Self-assembled PbSe quantum dot superlattices: Ordering and device applications

Self-organized lateral and vertical ordering in PbSe/Pb1-xEuxTe quantum dot superlattices results in the formation of three differently ordered dot phases. For thin PbEuTe spacers, the dots are vertical aligned with a weak hexagonal lateral ordering, for intermediate spacer thicknesses, a fcc-stacking with nearly perfect hexagonal lateral ordering is observed, and for thick spacers, uncorrelated and disordered superlattices are formed. The experimental data can be represented in a phase diagram, showing that in the different regimes a qualitatively different scaling behavior of the lateral dot distances versus spacer thickness occurs. For applications, we have inserted the PbSe quantum dot superlattice into the active region of a EuTe/PbEuTe vertical microcavity structure. From this structure, narrow laser emission at 4.2-3.9 mum induced by optical pumping is achieved at temperatures up to 90 K.