AlGaInAs/InP 1.5 μm MQW DFB laser diodes exceeding 20 GHzbandwidth

Buried mushroom multiquantum well DFB laser diodes with compressively strained GaInAs quantum wells and asymmetric confinement layer design are fabricated with a combined MBE/MOCVD technology. Packaged devices exhibit high -3 dB IM bandwidths for very low bias levels and a record bandwidth for this material system of 21 GHz     

InGaAs/InP thermoelectric infrared sensor utilizing surface bulkmicromachining technology

A novel InGaAs/InP micromachined thermoelectric sensor is presented. The key features of the reported sensors are the high thermal resistivity and high mobility of InGaAs lattice matched to InP, combined with a value of Seebeck coefficient that is acceptable for such applications. The anisotropic and selective surface bulk micromachining properties of this material system were successfully applied to devices aligned along the (010) orientation on a [100] InP wafer and the details of the technology used for this purpose are presented. A responsivity of 184 V/W and a relative detectivity of 7.1×108 cm Hz^-1/2/W have been demonstrated using this new sensor approach     

Performance capabilities of HBT devices and circuits for satellitecommunication

The heterojunction bipolar transistor (HBT) performance is studied, with emphasis on its possible utilization in satellite power amplifiers. After a review of the requirements of satellite power amplifiers, the suitability of HBTs is discussed in depth, including the output power capabilities, the realizable power-added efficiency and linearity, reliability considerations, and circuit aspects. Models and simulation tools for HBTs in power amplifiers are discussed, and the results obtained so far are given. A comparison of realized HBTs and various FET devices and circuits demonstrates that the HBT is a promising device for applications in satellite power amplifiers. The HBT will be a preferable device for microwave power amplification if the problems concerning the reliability can be solved, and further investigations will be performed to obtain larger devices with higher rated output power     

Engineering at German universities

Changes in modern society have strongly affected German universities. In particular, a large percentage of the younger generation is following a degree course, especially, in engineering. The result is overcrowding. Discussions are taking place on how to handle large student numbers more efficiently without incurring a drop in academic standards. In view of this latter requirement, it is generally accepted that much importance must be attached to all professors retaining a direct involvement in research despite funding problems. Accordingly, recent developments in UK universities, where teaching without a research component is sometimes becoming a reality, are viewed in Germany with some astonishment. Therefore, one aim of this paper is to contribute to the important discussion of the idea of the European University     

AuGeNi migration affected by operating conditions of GaAs FETs

The metal migration from positively biased AuGeNi planar-electrode edges as known to take place rapidly when strong electric fields exist, is found to be enhanced by increased temperatures and other effects, such as photon bombardment and an electrical discharge in air. The voltage threshold of metal bridge formation between co-planar electrodes is therefore affected by the thermal properties of the chip and its heat sink. It is proposed that the parameters for a theory of field-enhanced surface diffusion are systematically measured, particularly also for various types of GaAs surfaces, in order to maximise device life times.     

Pulse gain and analogue-to-pulse conversion by Gunn diodes

20dB current gain and 9 dB power gain have been achieved for single-pulse operation with Gunn diodes in the resistive mode. A new analogue-to-pulse convertor is described. it is verified experimentally for six levels.     

Wave-theoretical analysis of signal propagation on FET electrodes

A wave-theoretical analysis of MESFET electrode structures is undertaken, incorporating losses of both the semiconducting layer and the finite conductivity of the electrodes. It is shown that the relevant microwave FET mode has slow-wave properties with a slowing factor of about 6.     

New measurement method of Gunn-diode impedance

Using a suitably designed cavity, the negative conductance of X band Gunn diodes is derived from oscillation buildup characteristics when a steep bias voltage step is applied. By this method, a quick assessment of the diode negative conductance as a function of r.f. voltage amplitudes can be made.     

Memory loop with Gunn-effect pulse diodes

The successful operation of a Gunn-effect memory loop is reported. It consists of two Gunn diodes operating in series.     

Recommended Procedures for Simplified Inelastic Design of Steel I-Girder Bridges

This paper presents summary recommendations pertaining to new AASHTO procedures for simplified inelastic design of steel I-girder bridges. First, key developments are summarized that lead to the proposed inelastic design approach. The paper then outlines a set of equations that provide an improved characterization of the inelastic moment-rotation response for a wide range of I-beams and plate girders. Effective plastic moment predictions based on these equations are combined with the recently proposed design method, resulting in greater accuracy and simplicity of the proposed approach. The ease of use of the resulting procedure is illustrated by a design example.