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 $L\gtrsim 2$ 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.