Optical properties of InAs quantum dots: Common trends

We compare results obtained in several tens of samples grown by molecular-beam epitaxy under different growth conditions with a substantial amount of data found in the literature. By plotting the photoluminescence (PL) peak energy (E-p) of the quantum dot (QD) bands as a function of the nominal thickness of deposited InAs (L) three regions are clearly evidenced in the (E-p,L) plane. Below the so-called critical thickness (L-c), three-dimensional precursors of QD's show a smooth dependence of their emission energy on L. Around L-c, QD's show a steep dependence of E-p on L, independent of the growth conditions. Finally, for L greater than or similar to 2 ML one observes a saturation of the PL energy. This energy assumes only discrete values dependent on the growth conditions, which is attributed to the aggregation of quantum dots with different faceting.