Teilprojekt A2 "Lineare Stressorstrukturen" im Sonderforschungsbereich 787: "Nanophotonik: Materialien, Modelle, Bauelemente" (Sprecherhochschule TU Berlin)

The project aims at the advancement of the buried-stressor approach for fabricating (1) stripes of InGaAs- based carrier-localization layers for novel photonic devices and (2) single site-controlled long-wavelength QDs for fiber based quantum communication at telecom wavelengths; in addition, (3) device heterostructures will be developed and grown for other CRC projects.

1. Active waveguide structures with a high density of Stranski-Krastanow quantum dots (SK QDs) and sub- monolayer (SML) depositions aligned in linear arrays will be developed. Target is the fabrication of efficient edge-emitting devices, LD/SOA based on SK QDs and SML depositions, and waveguide photodetectors with SK QDs, employing single and multiple layers of stressor-induced stripe formation - adapted to the optical mode. The active region of these devices hence shall be fabricated employing a self-aligned site control of either quantum dots or SML depositions.

Benefits of the buried-stressor approach for ridge-waveguide devices are:

• The active low-Eg medium is vertically and laterally embedded in a high-Eg matrix
• The structures are fabricated in a self-aligned bottom-up approach, without post-growth processing
• Low absorption losses, lateral index guiding, low noise (in detector applications)

 Single site-controlled long-wavelength InGaAs QDs will be developed for single-photon sources operating at telecom wavelengths. The approach will apply the successful CRC phase-2 concept of buried stressors and additional pathways for emission red-shift like QD ripening and SRL overgrowth.
Epitaxy for energy-efficient high-bandwidth VCSELs based on SK-QDs, QWs, and SML structures pro- cessed in project C1 will also be performed. Devices will be designed for operation at 980 to 1240 nm emission wavelength required for short-range applications and silicon photonics. Furthermore, A2 will perform epitaxy of heterostructures with self-assembled InGaAs QDs emitting in the 900-980 nm spectral range for deterministic single-photon devices and integrated waveguide structures in C12.