Compared to the highly sensitive silicon based affordable visible light detectors, infrared photodetectors require significant improvement. Localized surface plasmon resonances of metal nanoparticles can be utilized for increasing the absorption efficiency of semiconductors suited for detection of infrared radiation. In this work, plasmonic gold nanorods (AuNRs) are used to enhance generation of charge carriers and photon emission by InAs/InGaAs/GaAs quantum dots-in-a-well semiconductor heterostructures. Comparison of measured and calculated scattering spectra reveals that the AuNRs on GaAs exhibit red to green colors depending on their proximity to the GaAs surface. On the other hand, theoretical and experimental near-field optical characterization show that the electric field is tightly localized at the AuNR-GaAs interfacial regions, creating a convenient platform for investigating localized carrier generation and diffusion by monitoring the emission of InAs QDs. The carrier generation and photon emission enhancement is studied as a function of the GaAs thickness (distance) and temperature. Analysis of the QD emission enhancement as a function of distance reveals a Förster radius of 3.85 ± 0.15 nm, a near-field decay length of 4.8 ± 0.1 nm and an effective carrier diffusion length of 64.0 ± 3.0 nm. These distance parameters indicate two emission enhancement mechanisms: plasmon enhanced carrier generation inside the GaAs layer and diffusion to the InAs QDs, and direct near-field excitation of the InAs/InGaAs quantum well. The emission enhancement increases with temperature, confirming the importance of charge carrier diffusion from the GaAs to the InAs QDs, where recombination and photon emission takes place.
We propose a facile approach to fabricate graphene nano-objects (GNOs) using interference lithography (IL) and direct
self-assembly of nanoparticles. Uniformly spaced parallel photoresist (PR) lines and periodic hole arrays are proposed as
an etch mask for producing graphene nanoribbons (GNRs), and graphene nanomesh (GNM), respectively. In a different
experiment, the PR line arrays are transferred to uniform oxide channels, and silica nanoparticle dispersions with an
average size of 10 nm are spun on the patterned surface, leaving a monolayer uniform nanoparticle assembly on the
graphene. Following the particle deposition, the graphene is removed in the narrow spacing between the particles, using
the O2 plasma etch, leaving ordered graphene quantum dot (GQD) arrays. The IL technique and etch process enables
tuning the GNOs dimensions.