Heterogeneous integration of III–V materials with silicon-on-insulator (SOI) waveguide circuitry by an adhesive die-to-wafer bonding process has been proposed as a solution to Si-based lasers and photodetectors. Here, we present the design and optimization of an InGaAs PIN photodetector vertically coupled with the underlying SOI waveguide, which could be readily fabricated using this bonding process. With the help of grating couplers, a thick bonding layer of 2.5 μm is applied, which inherently avoids the risk of low-bonding yield suffering in the evanescent coupling counterpart. An anti-reflection layer is also introduced between the bonding layer and the III–V layer stack to relieve the accuracy requirement for the bonding layer thickness. Besides, by optimizing the structure parameters, a high-absorption efficiency of 82% and a wide optical 1dB-bandwidth of 220nm are obtained. The analysis shows that the detection bandwidth of the present surface-illuminated photodetector is generally limited by transit-time in the i-InGaAs layer. The relationship of the detection bandwidth and the absorption efficiency versus the i-InGaAs layer thickness is presented for the ease of choosing proper structure parameters for specific applications. With the results presented here, the device can be readily fabricated.
We report a polarization-dependent reflector beyond normal incidence with a subwavelength nanoparticle chain. Polarization-dependent reflection with high reflectivity or high transmissivity can be obtained with this structure. Light waves of transverse electric/magnetic mode will be reflected, while the transverse magnetic/electric mode will transmit through. The structure shows a certain degree of tolerance of incident angle, technical fabrication, and even particle shape. We hope the low-loss and compact structure can find applications in photonic circuits such as gallium nitride-based light sources.
Grating couplers are widely investigated as a coupling interface between silicon-on-insulator waveguides and optical
fibers. In this work, novel grating couplers based on strip poly-Si are proposed. This structure utilizes the poly-Si gate
layer of the CMOS MOSFETs, and thus enables grating couplers integrated with CMOS circuits without adding any
additional masks and process steps. Simulation results show that a coupling efficiency over 60% can be achieved
between silicon-on-insulator waveguides and fibers.
Fabrication and characterization of an integrated 3-D linear taper are reported, which is based on (111) silicon-on-insulator for efficient coupling between a single-mode fiber and planar photonic devices. The fabrication process involved wafer bonding, anisotropic etching, and dry etching. The 3-D taper measured 75 µm in length. The input waveguide, 5.6×5 µm2 in dimensions of the end facet, was compressed to dimensions of 0.6×1.8 µm2 of the end facet in the output waveguide. The measured average net transmission loss was 0.52 dB at the wavelength of 1.55 µm.
A numerical calculation of coupling efficiency of planar metal grating coupled GaAs/AlGaAs quantum well infrared detectors has been made in this work. The results showed that the coupling efficiency is a function of the ratio of the grating period (Lambda) to the intersubband resonance wavelength (lambda) for various degrees of metal filling. In the vicinity of n(Lambda) /(lambda) < 1 (n is the refractive index), filling factors round 0.5 - 0.7 give large longitudinal electric-field components, which induces a strong coupling to the intersubband absorption in the quantum well structures of the semiconductor. Numerical calculations provide detailed guidelines for obtaining optimum coupling for GaAs/AlGaAs quantum well infrared detectors.
In this paper a new, modified s-d model for studying the quantum well states in a metal space of a magnetic metal sandwich structure is presented. The model is based on the following consideration that (1) in the direction perpendicular to the surface the conduction electron is limited in an infinite deep potential well; (2) the localized magnetic moment model is adapted for describing the atoms in the ferromagnetic layers; (3) the spin-flip scattering process is neglected because of the Heisenburg interaction. The resulted electron states are that the energy level is split into two symmetrical ones for a ferromagnetic configuration, which is in agreement with the recent experiments on the exchange-split spin- polarized electronic states. It is found that this simple model can explain the oscillatory exchange coupling with long period well.
The anomalous damage behavior of BF2+ implantation into silicon at 300 K and 77 K has been investigated by using grazing angle Rutherford backscattering and channeling in combined with transmission electron microscopy. The damage or the amorphous layer produced by BF2+ implantation is different from other heavier ions (> 27Al+). For BF2+ implantation at 300 K, there are two damage peaks, one at a depth near the projectile range of the ions, the other at the near surface. While for BF2+ implantation at 77 K, the damage or the amorphous layer first occurs at the surface, then the amorphous layer is extended to the bulk of silicon with increasing does.
The main research activities of thin film synthesis by ion beam technique in Shanghai Institute of Metallurgy (SIM) are reviewed. Hard and metal alloy coatings, such as TiN, TiBx, SiNx, DLC (diamond like carbon), Pt, and NI/Cr-Ag, are synthesized by ion beam assisted deposition (IBAD) on different kinds of substrates at room temperature. The mechanical, electrical properties and the microstructure of the films were systematically analyzed and discussed with the formation conditions. The experimental result reveals that one of the outstanding characteristic of the IBAD films is the very strong adhesion strength to the substrates. Buried layer formation by ion implantation is one of another newly developed technique. The formation of buried insulating layer in silicon crystal is carried out by high dose O+ and N+ implantation. Epitaxial growth of high Tc YBCO superconductive thin films on SrTiO3 is studied by DC magnetron sputtering.
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