Frequency dependent CV measurements of GaAs/AlGaAs heterostructures

A procedure is described to determine the carrier density profile in the channel of a FET by evaluating S-parameters measured over a broad frequency range. Applying this method to GaAs/AlGaAs heterostructures, a frequency dispersion of the gate capacitance has been found, which is attributed to a parasitic conducting channel

A monolithic HEMT-amplifier with feedback in coplanar waveguide technology

A monolithic integrated wide-band amplifier is presented, which consists of two 0.3 μm HEMT-stages in GaAs/GaAlAs-Technology. The main signal path consists of a coplanar waveguide, which interfaces conveniently to the HEMT-cells. A feedback circuit with R, L and C connects gate and drain. To close the feedback loop small scale microstrip lines were combined with CPW /1, 2, 4/. Matching is done with a LC circuit at the gate and a combination of transmission line and capacitor at the drain. In addition there are some other passive elements for biasing, which reduce external components to a minimum. All element models were checked with measured data and placed into a CAD-library for easy use in the design process

Novel push-pull chromophores to prepare electro-optic modulators

In recent years, a large number of push-pull organic molecules have been proposed as promising candidates for electronic and optical applications. Generally, the main effort has been focused on the design of chromophores with large first hyperpolarizability values (β); this would result in a wide variety of nonlinear optical (NLO) applications, such as modulators.[1,2] In this work, we report an experimental and theoretical investigation of the NLO properties of novel push-pull systems derived from the dicyanomethylene-4H-chromene (DCM) group. Particular attention will be paid to better understand the molecular and electronic properties of these systems by using vibrational spectroscopic techniques and electrochemistry. Furthermore, these materials have been tested in a silicon-organic hybrid modulator based on an integrated dual-mode interferometer.[3]Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Comprehensive Life Cycle Support for Access Rules in Information Systems: The CEOSIS Project

The definition and management of access rules (e.g., to control access to business documents and business functions) is a fundamental task in any enterprise information system (EIS). While there exists considerable work on how to specify and represent access rules, only little research has been spent on access rule changes. Examples include the evolution of organizational models with need for subsequent adaptation of related access rules as well as direct access rule modifications (e.g., to state a previously defined rule more precisely). This paper presents a comprehensive change framework for the controlled evolution of role-based access rules in EIS. First, we consider changes of organizational models and elaborate how they affect existing access rules. Second, we define change operations which enable direct adaptations of access rules. In the latter context, we define the formal semantics of access rule changes based on operator trees. Particularly, this enables their unambiguous application; i.e., we can precisely determine which effects are caused by respective rule changes. This is important, for example, to be able to efficiently and correctly adapt user worklists in process-aware information systems. Altogether this paper contributes to comprehensive life cycle support for access rules in (adaptive) EIS

8.2 GHz bandwidth monolithic integrated optoelectronic receiver using MSM photodiode and 0.5 μm recessed-gate AlGaAs/GaAs HEMTs

An 8.2 GHz bandwidth monolithic optoelectronic receiver consisting of an MSM photodiode, a transimpedance amplifier, and a 50 Omega output buffer has been fabricated using an enhancement/depletion 0.5 μm recessed-gate AlGaAs/GaAs HEMT process. Successful operation at data rates up to 10 Gbit/s has been demonstrated

An 18-34-GHz dynamic frequency divider based on 0.2-μm AlGaAs/GaAs/AlGaAs quantum-well transistors

The design and performance of a dynamic frequency divider was presented. This digital IC demonstrates the ability of the authors' AlGaAs/GaAs/AlGaAs quantum-well FETs with gate lengths of 0.2 μm. Stable operation was achieved in the frequency range from 18 GHz up to 34 GHz with a power consumption of 250 mW. To the authors' knowledge, this is the best result ever reported for HEMT circuits, and is similar to the frequency limit achieved by use of AlGaAs/GaAs HBTs

7.5 Gb/s monolithically integrated clock recovery using PLL and 0.3 μM gate length quantum well HEMTs

A monolithically integrated clock recovery (CR) circuit making use of the phase-locked loop (PLL) circuit technique and enhancement/depletion AlGaAs/GaAs quantum well high electron mobility transistors (QW-HEMTs) with gate lengths of 0.3 μm has been realized. A novel preprocessing circuit was used. In the PLL a fully-balanced varactorless VCO has been introduced. The VCO has a centre oscillating frequency of about 7.5 GHz and a tuning range greater than 500 MHz. A satisfactory clock signal has been obtained at the bit rate of about 7.5 Gb/s. The power consumption is less than 200 mW at the supply voltage of -5 V

7.5 Gb/s monolithically integrated clock recovery circuit using PLL and 0.3-μm gate length quantum well HEMT's

A monolithically integrated clock recovery (CR) circuit making use of the phase-locked loop (PLL) circuit technique and enhancement/depletion AlGaAs/GaAs quantum well-high electron mobility transistors (QW-HEMT's) with gate lengths of 0.3 μm has been realized. A novel preprocessing circuit was used. In the PLL a fully-balanced varactorless VCO was applied. The VCO has a center oscillating frequency of about 7.7 GHz and a tuning range greater than 500 MHz. A satisfactory clock signal has been obtained at a bit rate of about 7.5 Gb/s. The power consumption is less than 200 mW at a supply voltage of -5 V