Quantum dots: promises and accomplishments

Exploration of the Stranski-Krastanow growth of strained semiconductor hetero structures marked the major breakthrough for easy fabrication of defect-free quantum dots (QDs). For the first time, single QDs are facilitating the development of electrically operated emitters of single polarized or entangled photons on demand: an essential component for quantum communication systems. QDs inserted in quantum wells, stacked in planes upon each other, have led to semiconductor lasers that can operate at wavelengths that were previously impossible, or at least difficult to reach, for a given semiconductor family. These lasers show excellent temperature stability, large radiation resistance, and excellent temporal and spatial stability. In this review we discuss recent progress in the field of quantum dot devices.