Multiband Hot Photoluminescence from Nanocavity-Embedded Silicon Nanowire Arrays with Tunable Wavelength

Visible upconversion luminescence of doped bulk silicon for a multimodal wafer metrology

We report the experimental observation of the UV-visible upconverted luminescence of bulk silicon under pulsed infrared excitation. We demonstrate that non-stationary distribution of excited carriers leads to the emission at spectral bands never to our knowledge observed before. We show that the doping type and concentration alter the shape of luminescence spectra. Silicon nanoparticles have a size between quantum-confined and Mie-type limits (10-100 nm) yet show increased luminescence intensity when placed atop a silicon wafer. The findings demonstrate that upconversion luminescence can become a powerful tool for nearest future silicon wafer inspection systems as a multimodal technique of measuring the several parameters of the wafer simultaneously.

Three-dimensional cavity-coupled metamaterials for plasmonic color and real-time colorimetric biosensors

Plasmonic structure color has significant potential for visual biochemical sensing by simple instrumentation or even naked eye detection. Herein, we present a visual and real-time sensing strategy for refraction index sensing and detection of the biotin-avidin system based on three-dimensional cavity-coupled metamaterials. These metamaterials composed of a top array of gold disks, aluminium pillars and a bottom reflection film of aluminium have structures similar to the metal-insulator-metal structure. The insulating layer comprises air-gap cavities that are easily filled with gaseous or liquid dielectrics. Therefore, analytes can permeate into the nano-scale cavities and produce strong light-matter interactions. The sensor shows that any tiny change in the refraction index will induce a significant color variation and the sensitivity reaches 683.5 nm per refraction index unit with a figure of merit of 3.5. The color of the metamaterials changes from rose-red to violet and then loden after a monomolecular layer of thiolated biotin and streptavidin bind to the surface of the nanostructure successively. This sensing strategy offers new opportunities for the convenient detection of proteins, nucleic acids, and lipids.

Tuning Electroluminescence from a Plasmonic Cavity-Coupled Silicon Light Source

The combination of Moore's law and Dennard's scaling rules have constituted the fundamental guidelines for the silicon-based semiconductor industry for decades. Furthermore, the enormous growth of global data volume has pushed the demand for complex and densely packed devices. In recent years, it has become clear that wired interconnects impose increasingly severe speed and power limitations onto integrated circuits as scaling slows toward a halt. To overcome these limitations, there is a clear need for optical data processing. Despite significant progress in the development of silicon photonics, light sources remain challenging owing to the indirect bandgap of group IV materials. It is therefore highly desirable to develop new concepts for a silicon light source that meets efficiency and footprint requirements similar to their electronic counterparts. Here, we demonstrate an electrically driven and tunable silicon light source by matching the resonant modes of a silver nanocavity with the hot luminescence spectrum of an avalanching p-n junction. The cavity significantly enhances phonon-assisted recombination of hot carriers by tailoring the local density of states at the size-tunable resonance. Such tunable nanoscale emitter may be of great interest for short-reach communications, microdisplays or lab-on-chip applications.

Improved device performances based on Si quantum dot/Si nanowire hetero-structures by inserting an Al2O3 thin layer

Si quantum dot-based light emitting devices were fabricated on Si nanowire arrays in order to improve light extraction efficiency. However, the device performance is deteriorated by using Si nanowires with a depth of 1.2 μm due to serious surface recombination. By introducing an Al₂O₃ thin layer between the Si quantum dots and Si nanowires, significantly enhanced electroluminescence (∼8.5 fold) has been demonstrated. Based on electron spin resonance, capacitance-voltage and conductance-voltage measurements, the effect of the Al₂O₃ thin layer on the improvement of device performance is quantitatively evaluated. Our results demonstrate that besides the chemical passivation to reduce the surface defect states of Si nanowires, the Al₂O₃ thin layer can act as a barrier layer to confine the injected carriers in the active Si quantum dot layer due to the existence of negatively fixed charges and a potential barrier. As a consequence, radiative recombination is promoted which contributes to the enhanced light emission from devices based on Si quantum dot/Si nanowire hetero-structures.