The growth of the III-V semiconductors was carried out by metal-organic vapour-phase epitaxy. The use of exactly oriented Si(001) substrates ensured that the device was compatible with established CMOS processing schemes.

Sample fabrication

First, the team deposited a GaAs-based buffer structure, with the aim to reduce the number of defects resulting from heteroepitaxial growth. The active zone of the emitter was built up of InP quantum dots embedded in AlGaInP. The latter serves as barrier material, providing efficient capture of charge carriers and radiative recombination up to elevated temperatures. For electrical excitation of the quantum dots, the structure was placed in the intrinsic zone of a pin-diode.

In detailed studies, the researchers investigated the structural and optical characteristics of the quantum dots. Spatially and spectrally resolved cathodoluminescence measurements revealed the distribution of the emission centres.

Red spectral region

Both optically and electrically pumped structures showed emission up to room temperature, at a wavelength around 650 nm. The team performed quantum optical measurements on single quantum dots, revealing the typical non-classical emission characteristics of a zero-dimensional emitter. The emission of single photons could be proven even up to 80 K. Therefore, the team concludes, InP/AlGaInP quantum dots on silicon may serve as single-photon sources for quantum optical applications or to build up the active zone of semiconductor lasers with superior performance.

Full details can be found in the journal Nanotechnology.