Charge-coupled device and charge-injection device imaging

A brief review is given of the advances in solid-state imaging during the last ten years. The issues of surface channel versus buried channel, aliasing versus prefiltering, frame transfer (FT) versus interline transfer (IT) versus charge-injection device (CID), and direct view versus EBIC imaging are discussed. Time-delay-and-integration (TDI) and infrared imaging are discussed. Finally applications are considered.     

Multiple buried channel charge-coupled device

Charge storage characteristics of a vertically stacked multiple p-n layer Si structure, under fully depleted condition, are investigated analytically and the feasibility of operating such structure as the multiple buried channel charge-coupled device (MBCCD) is discussed. Fabrication requirements of the device are outlined and the infleunce of parameter variations on its operational characteristics are described.     

Conductively connected charge-coupled device

A new kind of charge-coupled device, the conductively connected charge-coupled device (C4D) has been built and operated. This device is formed by providing self-aligned, source-drain diffusions (or implants) between adjacent, refractory electrodes of a two-phase, ion implanted-barrier CCD. These implants eliminate the inherently unstable exposed channel region presently found in CCD's with coplanar gates, without resorting to overlapping gates. Shift registers ranging from 16 to 128 b in length were evaluated and in spite of low mobilities (80 cm²/V.s) and low barrier heights (2-3 V), incomplete transfer losses of 0.2 percent per transfer were measured at 1 MHz clock frequency. Fabrication has been demonstrated to be quite compatible with p-channel refractory gate IGFET technology, and because the sensitive interelectrode region of the C4D is heavily doped, these devices should show the same reliability as conventional circuits made with the same technology.     

Experimental performance of the buried-channel acoustic charge transport device

High-speed electron transport is accomplished in a new type of buried-channel charge transfer device which is based on the nonlinear acoustoelectric interaction between large amplitude surface acoustic waves (SAW) and electrons in GaAs. The performance of the acoustic charge transport (ACT) device is enhanced by design improvements which provide precise channel definition and charge injection structures. A transfer efficiency in excess of 0.996 has been measured in an experimental device operating at the SAW clock frequency of 358 MHz.     

The effects of bulk traps on the performance of bulk channel charge-coupled devices

The effects of bulk traps on the transfer effciency and transfer noise in bulk channel charge-coupled devices (BCCD's) are calculated for different charge packet sizes and operating frequencies. These predictions are compared with experimental results and the distribution and density of bulk states in actual devices are thereby measured. The measured low transfer inefficiency of 10^-4per transfer with no intentionally introduced background charge and low transfer noise are shown to be due to a low bulk state density of 2 × 10¹¹/cm³. A detailed comparison of estimated noise in both surface and bulk channel versions of an image sensor and an analog delay line show that BCCD's are very attractive for low-light level imaging but not as attractive for analog signal processing.     

Calculation of potential profiles in the junction charge-coupled device

A method is presented for calculating the potential in a junction charge-coupled device (JCCD) by solving the two-dimensional Poisson equation numerically. This method is used to analyze the possibility of obtaining a smooth potential profile in the transfer channel by a phosphorus ion implantation under the gates.     

Charge-control method of charge-coupled device transfer analysis

An analysis of charge transfer based on the "charge-control" approach has been made for charge-coupled devices (CCD's). A general closed-form equation for the charge transfer efficiency has been obtained that includes the major mechanisms of 1) charge-gradient induced drift, 2) thermal diffusion, 3) an external fringing field, and 4) charge loss due to traps or recombination. When the charge loss and fringing field terms are neglected, the results are in close agreement with the numerical solutions by Strain and Schryer. With the fringing field term included, the closed-form solution compares well with the numerical results by Heller, Chang, and Lo. The effect of charge loss on the transfer efficiency is studied and the temperature dependence of the efficiency, including the temperature dependent surface mobility, is discussed. The effect of a "fat" zero on the diminution of a digital one is discussed with and without charge loss to surface states. It is believed that the charge-control approach not only simplifies the mathematics involved, but also provides practical charge-coupled device and circuit design guides.     

Scanning electron microscope measurements on short channel MOS transistors

Several methods are discussed for measurement of PN junction shapes and channel field conditions in short (≈1 μm gate lengths) MOS transistors. A special test structure for short channel MOS transistor measurements with a scanning electron microscope (SEM) is presented. Secondary electron measurements on lased scribed and angle lapped and stained PN junctions are discussed. Methods for sectional imaging of electrically active, cleaved transistors using electron-beam-induced current (EBIC) are presented. An approximate quantitative model of the EBIC imaging process is presented which allows the calculation of current in a MOS transistor. Using this model the current is shown to be dominated by electric field effects in the depletion region of the transistor.     

Two-dimensional transient analysis of a buried-channel charge-coupled device

An effective method of two-dimensional transient analysis of potential and charge carrier distribution in a buried-channel charge-coupled device (BCCD) operating in storage and transfer modes has been developed with the aid of the finite Fourier transform (FET) technique.The effect of different clocking schemes on charge carrier transfer inefficiency and charge handling capacity are examined and discussed using the method developed. It is also shown that, for a BCCD operating in the storage mode, two-dimensional analysis indicates that the charge handling capacity determined by one-dimensional analysis can result in overestimation, which is misleading.     

Multihop Diversity in Wireless Relaying Channels

Multihop Diversity in Wireless Relaying Channels This paper presents theoretical characterizations and analysis for the physical layer of multihop wireless communications channels. Four channel models are considered and developed: the decoded relaying multihop channel; the amplified relaying multihop channel; the decoded relaying multihop diversity channel; and the amplified relaying multihop diversity channel. Two classifications are discussed: decoded relaying versus amplified relaying; and multihop channels versus multihop diversity channels. The channel models are compared, through analysis and simulations, with the “singlehop” (direct transmission) reference channel on the basis of signal-to-noise ratio, probability of outage, probability of error, and optimal power allocation. Each of the four channel models is shown to outperform the singlehop reference channel under the condition that the set of intermediate relaying terminals is selected intelligently. Multihop diversity channels are shown to outperform multihop channels. Amplified relaying is shown to outperform decoded relaying despite noise propagation. This is attributed to the fact that amplified relaying does not suffer from the error propagation which limits the performance of decoded relaying channels to that of their weakest link.     

STUDY ON MULTICHANNEL PASSIVE MILLIMETER-WAVE RADIOMETER IMAGING AND SUPERRESOLUTION

Multichannel passive millimeter-wave (PMMW) imaging systems have advantage in operating speed, however traditional data processing methods for single channel systems are not applicable for such kind of system. This paper describes an 8-mm multichannel PMMW imaging system, points out the specific problems encountered in multichannel systems, and proposes an experimental multichannel calibration approach in microwave unreflected chamber. In the last superresolution algorithms considering imaging process and some related issues are discussed. The imaging result shows the proposed processing approaches are effective.     

Properties of the MZOS surface wave convolver configuration

The MZOS (metal-zinc oxide-silicon dioxide-silicon) structure is investigated in order to provide a phenomenological understanding of the charge transfer and trapping properties of the zinc oxide layer. Results of fast-ramp measurements of capacitance versus voltage are presented, and on the basis of these results, some biasing and operating procedures are suggested to make effective use of the memory capabilities of this configuration or to avoid unwanted memory effects. A technique for optical imaging is described which offers several advantages over other surface wave imaging techniques. Finally, some potential applications are mentioned.     

A gallium arsenide overlapping-gate charge-coupled device

We have developed a new CCD fabrication process for producing an overlapping gate structure which permits submicrometer control of the gap size while using conventional lithography. This process has been used to fabricate four-phase 16-stage Schottky barrier CCD's on GaAs with charge transfer inefficiencies of less than 2 × 10^-4at a 1-MHz clock rate, indicating that charge loss due to potential troughs between the gates has been essentially eliminated. This control of the gap permits the CCD channel to be of submicrometer thickness, which simplifies the integration of CCD's with high-speed devices requiring submicrometer channel thicknesses.     

1μm栅HEMT DCFL门电路及环形振荡器的设计与实验研究

利用作者提出的HEMT DCFL倒相器直流传输特性及瞬态特性计算机分析的模型,设计并制成了HEMT DCFL门电路及环形振荡器.在电路设计中,重点讨论了E/D NEMT倒相器的电路性能与器件的主要参数(栅长、栅宽、阈压)间的理论关系.工艺研究中,建立了挖栅时沟道饱和电流Is′与阈压值V_(t~h)间关系的理论曲线,并改进了传统化学湿法刻蚀工艺的阈压均匀性及E,D器件电流匹配的控制精度.实验制作了栅长为1μm的增强型和耗尽型HEMT.在1×1mm范围内,阈压偏差小于50mV,E/D倒相器的传输特性为:V_(OH)≈V_(DD),V_(OL)<0.1V,高、低电平转换范围仅0.1V,噪容达0.3V左右.研制的9级、17级环形振荡器,在V_(DD)为0.5V到3.5V范围内都观察到正弦波振荡波形.     

CHISEL programming operation of scaled NOR flash EEPROMs-effect of voltage scaling, device scaling and technological parameters

The impact of programming biases, device scaling and variation of technological parameters on channel initiated secondary electron (CHISEL) programming performance of scaled NOR Flash electrically erasable programmable read-only memories (EEPROMs) is studied in detail. It is shown that CHISEL operation offers faster programming for all bias conditions and remains highly efficient at lower biases compared to conventional channel hot electron (CHE) operation. The physical mechanism responsible for this behavior is explained using full band Monte Carlo simulations. CHISEL programming efficiency is shown to degrade with device scaling, and various technological parameter optimization schemes required for its improvement are explored. The resulting increase in drain disturbs is also studied and the impact of technological parameter optimization on the programming performance versus drain disturb tradeoff is analyzed. It is shown that by judicious choice of technological parameters the advantage of CHISEL programming can be maintained for deeply scaled electrically erasable programmable read-only memory (EEPROM) cells.     

BILOW-simulation of low-temperature bipolar device behavior

The BILOW simulation program for investigating bipolar transistor behavior in the temperature range 77-300 K is discussed. Differences between the numerical approaches required for simulation of low-temperature behavior compared to room-temperature simulation are presented. Efficient numerical models for the physical parameters in the carrier transport equations and Poisson's equation for the temperature range of 77-300 K, including a new highly accurate numerical model for the temperature and doping concentration dependence of carrier mobility, are discussed. A temperature- and doping-concentration-dependent model for apparent bandgap narrowing is also discussed. The internal characteristics of a typical bipolar transistor are simulated over the 300-77 K range. The behavior of current gain β and the unity gain frequency f_T versus collector current density for different temperatures are calculated and discussed     

A device model for the amorphous-silicon staggered-electrodethin-film transistor

A model for the amorphous-silicon (a-Si) staggered-electrode thin-film transistor (TFT) that incorporates gate-voltage dependent mobility for channel current and space-charge-limited current effects for the source and drain contacts is discussed. This model is in excellent agreement with TFT data over a wide range of applied voltages and for various channel lengths. For the devices measured, the TFT current depends more sensitively on effective channel mobility than on space-charge-limited current through the a-Si layer, but the latter is responsible for current crowding at low drain voltage. Because of the two-dimensional current flow under the contacts, their equivalent lumped element model exhibits a different power law behaviour than that for one-dimensional current flow in an n⁺-i-n⁺ structure. It also shows that a peak in the differential conductance curve at low drain voltage is a sensitive indicator of current crowding and implies a superlinear equivalent lumped element in series with the intrinsic TFT     

Experimental system prototype of a portable, low-cost, C-scan ultrasound imaging device.

A system prototype of a future compact, low-cost medical ultrasound device is described and presented with experimental results. The prototype system consists of a 32 x 32 element, fully sampled 2-D transducer array and a printed circuit board (PCB) containing 16 custom "front-end" receive channel integrated circuits (ICs) with analog multiplexing and programmable logic. A PC that included a commercially available data acquisition card is used for data collection and analysis. Beamforming is performed offline using the direct sampled in-phase/quadrature (DSIQ) algorithm. Pulse-echo images obtained with the prototype are presented. Results from this prototype support the feasibility of a low-cost, pocket-sized, C-scan imaging device.     

A digital DS spread-spectrum receiver with joint channel andDoppler shift estimation

A digital spread-spectrum receiver design is presented for communication over multipath channels with severe Doppler shifts. The characteristics of the underwater channel relevant to spread-spectrum system design are discussed, and a channel model for short-range communications (less than 10 km) is defined. The receiver considered uses a digital coherent RAKE combiner, coupled with an extended Kalman filter (EKF)-based estimator for channel parameters and pseudonoise code delay. Receiver performance is evaluated by computing average bit-error rate (BER) versus iterations of the EKF joint estimator, using both fixed and time-varying channels. It is shown that the BER obtained using the EKF joint estimator closely tracks the optimum BER obtained when the channel, delay, and Doppler parameters are known exactly. Finally, the Cramer-Rao lower bound for time-invariant joint channel, delay, and Doppler estimation is derived, and compared with the ensemble averaged mean-squared error of the EKF estimator