UC Merced

Solid-state quantum dot molecules (QDMs), systems of two or more coupled quantum dots (QDs), present promising opportunities for creating devices useful for advanced sensing, metrology, communication, and computing operations. In this work, these systems are formed from layered deposition of strained III-V materials that produce spatially aligned nanocrystals capable of charge confinement and susceptible to interdot electron and hole tunneling. When grown in electric field effect structures, the optically generated excitons hosted by these dots are subject to a Quantum Confined Stark Effect (QCSE) which allows for precise and controllable tuning of their energy states and hence their photoluminescence (PL) emissions. These optical transitions are highly sensitive to small fluctuations in the local electronic environment, making them well suited for use in \textit{in situ} nano-scale monitoring.

This dissertation reports on the use of QDMs to directly investigate and monitor the physics of interacting quantum states at the single-charge level. In particular, we develop a model that uses intra and interdot excitonic states to precisely characterize the energy splittings induced by remote charges. We make use of low-temperature optical photoluminescence spectroscopy to explore and measure interacting QDM states and document direct interactions between excitonic states and neighboring defect sites and QDMs. We further show how these can be used to locate and monitor remote charges in bulk semiconducting material, with detection ranges $>35\mu$m.

Additionally, we develop a model that describes the interactions between neighboring QDM excitonic dipoles, and demonstrate that this interaction gives rise to an engineered state that has reduced sensitivity to remote charge induced fluctuations. Samples with lateral and vertical configurations of QDM molecules are studied, and several promising candidates are identified. This will serve to spur the development of useful quantum devices by allowing for engineering schemes that reduce quantum state sensitivity to charge noise.