Quantum dots with coherent interfaces between rocksalt-PbTe and zincblende-CdTe

The formation of PbTe quantum dots (QDs) in a crystalline CdTe host matrix is demonstrated by the annealing of a coherent, heteroepitaxial PbTe layer clad between CdTe layers. The resulting QDs have a centrosymmetric shape and they exhibit intense room-temperature mid-infrared photoluminescence due to an electron-hole pair recombination in the narrow-gap PbTe. The intense luminescence approves the high quality of the QD interfaces, between the sixfold coordinated rocksalt structure of PbTe and the fourfold coordinated zincblende structure of CdTe. To gain further insight into the structural interface properties, we compare quantitatively multislice simulations of HRTEM images with first-principles total-energy calculations in the repeated-slab approximation. The most drastic effect occurs at the electrostatically neutral (110) interface, where we find a lateral spatial offset between the two crystal halves due to rebonding across the interface. For the two polar (001) interfaces, significantly different lattice plane spacings are observed, depending on whether the polar CdTe (001) face is cation or anion-terminated. The agreement between the first-principles calculations and the HRTEM data is excellent.