Silicon Photonics taps on the volume manufacturing capability of traditional silicon manufacturing techniques, to
provide dramatic cost reduction for various application domains employing optical communications technology. In
addition, an important new application domain would be the implementation of high bandwidth optical interconnects in
and around CPUs. Besides volume manufacturability, Silicon Photonics also allows the monolithic integration of
multiple optical components on the same wafer to realize highly compact photonic integrated circuits (PICs), in which
functional complexity can be increased for little additional cost. An important pre-requisite for Si PICs is a device library
in which the devices are compatibly developed around a common SOI platform. A device library comprising passive and
active components was built, which includes light guiding components, wavelength-division-multiplexing (WDM)
components, switches, carrier-based Si modulators and electro-absorption based Ge/Si modulators, Ge/Si photodiodes
and avalanche photodiodes, as well as light emitting devices. By integrating various library devices, PIC test vehicles
such as monolithic PON transceivers and DWDM receivers have been demonstrated. A challenge with Si PICs lies with
the coupling of light into and out of the sub-micrometer Si waveguides. The mode size mismatch of optical fibers and Si
waveguides was addressed by developing a monolithically integrated multi-stage mode converter which offers low loss
together with relaxed fiber-to-waveguide alignment tolerances. An active assembly platform using MEMS technology
was also developed to actively align and focus light from bonded lasers into waveguides.
An efficient low-voltage lateral current-injection CMOS-compatible light emitting diode (LED) based on Si/SiO2
multiple quantum wells (MQW) is reported. This is the first time that a lateral current-injection LED is demonstrated
with Si/SiO2 MQW structures. Strong electroluminescence (EL) in the wavelength ranging from 450 to 850 nm can be
observed when the device is reverse-biased at the voltage of as low as ~6 V with the current of ~1 mA. With the lateral
current injection structure, the working voltage of the LED is significantly reduced because the voltage is fully applied
across the active region instead of dielectrics which cannot be avoided in vertical current-injection Si/SiO2 quantum well
LEDs that have received intensive research attention during the last decade. The external quantum efficiency is ~20
times higher than that of the conventional vertical current-injection LEDs based on Si/SiO2 MQW. The light emission
would probably originate from the impact ionization due to the hot carriers generated in ultra-thin Si film when the
device is reverse-biased. The lateral configuration provides a versatile technology platform, since many light-extraction
and mono-chromaticity enhancement techniques can be directly applied onto the top emission window.
Because of the its indirect bandgap structure, it is a huge challenge to establish an efficient Si light emitting diode (LED) compatible with complementary metal-oxide-semiconductor (CMOS) process. In this paper, we provide an alternative
route to overcome this difficulty based on the unique property of photonic crystals (PhC). A vertical-current-injection
LED based on three-dimensional-confined structures with triangular-lattice air-hole PhC patterns has been fabricated
with enhanced light extraction from the active region (i.e., silicon-rich-oxide/SiO2 multilayer stack). The intensity and
profile of photoluminescence (PL) and electroluminescence (EL) has been found to be efficiently modulated by
controlling the optical modes of the periodic arrays via varying their structural parameters. It provides a convenient way
of redistributing the light energy in desired form and orientation. With optimized lattice constant/radius ratio, significant
enhancement up to ~7 times in both PL and EL emissions can be obtained. The mechanisms for different enhancement
features have also been theoretically analyzed based on coherent scattering and quantum electrodynamics effects, which
is well consistent with the experiment observation.
Both isolated Si nanocrystals (nc-Si) dispersedly distributed in a SiO2 matrix and densely stacked nc-Si layers embedded
in SiO2 have been synthesized with the ion implantation technique followed by high temperature annealing. The
dielectric functions of the isolated nc-Si and densely-stacked nc-Si layer embedded in SiO2 have been determined with
spectroscopic ellipsometry (SE) in the photon energy range of 1.1-5 eV. The dielectric functions of these two different Si
nanostructures were successfully extracted from the SE fitting based on a multi-layer fitting model that takes into
account the distribution of nc-Si in SiO2 and a five phase model (i.e., air/SiO2 layer/densely-stacked nc-Si layer/SiO2
layer/Si), respectively. The dielectric spectra of isolated nc-Si distributed in SiO2 present a two-peak structure, while the
dielectric spectra of densely-stacked nc-Si layer show a single broad peak, being similar to that of amorphous Si. The
dielectric functions of these two Si nanostructures both show significant suppressions as compared with bulk crystalline
Si. However, it has been observed that the densely stacked nc-Si layer exhibits a more significant suppression in the
dielectric spectra than the isolated nc-Si dispersedly embedded in SiO2. This is probably related to the two factors: (i) the
nc-Si size (~3 nm) of the densely stacked nc-Si layer is smaller than that (~4.5 nm) of the isolated nc-Si embedded in
SiO2 matrix, and (ii) the densely stacked nc-Si layer has an amorphous phase.
Light emitting diodes (LEDs) based on a metal-oxide-semiconductor-like (MOS-like) structure with Si nanocrystals (nc-Si) embedded in SiO2 have been fabricated with low-energy ion implantation. Under a negative gate voltage as low as ~-5 V, both visible and infrared (IR) electroluminescence (EL) have been observed at room temperature. The EL spectra
are found to consist of four Gaussian-shaped luminescence bands with their peak wavelengths at ~460, ~600, ~740, and
~1260 nm, in which the ~600-nm band dominants the spectra. The EL properties have been investigated together with
the current transport properties of the Si+-implanted SiO2 films. A systematic study has been carried out on the effect of
the Si ion implantation dose and the energy on both the current transport and EL properties. The mechanisms of the
origin of the four different EL bands have been proposed and discussed.
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