A symmetrically stacked structure [(a-Si:H(n+)/a-Si:H(i)/CZ wafer (n)/a-Si:H(i)/a-Si:H(n+)] was used to optimize the growth process conditions of the n-type hydrogenated amorphous silicon [a-Si:H(n+)] thin films. Here a-Si:H(n+) film was used as back surface field (BSF) layer for the silicon heterojunction solar cell and all stacked films were prepared by conventional radio-frequency plasma-enhanced chemical vapor deposition. The characterizations of the effective carrier lifetime (τeff), electrical and structural properties, as well as correlation with the hydrogen dilution ratio (R=H2/SiH4) were systematically discussed with the emphasis on the effectiveness of the passivation layer using the lifetime tester, spectroscopic ellipsometry, and hall measurement. High quality of a stacked BSF layer (intrinsic/n-type a-Si:H layer) with effective carrier lifetime of 1.8 ms can be consistently obtained. This improved passivation layer can be primarily attributed to the synergy of chemical and field effect to significantly reduce the surface recombination.
In this Letter, the identification device disclosed in the present invention is comprised of: a carrier
and a plurality of pseudo-pixels; wherein each of the plural pseudo-pixels is formed on the carrier
and is further comprised of at least a light grating composed of a plurality of light grids. In a
preferred aspect, each of the plural light grids is formed on the carrier while spacing from each
other by an interval ranged between 50nm and 900nm. As the aforesaid identification device can
present specific colors and patterns while it is being viewed by naked eye with respect to a
specific viewing angle, the identification device is preferred for security and anti-counterfeit
applications since the specific colors and patterns will become invisible when it is viewed while
deviating from the specific viewing angle.
Coupling of a InGaN/GaN multi-quantum well (MQW) and semitransparent metal layer is shown to result in dramatic
enhancement of spontaneous emission rate by the surface plasmon effect in the optical spectral range. A five-pairs
18.5nm InGaN/GaN MQW is positioned 175nm, form various thickness (t=5~50nm) silver layer. And periodic patterns
(p=0.25~0.8μm) are defined in the top semitransparent metal layer by e-beam lithography, which are grating structures
can be incorporated into the metal film to excite surface plasmon between the interference of the metal film and
semiconductor. We have experimentally measured photoluminescence intensity and peak position of spontaneous
emission of the fabricated structures and compared with the unprocessed samples, whilst still ensuring that most of the
emission takes place into the surface plasmon (SP) mode. And the implication of these results for extracting light by
reducing total internal reflection (TIR) from light emission diode is discussed.
We develop a miniaturized optical signal pickup module, with a working wavelength of 650 nm, and an image numerical aperture (NA) of 0.6, comprised of several SiNX optical phase elements on stacked Si substrates, for use in optical storage systems. The optical module, which is optical-on-axis and transmissible in both visible and infrared ranges, is designed to include not only a light source, but also diffractive optical elements (DOEs), which can be made with micro-optoelectromechanical systems (MOEMS) technology. Its optical operation is simulated by ray tracing to optimize the spot size (~0.6 µm) focused on the disk by adjusting the tolerance of each element in the alignment. All the Si-based transmission optical elements are fabricated and stacked by self-alignment bonding to reduce the tolerance of the assembled system. We obtain a circular focused spot when the full-width at half maximum (FWHM) of the zero-order beam is 3.1 µm; the diffraction limited spot size on the optical disk is 0.7 µm.
In this paper, fabrication an optical filter based on guided-mode resonance (GMR) effect in a silicon nitride (SiNx) membrane by silicon bulk micromachining technologies is demonstrated. Such a filter has advantages of simple structure, high efficiency and it is potential to be integrated with other developed optoelectronic elements into an integrated micro systems. The design consideration, fabrication procedures and measured spectral response are shown in this paper.
The hydrogenated Silicon nitride film is well developed to form a passivation layer for non-volatile memory devices. It has many superior chemical, electrical, and mechanical properties. In addition, it also has excellent optical properties. It is transparent in UV and DUV range, with a high refractive index of about 1.7~2. Owing to its superior mechanical and optical properties, we used a hydrogenated silicon nitride (SiNXHY) membrane as an optical phase element. By using e-beam lithography, we demonstrate on feasibility for the fabrication of subwavelength optical elements, such as waveplate, polarizer, and polarized beam splitter on a silicon-based low stress SiNXHY membrane for the UV region applications. An SiNXHY film was deposited by plasma enhanced chemical vapor deposition (PECVD) and the free- standing membrane is formed by KOH silicon backside etching, from which substrate materials are removed. The membrane's morphology and geometries of subwavelength optical elements were verified by means of an scanning electron microscope (SEM), and the optical performance characteristics of these subwavelength optical elements are shown. The experimental datas agree well with theoretical predictions.
The optical transmission and distribution through a subwavelength slit on a tapered metallic substrate was investigated. By using a 45° tapered structure, 6 times larger transmission enhancement was achieved compared with a traditional metallic plate structure because of the asymmetric excited surface waves and the matching of propagation constants between the surface waves and slit waveguide. In addition, a focus beam was obtained by patterning surface corrugations in the exit plane. By tuning the period of the surface corrugations, we were able to adjust the focal length with a spot size smaller than the diffraction limit. The focal point can be kept about 0.6μm with a focal length from 0.5μm to 2.5μm for a grating period from 0.5μm to 0.6μm.
Homoepitaxial and heteroepitaxial ZnO films were grown by plasma-assisted molecular beam epitaxy (P-MBE). Homoepitaxial ZnO layers were grown on an O-face melt-grown ZnO (0001) substrate. Heteroepitaxial ZnO layers were grown on an epitaxial GaN template predeposited by metalorganic chemical vapor deposition on a c-plane sapphire substrate. There exists a residual strain in the heteroepitaxial ZnO, which is ε = -0.25%. Low-intensity excitation PL spectra of ZnO epilayers excited by a He-Cd laser exhibit only bound-exciton emission with phonon replicas. The quality of ZnO epilayers is better than that of ZnO substrate. However, under high-intensity excitation by a N2 laser, the emission due to exciton-exciton collisions dominates the PL spectrum from heteroepitaxial ZnO layer but is not observed from homoepitaxial ZnO layer.
We have proposed a miniaturized optical signal pickup module comprised of several SiNX membrane devices on stacked Si substrates for use in optical storage system. The optical module was designed to include not only light sources and detectors, but also the diffractive optical elements (DOEs), which can be made with microoptoelectromechanical systems (MOEMS) technology. Its optical operation was simulated by ray-tracing to have an optimized spot size (~0.6μm) focused on the disk with setting the tolerance of each element for the alignment. All these Si-based transmission optical elements were fabricated and can be stacked by self-alignment bonding for system assembly.
We have developed a novel stacked silicon-based microoptical system, which is optical-on-axis and transmissible in both visible and infrared ranges. By using the new microoptical system techniques, we fabricated a miniaturized optical pickup head module. This optical pickup head consisted of a 650nm laser diode, a 45 degrees silicon reflector, a grating, a holographic optical element, and some aspherical Fresnel lenses. These optical phase elements fabricated on a SiNx membrane were free-standing on Si chips. Each element was then stacked by chip bonding. We could obtain a circular focusing spot on the optical disc as small as 3.1um.
An out-of-plane guided-mode resonance (GMR) filter on a single Si chip using a two-layer polysilicon surface micromachining process was proposed. To the best of our knowledge, this is the first time that a monolithic optical filter has been integrated on a silicon microoptical bench. This device can be used as a bi-directional transceiver filter. The extinction ratio between 1550nm and 1310nm could be as low as 40dB and the channel passband at 1550nm was 20nm.
Silicon nitride (SiNX) film is a commonly used material in silicon technology. In addition, it has excellent optical properties. It is transparent in both the UV and visible range, with a high refractive index of about 1.7~2. Owing to its superior mechanical and optical properties, we used a silicon nitride membrane as an optical phase element. We will fabricate nano-structured diffractive optical elements, such as wave-plate, polarizer, and polarized beam splitter on SiNXHY membrane by e-beam lithography for the UV-visible regime applications. The SiNXHY membranes were made from SiNXHY films deposited by an plasma enhanced chemical vapor deposition (PECVD) as an alternative method for low stress membrane fabrication used in UV-visible transmittance. The stress of silicon nitride film showed a change from compressive to tensile with increasing working pressure during film deposition. The UV-visible transmittance of the free standing membrane was measured, which showed that UV light is transparent at wavelength as short as 240nm. We will show the feasibility to fabricate nano-structured diffractive optical elements on the SiNXHY membrane combined with microoptoelectromechanical systems (MOEMS) technology for the application in the UV-visible regimes.
Optical elements, such as grating, holographic optical element and Fresnel lens, are made on the SiN membrane. The SiN film was deposited on the silicon wafer by low pressure chemical vapor deposition (LPCVD). Its advantages include the high transmission efficiency, light weight, and easy packaging for the Si-based optical pickup head.