Self-Aligned Photonic Defect Microcavity Lasers with Site-Controlled Quantum Dots

Self-assembled semiconductor quantum dots face challenges in terms of scalable device integration because of their random growth positions, originating from the Stranski-Krastanov growth mode. Even with existing site-controlled growth techniques, for example, nanohole or buried stressor concepts, a further lithography and etching step with high spatial alignment requirements is necessary to accurately integrate quantum dots into the nanophotonic devices. Here, the fabrication and characterization of strain-induced site-controlled microcavities are reported, where site-controlled quantum dots are positioned at the antinode of the optical mode field in a self-aligned manner without the need of any further nano-processing. It is shown that the cavity properties such as Q-factor, mode volume, and mode splitting can be tailored by the geometry of the integrated buried stressor, with an opening <4 mu m. The experimental results are complemented with theory calculations based on continuum elasticity. Lasing signatures, including super-linear input-output response and linewidth narrowing, are observed for a 3.6-mu m self-aligned cavity with a Q-factor of 18 000. Furthermore, the quasi-planar site-controlled cavities exhibit no detrimental thermal effects. This approach integrates seamlessly with the industrial-matured manufacturing process and the buried-stressor technique, paving the way for exceptional scalability and straightforward manufacturing of high-beta microlasers and bright quantum light sources.