QDs are studied as a function of arsenic pressure at a specific InAs coverage, and as a function of InAs coverage for three arsenic pressures. As a function of increasing the arsenic pressure used in QD growth, the photo luminescence (PL) of capped QDs is first redshifted at low arsenic pressures, and then blueshifted at high arsenic pressures. Microscopy of uncapped QDs shows that as the arsenic pressure increases, the QD density increases while the average QD width and height decrease monotonically; these trends are consistent with the shift in PL for the high arsenic pressure samples, but are inconsistent with the shift in PL for the low-pressure samples. This points to a modification of the QDs during capping. We discuss prior reports pertaining to arsenic pressure and capping effects, and in this context describe our observations of the effects of adjusting the arsenic pressure on the formation of QDs and the mechanism by which QDs may be modified during capping. (C) 2002 Elsevier Science B.V. All rights reserved.