Effects of interface-layers composition and strain distribution on the optical transitions of InAs quantum dots on InP

In the present work we have investigated the optical properties of the self-assembled quantum dots (SAQD's) on an InP substrate. The dots are grown by gas source molecular-beam epitaxy (GSMBE) and characterized by photoluminescence (PL) and atomic force microscopy. The energy of the fundamental optical transitions measured by PL present a redshift compared to calculated values. Two hypotheses have been tested to explain this apparent difference: the existence of an intermediate InAsyP_1-y layer, with a composition depending on the experimental conditions, changes the value of the transition energy, and the strain induced in the InP confinement barrier by the dot as pointed out by Tersoff, has the same effect. The present study concludes with a discussion of the presence of a thin InAsyP_1-y interface layer originating from As/P exchange kinetic energy at the second interface on top of the dots.