ABSTRACT
Self-assembled Ge wires with a height of only 3 unit cells and a length of up to 2 micrometers were grown on Si(001) by means of a catalyst-free method based on molecular beam epitaxy. The wires grow horizontally along either the [100] or the [010] direction. On atomically flat surfaces, they exhibit a highly uniform, triangular cross section. A simple thermodynamic model accounts for the existence of a preferential base width for longitudinal expansion, in quantitative agreement with the experimental findings. Despite the absence of intentional doping, the first transistor-type devices made from single wires show low-resistive electrical contacts and single-hole transport at sub-Kelvin temperatures. In view of their exceptionally small and self-defined cross section, these Ge wires hold promise for the realization of hole systems with exotic properties and provide a new development route for silicon-based nanoelectronics.
ABSTRACT
We integrate resonant-cavity light-emitting diodes containing quantum dots onto substrates with giant piezoelectric response. Via strain, the energy of the photons emitted by the diode can be precisely controlled during electrical injection over a spectral range larger than 20 meV. Simultaneously, the exciton fine-structure-splitting and the biexciton binding energy can be tuned to the values required for entangled photon generation.
