International Technology Roadmap for Semiconductors 2003の要求清浄度について － シリコンウエハ表面と雰囲気環境に要求される清浄度, 分析方法の現状について －

The past decade has seen rapid progress in research into high-performance Ge-on-Si photodetectors. Owing to their excellent optoelectronic properties, which include high responsivity from visible to near-infrared wavelengths, high bandwidths and compatibility with silicon complementary metal–oxide–semiconductor circuits, these devices can be monolithically integrated with silicon-based read-out circuits for applications such as high-performance photonic data links and infrared imaging at low cost and low power consumption. This Review summarizes the major developments in Ge-on-Si photodetectors, including epitaxial growth and strain engineering, free-space and waveguide-integrated devices, as well as recent progress in Ge-on-Si avalanche photodetectors. Owing to their excellent optoelectronic properties, Ge-on-Si photodetector can be monolithically integrated with silicon-based read-out circuits for applications such as high-performance photonic data links and low-cost infrared imaging at low power consumption. This Review covers the major developments in Ge-on-Si photodetectors, including epitaxial growth and strain engineering, free-space and waveguide-integrated devices, as well as recent progress in Ge-on-Si avalanche photodetectors.

High-performance Ge-on-Si photodetectors

The drive for higher performance in optical fiber systems has renewed interest in coherent detection. We review detection methods, including noncoherent, differentially coherent, and coherent detection, as well as a hybrid method. We compare modulation methods encoding information in various degrees of freedom (DOF). Polarization-multiplexed quadrature-amplitude modulation maximizes spectral efficiency and power efficiency, by utilizing all four available DOF, the two field quadratures in the two polarizations. Dual-polarization homodyne or heterodyne downconversion are linear processes that can fully recover the received signal field in these four DOF. When downconverted signals are sampled at the Nyquist rate, compensation of transmission impairments can be performed using digital signal processing (DSP). Linear impairments, including chromatic dispersion and polarization-mode dispersion, can be compensated quasi-exactly using finite impulse response filters. Some nonlinear impairments, such as intra-channel four-wave mixing and nonlinear phase noise, can be compensated partially. Carrier phase recovery can be performed using feedforward methods, even when phase-locked loops may fail due to delay constraints. DSP-based compensation enables a receiver to adapt to time-varying impairments, and facilitates use of advanced forward-error-correction codes. We discuss both single- and multi-carrier system implementations. For a given modulation format, using coherent detection, they offer fundamentally the same spectral efficiency and power efficiency, but may differ in practice, because of different impairments and implementation details. With anticipated advances in analog-to-digital converters and integrated circuit technology, DSP-based coherent receivers at bit rates up to 100 Gbit/s should become practical within the next few years.

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Coherent detection in optical fiber systems

A repeater and associated method of use includes at least one antenna element for communicating in one direction and at least one antenna element for communicating in another direction. A radio frequency uplink path and a radio frequency downlink path are coupled between the antennas. At least one of the radio frequency uplink path or the radio frequency downlink path includes an adaptive cancellation circuit. The adaptive cancellation circuit is configured to generate a cancellation signal without requiring an injected signal. The cancellation signal, when added to a radio frequency signal in the respective uplink and downlink paths, substantially reduces feedback signals present in the radio frequency signal.

Repeaters for wireless communication systems

Solid-state electronics

A dynamic power amplifier advantageously employed in a wireless terminal for transferring and receiving signals from a base terminal includes an input amplifier adapted to receive an input signal having a given power signal level corresponding to the distance of said wireless terminal to the terminal and adapted to provide an amplifier output signal having a given power output signal level. The dynamic amplifier further includes a power sensor configured to receive the power output signal and to generate a power indication signal corresponding to the power output signal, and a converter adapted to receive the power indication signal in order to generate a biasing signal corresponding to the power indication signal. The biasing signal is applied to the input amplifier so that the operating bias point of the power amplifier varies as a function of the power indication signal.

Linear power amplifier with automatic gate/base bias control for optimum efficiency

An indoor wireless communications system using two-way active-antenna repeaters to distribute signals received from external signal sources within an office, and to extend the range of cordless phone units in use there, is disclosed. The repeaters provide menu-selectable phase-shifting, selectable receiver sensitivity and transmitter power, and selectable signal format conversion to provide added privacy and to prevent interference with communication links in use by third parties within the building. Pattern selection is done by empirical adjustment of an antenna pattern suited to the general floor plan of the area served.

Communication system comprising an active-antenna repeater

An optical integrated circuit comprises a semiconductor body, a semiconductor optical waveguide located on the body, and a bipolar phototransistor located on and optically coupled to the waveguide. In a preferred embodiment, the base region of the transistor is configured to absorb radiation propagating in the waveguide, but the emitter and collector regions are both configured not to absorb the propagating radiation. In a further preferred embodiment, the waveguide is configured to guide the radiation along a propagation axis therein, and the transistor makes an elongated footprint along the waveguide, the footprint being elongated along the direction of the propagation axis. In another preferred embodiment, the footprint is at least three times longer along the propagation axis than along a direction perpendicular thereto.

Monlithically coupled waveguide and phototransistor

A receiver for coherent detection of a PSK modulated optical carrier includes an optical detector, digital-to-analog converters, and a digital module. The optical detector is configured to mix the modulated optical carrier with two phase components of a reference optical carrier and to produce analog output signals representative of optical signals produced by said mixing. The digital-to-analog converters are connected to receive the analog output signals and to produce digital signals from the received analog output signals. The digital module is connected to receive the digital signals and to perform one of compensating the received digital signals for a conjugate phase misalignment between the mixed components, extracting phase of the received digital signals, and estimating a frequency offset between the two carriers from the received digital signals.

Coherent phase-shift-keying

The combination of device speed (f/sub T/, f/sub max/ > 150 GHz) and breakdown voltage (V/sub bceo/ > 8 V) makes the double heterojunction bipolar InP-based transistor (D-HBT) an attractive technology to implement the most demanding analog functions of 40-Gb/s transceivers. This is illustrated by the performance of a number of analog circuits realized in an InP D-HBT technology with an 1.2- or 1.6-/spl mu/m-wide emitter finger: a low phase noise push-push voltage-controlled oscillator with -7-dBm output power at 146 GHz, a 40-GHz bandwidth and low-jitter 40-Gb/s limiting amplifier, a lumped 40-Gb/s limiting driver amplifier with 4.5-V/sub pp/ differential output swing, a distributed 40-Gb/s driver amplifier with 6-V/sub pp/ differential output swing, and a number of distributed preamplifiers with up to 1.3-THz gain-bandwidth product.

Young-Kai Chen

Papers

Linear power amplifier with automatic gate/base bias control for optimum efficiency

Communication system comprising an active-antenna repeater

Monlithically coupled waveguide and phototransistor

Coherent phase-shift-keying

InP D-HBT ICs for 40-Gb/s and higher bitrate lightwave transceivers