Design consideration and performance of a new MOS imaging device

The design considerations and performance of a new MOS imaging device with novel random noise suppression (RANS) circuits are described. This device consists of 492 × 388 photodiodes, a vertical shift register, and a horizontal BCD register integrated in p-wells. The RANS circuits accelerate the charge-transfer speed from vertical signal lines to a horizontal BCD register with 98-percent efficiency. They also decrease the effective signal line capacitance, so noise due to the transfer MOS switches is suppressed to obtain a high signal-to-noise ratio of 46 dB at a standard scene illumination of 180 lx (F1.4) with no image lag and blooming. Sweep out operation for the smear charge accumulated in the vertical signal lines realizes a sufficient signal-to-smear ratio of 69 dB at 1/10 vertical scene illumination.     

High-speed Ga0.47In0.53As/InP infra-redSchottky-barrier photodiodes

The authors report a new high-speed InP-based Ga_1-xIn _xAs infra-red Schottky-barrier photodiode. The photodiodes were fabricated on both p- and n-GaInAs epilayers using Schottky barrier height enhancement technology. The response speed was measured by the impulse response and autocorrelation method; the risetimes of 85 ps for p-GaInAs and 180 ps for n-GaInAs photodiodes were obtained, which correspond to the 3 dB cutoff frequency of 2-4 GHz. The intrinsic response speed was 12 GHz for n-GaInAs and 18 GHz for p-GaInAs photodiodes based on SPICE simulation with measured device parameters. The photodiodes had the responsivity as high as 0.55 A/W and the quantum efficiency of up to 45% at 1.3-1.6 μm without antireflection coating     

50-nm T-gate metamorphic GaAs HEMTs with f/sub T/ of 440 GHz and noise figure of 0.7 dB at 26 GHz

GaAs-based transistors with the highest f/sub T/ and lowest noise figure reported to date are presented in this letter. A 50-nm T-gate In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As metamorphic high-electron mobility transistors (mHEMTs) on a GaAs substrate show f/sub T/ of 440 GHz, f/sub max/ of 400 GHz, a minimum noise figure of 0.7 dB and an associated gain of 13 dB at 26 GHz, the latter at a drain current of 185 mA/mm and g/sub m/ of 950 mS/mm. In addition, a noise figure of below 1.2 dB with 10.5 dB or higher associated gain at 26 GHz was demonstrated for drain currents in the range 40 to 470 mA/mm at a drain bias of 0.8 V. These devices are ideal for low noise and medium power applications at millimeter-wave frequencies.     

Experimental demonstration of in-loop intracavity intensity-noise suppression

Experimental results for intracavity-laser intensity-noise suppression, or "squashing," manifested as reduced fluctuations on the transmitted field photodetector voltage are presented. It is experimentally demonstrated that a rigid optical cavity within the feedback loop is compatible with squashing. The observed closed loop detector noise floor is approximately 16 nV/sub rms///spl radic/Hz in the acoustic frequency range (/spl sim/100 Hz), well below the quantum limit due to shot noise of 148 nV/sub rms///spl radic/Hz. This corresponds to 19 dB of observed noise suppression below the quantum limit and is consistent with the measured disturbance suppression function of the feedback loop. We also present measurements demonstrating the orthogonality of the squashing and frequency-locking control loops.     

A monolithic, standard CMOS, fully differential optical receiver with an integrated MSM photodetector

This paper presents a realization of a silicon-based standard CMOS, fully differential optoelectronic inte grated receiver based on a metal-semiconductor-metal light detector (MSM photodetector). In the optical receiver, two MSM photodetectors are integrated to convert the incident light signal into a pair of fully differential photo generated currents. The optoelectronic integrated receiver was designed and implemented in a chartered 0.35 μm, 3.3 V standard CMOS process. For 850 nm wavelength, it achieves a 1 GHz 3 dB bandwidth due to the MSM pho todetector's low capacitance and high intrinsic bandwidth. In addition, it has a transimpedance gain of 98.75 dBΩ, and an equivalent input integrated referred noise current of 283 nA from 1 Hz up to -3 dB frequency.     

High performance W-band InAlAs-InGaAs-InP HEMTs

0.15 mu m T-gate lattice-matched In/sub 0.52/Al/sub 0.48/As-In/sub 0.53/Ga/sub 0.47/As-InP HEMTs with a device minimum noise figure of 1.7 dB with 7.7 dB associated gain at 93 GHz have been fabricated. A single-ended active mixer was fabricated using these devices, and a conversion gain of 2.4 dB was measured with 7.3 dB single-sideband noise figure at 94 GHz. This is the first reported active mixer conversion gain at W-band.<>     

Measurement of nonlinear distortion in photodiodes

The 2nd-order nonlinear distortion of avalanche photodiodes (TIXL-55, C-20817) was found to be less than ?60 dB for an incident average optical power of ?20 dBm modulated at a peak depth of 75%. p-i-n photodiodes (HP 5082-4207) were found to have 2nd-order-distortion levels below the noise level. A method using three independent optical signal sources was employed in the measurement.     

Narrow-stripe distributed reflector lasers with first-order vertical grating and distributed Bragg reflectors

Narrow-stripe 1.55-/spl mu/m wavelength distributed reflector lasers consisting of both distributed Bragg reflectors and vertical grating of the first Bragg order were fabricated. A low threshold current I/sub th/ of 2.8 mA, a differential quantum efficiency /spl eta//sub d/ of 28% from the front facet, and a submode suppression ratio of 44 dB were obtained for structures with a stripe width of 1.3 /spl mu/m and a cavity length of 150 /spl mu/m.     

Optimized breakdown probabilities in Al/sub 0.6/Ga/sub 0.4/As-GaAs heterojunction avalanche photodiodes

Recently, it has been shown that the noise characteristics of heterojunction Al/sub 0.6/Ga/sub 0.4/As-GaAs avalanche photodiodes (APDs) can be optimized by proper selection of the width of the Al/sub 0.6/Ga/sub 0.4/As layer. Similar trends have also been shown theoretically for the bandwidth characteristics. The resulting noise reduction and potential bandwidth enhancement have been attributed to the fact that the high bandgap Al/sub 0.6/Ga/sub 0.4/As layer serves to energize the injected electrons, thereby minimizing their first dead space in the GaAs layer. We show theoretically that the same optimized structures yield optimal breakdown-probability characteristics when the APD is operated in Geiger mode. The steep breakdown-probability characteristics, as a function of the excess bias, of thick multiplication regions (e.g., in a 1000-nm GaAs homojunction) can be mimicked in much thinner optimized Al/sub 0.6/Ga/sub 0.4/As-GaAs APDs (e.g., in a 40-nm Al/sub 0.6/Ga/sub 0.4/As and 200-nm GaAs structure) with the added advantage of having a reduced breakdown voltage (e.g., from 36.5 V to 13.7 V).     

6-k/spl Omega/ 43-Gb/s differential transimpedance-limiting amplifier with auto-zero feedback and high dynamic range

A high-gain, 43-Gb/s InP HBT transimpedance-limiting amplifier (TIALA) with 100-/spl mu/A/sub pp/ sensitivity and 6 mA/sub pp/ input overload current is presented. The circuit also operates as a limiting amplifier with 40-dB differential gain, better than 15-dB input return loss, and a record-breaking sensitivity of 8 mV/sub pp/ at 43 Gb/s. It features a differential TIA stage with inductive noise suppression in the feedback network and consumes less than 450mW from a single 3.3-V supply. The TIALA has 6-k/spl Omega/ (76dB/spl Omega/) differential transimpedance gain and 35-GHz bandwidth and comprises the transimpedance and limiting gain functions, an auto-zero dc feedback circuit, signal level monitor, and slicing level adjust functions. Other important features include 45-dB isolation and 800-mV/sub pp/ differential output.     

Low dark current quasi-Schottky barrier MSM-photodiode structures on n-Ga/sub 0.47/In/sub 0.53/As with p/sup +/-Ga/sub 0.47/In/sub 0.53/As cap layer

The p/sup +/-cap layer was used to fabricate a metal-semiconductor-metal (MSM) interdigitated photodetector on Ga/sub 0.47/In/sub 0.53/As. The measured barrier height was Phi /sub Bn=/0.52 V, the ideality factor n=1.1 and average dark current density 2 mA/cm/sup 2/. A rise time of 45 ps at lambda =1.3 mu m under 2 V bias was measured for an MSM photodiode with 3 mu m finger width and finger gaps and an active area of 100*100 mu m/sup 2/.<>     

Low noise RF MOSFETs on flexible plastic substrates

We report a low minimum noise figure (NF/sub min/) of 1.1 dB and high associated gain (12 dB at 10 GHz) for 16 gate-finger 0.18-/spl mu/m RF MOSFETs, after thinning down the Si substrate to 30 /spl mu/m and mounting it on plastic. The device performance was improved by flexing the substrate to create stress, which produced a 25% enhancement of the saturation drain current and lowered NF/sub min/ to 0.92 dB at 10 GHz. These excellent results for mechanically strained RF MOSFETs on plastic compare well with 0.13-/spl mu/m node (L/sub g/=80 nm) devices.     

Broad-band electronic linearizer for externally modulated analogfiber-optic links

Linearization of analog fiber-optic links using a novel CMOS linearization circuit is reported. A 17-dB suppression of the third-order intermodulation product (IMP3) has been achieved at the modulation index of 49.6 % and over a broad-band frequency range from dc to 1.3 GHz. In an experimental link with a noise floor of -124 dBm/Hz, the spurious free dynamic range (SFDR) is improved by 14 dB from 85 dB/Hz^2/3 to 99 dB/Hz^2/3     

微弱信号非线性检测在随钻电磁波中的应用

在随钻电磁波测井工程中, 随着勘探深度加深, 信号呈现越来越微弱的特性, 有效提取强噪声背景下的微弱电磁波信号对于指导随钻工程勘探具有重要的意义.传统的滤波方法仅滤除带外噪声, 带内噪声不能被很好解决, 针对此问题, 文章设计带外硬件滤波电路和带内基于最小均方算法的可变参数自适应谱线增强(adaptive line enhancer, ALE)算法来构造组合滤波算法.理论分析和仿真研究表明:该组合算法能够提高高动态、低信噪比的微弱电磁波有用信号的估计精度, 有效提高信噪比和抑制工程环境噪声的能力.该组合算法在滤除带外噪声的基础上, 对于带内高斯白噪声抑制能力提高约10 dB, 进一步解决了实际工程问题.     

Broadband microwave noise characteristics of high-linearity composite-channel Al/sub 0.3/Ga/sub 0.7/N/Al/sub 0.05/Ga/sub 0.95/N/GaN HEMTs

We report broadband microwave noise characteristics of a high-linearity composite-channel HEMT (CC-HEMT). Owing to the novel composite-channel design, the CC-HEMT exhibits high gain and high linearity such as an output third-order intercept point (OIP3) of 33.2 dBm at 2 GHz. The CC-HEMT also exhibits excellent microwave noise performance. For 1-/spl mu/m gate-length devices, a minimum noise figure (NF/sub min/) of 0.7 dB and an associated gain (G/sub a/) of 19 dB were observed at 1 GHz, and an (NF/sub mi/) of 3.3 dB and a G/sub a/ of 10.8 dB were observed at 10 GHz. The dependence of the noise characteristics on the physical design parameters, such as the gate-source and gate-drain spacing, is also presented.     

Metal-semiconductor-metal photodetector on p-type In/sub 0.53/Ga/sub 0.47/As

An MSM Schottky barrier photodetector based on p-type In/sub 0.53/Ga/sub 0.47/As suitable for detection in the 0.8-1.7 wavelength range is reported. Aluminium metallisation was used. The large area devices exhibited responsivity of about 0.4 A/W at 1.3 mu m and tau /sub on/>     

In0.53Ga0.47As MSM photodiodes withtransparent CTO Schottky contacts and digital superlattice grading

Metal-semiconductor-metal (MSM) photodiodes with an In_0.53 Ga_0.47As active region were investigated using a transparent cadmium tin oxide (CTO) layer for the interdigitated electrodes to improve the low responsivity of conventional MSM photodiodes with opaque electrodes. CTO is suitable as a Schottky contact, an optical window and an anti-reflection (AR) coating. The transparent contact prevents shadowing of the active layer by the top electrode, thus allowing greater collection of incident light. Responsivity of CTO-based MSM photodiodes with 1-μm finger widths and 2-μm finger spacings and without an AR coating between the electrodes was twice (0.62 A/W) that of a similar MSM photodiodes with Ti/Au electrodes (0.30 A/W). A thin 800 Å In_0.52Al_0.48 As layer was inserted below the electrodes to elevate the electrode Schottky barrier height. A digitally graded superlattice region (660 A) was also employed to reduce carrier trapping at the In _0.53Ga_0.47As/In_0.52Al_0.48As heterointerface which acts to degrade photodiode bandwidth. Bandwidth of opaque electrode MSMs was elevated nearly an order of magnitude over a previous MSM photodiode design with an abrupt heterointerface, whereas the bandwidth of transparent electrode MSM's only improved about five times, indicating resistive effects may be intervening     

Harmonic gain and noise in a frequency-doubling gyro-amplifier

Nonlinear gain in a 34-GHz three-stage frequency-doubling gyro-traveling wave tube (gyro-TWT) has been experimentally studied. The device consists of a thermionic electron gun, TE/sub 01//spl rarr/TE/sub 02/ fundamental gyro-TWT input section, second harmonic TE/sub 03/ intermediate buncher section, and a second harmonic TE/sub 02//spl rarr/TE/sub 04/ complex output circuit. Nonlinear bunching in the electron orbital phase generates harmonics of the input signal in the beam current, which excite the subsequent circuits at the second harmonic frequency. Since the gain is nonlinear, noise or applied sideband signals intermodulate with the carrier generating high-order products in the output. Therefore, it has been suggested that the noise figure of these devices may be unreasonably high. In this study, the complex harmonic transfer characteristics were experimentally measured and compared with calculations based on the assumption that the gyro-amplifier gain can be described, in the narrowband sense, as a classical frequency-doubling circuit. The results show that narrowband intermodulation gain is 6 dB higher than the carrier as predicted in the small signal limit, but as the device reaches saturation the nonlinear products become suppressed with respect to the carrier. Tests on the broadband gain characteristics show that output noise consists of second harmonic shot noise spontaneously excited in the output circuits along with the products of the intermodulation between external noise and the carrier. Good agreement between the experimental results and the calculations is demonstrated.     

1.25-Gb/s Operation of a Spectrum-Sliced Fabry–PÉrot Laser Diode With Intensity Noise Suppression by a Second Fabry–PÉrot Laser Diode

We propose a low-cost solution for the intensity noise suppression in the spectrum-sliced Fabry-Perot laser diode (F-P LD), which is achieved by placing an F-P LD at the receiver region. The F-P LD at the receiver region provides the intensity noise suppression of about 10 dB as well as the increase of the received optical power for the spectrum-sliced optical signal. The Q-factor is improved about 5.9 at a data rate of 1.25 Gb/s. As a result, we successfully demonstrate 10-km error-free transmission at 1.25-Gb/s signal with a transmission penalty of less than 0.5 dB. It is also found that the low spectrum-sliced power of -22 dBm achieves the relative intensity noise level of -112.5 dB/Hz, which is almost independent of the operation current.     

Low dark current GaAs metal-semiconductor-metal (MSM) photodiodes using WSixcontacts

We present the fabrication and characterization of metal-semiconductor-metal (MSM) photodiodes using the same undoped GaAs layer that is used as a buffer layer in the epitaxial structure for GaAs field effect transistors (FET's). To study the dark current mechanism, various metal electrodes used for Schottky contacts are examined. A drastic V-shape relationship between the dark current of MSM photodiode and the Schottky barrier height is found. An extremely low dark current (a few nanoamperes) in the MSM photodiode is obtained by using tungsten silicide as electrode metal. It is concluded that the dark current is a function of a rivalry relation between the electron injection at the cathode and the hole injection at the anode. The internal gain of the MSM photodiode with tungsten silicide contacts is found, and possible mechanisms are discussed. A flat frequency response up to 1.3 GHz is obtained. The results shows the feasibility of MSM photodiodes for use as photodetectors with low minimum detectable power, and their applicability to monolithic integration with FET circuits.