Yuxing Huang

Major: Physics

Mentors: Sean Doan, Galan Moody

Cryogenic Electrical and Optical Control of Site-Controlled III-V Semiconductor Quantum Dots

Quantum communication relies on light sources that can emit streams of single photons. III-V semiconductor quantum dots (QDs) are ideal single-photon sources. However, QDs self-assemble and form at random positions, and in coherent resonance-fluorescence measurements, the excitation laser and emitted photons have the same wavelength eliminating spectral filtering schemes. This interferes with signal detection due to laser scattering. Therefore, this project aims to develop electrical control and coherent optical characterization schemes to study site-controlled quantum dots at cryogenic temperatures. Here, we use strain-induced pre-patternization technology to grow indium gallium arsenide QDs. Thermal-expansion mismatch between different materials creates a nonuniform strain field that guides surface adatoms toward designated positions. This allows for site control of QDs. A custom printed circuit board is designed to provide an electrical interface between the QD device and external electronics. Gate voltages can then be applied to control the QD charge state and stark tune its emission wavelength. Preliminary photoluminescence measurements show emission peaks from neutral excitons, biexcitons, and charged excitons in the site-controlled QDs. A cross-polarized dark-field filtering scheme is planned to be utilized to suppress scattered laser photons during resonance-fluorescence measurements. These measurements will enable further characterization of electrically and optically controlled QDs.