silicon and lead-selenide

We report coupling of the excitonic photon emission from photoexcited PbSe colloidal quantum dots (QDs) into an optical circuit that was fabricated in a silicon-on-insulator wafer using a CMOS-compatible process. The coupling between excitons and sub-μm sized silicon channel waveguides was mediated by a photonic crystal microcavity. The intensity of the coupled light saturates rapidly with the optical excitation power. The saturation behaviour was quantitatively studied using an isolated photonic crystal cavity with PbSe QDs site-selectively located at the cavity mode antinode position. Saturation occurs when a few μW of continuous wave HeNe pump power excites the QDs with a Gaussian spot size of 2 μm. By comparing the results with a master equation analysis that rigorously accounts for the complex dielectric environment of the QD excitons, the saturation is attributed to ground state depletion due to a non-radiative exciton decay channel with a trap state lifetime ~ 3 μs.

Topics: Colloids; Electrochemistry; Electromagnetic Radiation; Equipment Design; Helium; Lead; Materials Testing; Microscopy, Electron, Scanning; Models, Statistical; Neon; Normal Distribution; Photons; Quantum Dots; Selenium Compounds; Silicon; Solvents

Semiconductor nanocrystals are called artificial atoms because of their atom-like discrete electronic structure resulting from quantum confinement. Artificial atoms can also be assembled into artificial molecules or solids, thus, extending the toolbox for material design. We address the interaction of artificial atoms with bulk semiconductor surfaces. These interfaces are model systems for understanding the coupling between localized and delocalized electronic structures. In many perceived applications, such as nanoelectronics, optoelectronics, and solar energy conversion, interfacing semiconductor nanocrystals to bulk materials is a key ingredient. Here, we apply the well established theories of chemisorption and interfacial electron transfer as conceptual frameworks for understanding the adsorption of semiconductor nanocrystals on surfaces, paying particular attention to instances when the nonadiabatic Marcus picture breaks down. We illustrate these issues using recent examples from our laboratory.

Topics: Adsorption; Chemistry, Physical; Electronics; Lead; Microscopy, Electron, Scanning; Models, Chemical; Quantum Dots; Selenium Compounds; Semiconductors; Silicon; Surface Properties; Titanium

Coherent and directional emission at 1.55 μm from a PbSe colloidal quantum dot electroluminescent device on silicon is demonstrated. The quantum dots are sandwiched between a metallic mirror and a distributed Bragg reflector and are chemically treated in order to increase the electronic coupling. Electrons and holes are injected through ZnO nanocrystals and indium tin oxide, respectively. The measured electroluminescence exhibits a minimum linewidth of ~3.1 nm corresponding to a cavity quality factor of ~500 at a low injection current density of 3 A/cm2, and highly directional emission characteristics.

Topics: Colloids; Lead; Luminescent Measurements; Optical Devices; Quantum Dots; Refractometry; Selenium Compounds; Silicon