88 research outputs found
Probing energy barriers and quantum confined states of buried semiconductor heterostructures with ballistic carrier injection: An experimental study
A three-terminal spectroscopy that probes both subsurface energy barriers and
interband optical transitions in a semiconductor heterostructure is
demonstrated. A metal-base transistor with a unipolar p-type semiconductor
collector embedding InAs/GaAs quantum dots (QDs) is studied. Using
minority/majority carrier injection, ballistic electron emission spectroscopy
and its related hot-carrier scattering spectroscopy measures barrier heights of
a buried AlxGa1-xAs layer in conduction band and valence band respectively, the
band gap of Al0.4Ga0.6As is therefore determined as 2.037 +/- 0.009 eV at 9 K.
Under forward collector bias, interband electroluminescence is induced by the
injection of minority carriers with sub-bandgap kinetic energies. Three
emission peaks from InAs QDs, InAs wetting layer, and GaAs are observed in
concert with minority carrier injection.Comment: 11 pages, 4 figures, submitted to Physical Review
Tuning Multipolar Mie Scattering of Particles on a Dielectric-Covered Mirror
Optically resonant particles are key building blocks of many nanophotonic
devices such as optical antennas and metasurfaces. Because the functionalities
of such devices are largely determined by the optical properties of individual
resonators, extending the attainable responses from a given particle is highly
desirable. Practically, this is usually achieved by introducing an asymmetric
dielectric environment. However, commonly used simple substrates have limited
influences on the optical properties of the particles atop. Here, we show that
the multipolar scattering of silicon microspheres can be effectively modified
by placing the particles on a dielectric-covered mirror, which tunes the
coupling between the Mie resonances of microspheres and the standing waves and
waveguide modes in the dielectric spacer. This tunability allows selective
excitation, enhancement, and suppression of the multipolar resonances and
enables scattering at extended wavelengths, providing new opportunities in
controlling light-matter interactions for various applications. We further
demonstrate with experiments the detection of molecular fingerprints by
single-particle mid-infrared spectroscopy, and, with simulations strong optical
repulsive forces that could elevate the particles from a substrate.Comment: 16 pages, 4 figure
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