High-Responsivity Photodetector in Standard SiGe BiCMOS Technology

For high-speed optoelectronic applications such as fiber-optic data communication systems, photodetectors (PDs) with high responsivity in Si-related processes are required. In this letter, a result of the effort along this line is reported. A novel device named phototransistor PD (PTPD) was realized in a commercial 0.35-mum SiGe BiCMOS technology. The device combines a surface PD (SPD) and a conventional SiGe heterojunction PT (HPT). It was shown that the SPD enhanced light absorption and the PTPD showed significant performance improvement over HPT. Responsivities of 5.2 A/W for an 850-nm light and 9.5 A/W for a 670-nm light were achieved in the PTPD, with floating base and SPD terminals.     

A wavelet transform based POCS Superresolution algorithm

Research interest in multi-frame Superresolution has risen substantially in recent years.This paper presents a modified Projection Onto Convex Set (POCS) superresolution method based on wavelet transform.The method analyzes the image formation model from wavelet multiresolution analysis point of view and defines an closed convex set and its corresponding projection based on wavelet transform.An iterative procedure is utilized to reduce the estimated errors of the result image,and this guarantees the estimated image to lay in the intersection of different convex sets,thus produces a high resolution image with a reduced error.The effectiveness of the algorithm is demonstrated by experimental results.     

Kaluza-Klein black hole in a six-dimensional Poincaré gauge theory of gravitation

We found a solution to the six-dimensional Poincaré gauge theory which can be interpreted as the exterior gravitational field of an uncharged black hole in the four-dimensional spacetime. The extra dimensions are curled up into a compact space of the size characterized by the Planck length.     

A 1.9 Gb/s 358 mW 16–256 State Reconfigurable Viterbi Accelerator in 90 nm CMOS

A 16-256 state coarse-grain reconfigurable Viterbi accelerator fabricated in 1.3 V_t 90 nm dual-CMOS technology is described for 3.8 GHz operation, with 1.9 Gb/s data rate in 32-state mode. Radix-4 ripple-carry ACS circuits, reconfigurable path metric read/write control, and tree-bitline traceback memory circuits with programmable ring-buffer decoders enable 358 mW total power, measured at 1.3 V, 50degC, with performance scalable to 2.35 Gb/s at 1.7 V, 50degC.     

Laser thermal processing of amorphous silicon gates to reduce poly-depletion in CMOS devices

One major challenge in advanced CMOS technology is to have adequate dopant activation at the polycrystalline silicon (poly-Si) gate/gate oxide interface to minimize the poly-Si depletion effect. In this paper, laser thermal processing (LTP) was employed to fabricate single or dual-layer poly-Si-gated MOS capacitors with ultrathin gate oxides. Capacitance-voltage data show that the carrier concentration at the poly-Si gate/gate oxide interface increases substantially when the devices are subjected to LTP prior to a rapid thermal anneal (RTA). Thus, LTP readily reduces the poly-depletion thickness in MOS devices. For p/sup +/-gated capacitors, this is achieved with boron penetration that is equivalent to the control sample with 1000/spl deg/C, 5 s RTA (without LTP). In addition, results from secondary ion mass spectrometry indicate that the concentration of dopants near the critical gate/gate oxide interface increases significantly after a post-LTP anneal, in good agreement with the electrical data. Time-dependent dielectric breakdown studies show that the gate oxide reliability is not degraded even after LTP at high fluences.     

Synthesis and characterization of new light‐emitting copolymers in polymeric‐light‐emitting‐diode device fabrications

A series of thiophene‐containing photoactive copolymers consisting of alternating conjugated and nonconjugated segments were synthesized. The ¹H NMR spectra corroborated the well‐defined structures, and the copolymers not only were soluble in common organic solvents but also had high glass‐transition temperatures (ca. 130 °C) and good thermal stability up to 390 °C. Introducing aliphatic functional groups, such as alkyl or alkoxyl, into chromophores of the copolymers redshifted the photoluminescence spectra and lowered the optical bandgaps. The electrochemical bandgaps calculated from cyclic voltammetry agreed with the optical bandgaps and thus indicated that electroluminescence and photoluminescence originated from the same excited state. The energy levels (highest occupied molecular orbital and lowest unoccupied molecular orbital) of all the copolymers were lower than those of poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1.4‐phenylenevinylene] MEH–PPV, indicating balanced hole and electron injection, which led to improved performance in both single‐layer and double‐layer polymeric‐light‐emitting‐diode devices fabricated with these copolymers. All the copolymers emitted bluish‐green or green light above the threshold bias of 5.0 V under ambient conditions. At the maximum bias of 10 V, the electroluminescence of a device made of poly(2‐{4‐[2‐(3‐ethoxy phenyl)ethylene]phenyl}‐5‐{4‐[2‐(3‐ethoxy,4‐1,8‐octanedioxy phenyl)ethylene]phenyl}thiophene) was 5836 cd/m². The external electroluminescence efficiency decreased with the lifetime as the polymer degraded. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3954–3966, 2004     

Kaluza-Klein unification in the poincaré gauge theory of gravitation

We show that we can unify the gravitational and internal gauge interactions in a high dimensional Riemann-Cartan spacetime in the spirit of Kaluza-Klein, if we identify some of the connection coefficients as Yang-Mills potentials and if the dynamics of the spacetime is governed by the Poincaré gauge theory of gravitation whose lagrangian contains curvature and torsion squared.     

The phenylcarbene rearrangement revisited

The evolution of mechanistic ideas about the phenylcarbene rearrangement has been reviewed, and three closely linked problems have been identified toward whose solution this research has been aimed: 1. Why do the ratios of the stable end products from the rearrangements of o-, m- and p-tolylmethylene differ when all three reactions have been throught to pass through a common intermediate? 2. Why does the rearrangement of 2-methylcycloheptatrienylidene lead to exclusive formation of styrene? 3. What is the mechanism of styrene formation from o-tolylmethylene? New mechanisms have been proposed in which m- and p-tolylmethylene can rearrange to styrene without necessarily being converted to o-tolylmethylene. The formation of a small amount of 2,6-dimethylstyrene from the rearrangement of 3,4,5-trimethylphenylmethylene is viewed as evidence for such a mechanism, and a set of interconverting norcaradienylidenes are believed to be the crucial intermediates. Other alternatives are considered and rejected on the basis of the rearrangement products of 3,5-dimethyl- and 3,4,5-trimethylphenylmethylene.     

Thin polyoxide on the top of poly-Si gate to suppress boronpenetration for pMOS

A method of using a thin oxide on the top of the poly-Si gate to getter fluorine for BF₂⁺ in pMOS is proposed and demonstrated. Due to less amount of fluorine in the poly-Si as well as in the gate oxide, the boron penetration through the gate oxide is suppressed. The MOS capacitors fabricated by using this method show less shifts and distortion on C-V curves and better electrical characteristics