Bastian Mottet

Multipactor breakdown prediction in rectangular waveguide based components

In this paper the multipactor power threshold in arbitrary complex components based on rectangular waveguide technology is investigated. The two required computations when studying such a phenomenon have been performed: calculation of the electromagnetic fields inside the component and determination of the multipactor breakdown onset itself. A full multipactor model is described and tested for a particular set of devices for which experimental measurements have been also performed. The good agreement between the predicted breakdown values and the experimental results shows the validity of the approach followed.

A novel system for systematic microwave noise and DC characterization of terahertz Schottky diodes

An automated system is developed to evaluate a large number Schottky diodes for terahertz applications with respect to their dc and noise characteristics using a highly sensitive noise measurement technique for one port devices. An extensive RF switching matrix allows noise characterization of one port devices at selected frequency points over a bandwidth from 2 to 8 GHz. The measurement principle also accounts for the impedance mismatch between the system and the device under test (DUT). Furthermore, the setup includes an automated three-axis nanopositioning system capable of consecutively contacting many Schottky diodes arranged in a honeycomb array. The highly accurate positioning of the DUT allows to create reproducible contacts with the diodes using electrochemically etched whisker tips. The smooth contacting procedure enables several hundred contacts with the same whisker tip. With this system, we evaluate the statistical distribution of dc and noise parameters of Schottky diodes with an anode diameter of 1 /spl mu/m within one honeycomb chip. The system helps in optimizing the production parameters of Schottky diodes for terahertz frequencies.

Micromachined split-block Schottky-diode mixer for 600 GHz

This paper presents simulation results for a 600 GHz micromachined waveguide mixer with integrated horn antenna, a hybrid-integrated planar Schottky diode and IF filter structures on a quartz substrate. In addition to the simulated electrical performance we show approaches for the manufacturing of the split-block mixer by both micro-mechanical milling and silicon etching technology.

Model for the decrease in HBT collector current under DC stress based on recombination enhanced defect reactions

Abstract Based on simplifying assumptions a model is developed to describe decreasing HBT collector current under DC bias stress. The underlying processes are recombination enhanced defect reactions (REDR), namely defect generation and defect annealing. The simplification of the derived equation under particular boundary conditions leads to a form of the Eyring relationship generally employed to describe the decrease in collector current under DC bias stress. Additionally, pulsed tests with an emitter current density of JE=200 kA/cm2 have been performed. The comparison between measured data from these tests and their fit proofs the applicability of the derived equation. Of course this can not be an evidence for the real running physical processes.

A method for HBT process control and defect detection using pulsed electrical stress

Abstract A method for on-wafer reliability characterisation of HBT processes is developed to reveal lifetime deficiencies. Lifetime limiting defects can be generated to investigate the lifetime quality by applying Transmission Line Pulses MP) to the device. Very high current densities can be used to shorten the time of electrical defect generation, while the pulse length is short compared to the thermal time constant of the device. Current and voltage of impulse response and subsequent DC I/V measurements are used for device characterisation between each step of stress which consists of a variable pulse quantity.

Reliability investigations on LTG-GaAs photomixers for THz generation based on optical heterodyning

Optical heterodyne conversion, or photomixing, is a frequency-agile technique that generates continuous-wave radiation at THz frequencies using thin films of low-temperature-grown (LTG) GaAs at high electrical bias. Very high electric fields (>300 kV/cm) and thermal excitation by focused laser illumination require reliability assessments prior to implementation in THz systems. Pulsed electrical stress and DC measurements under optical illumination are used to characterise the reliability of photomixers for THz generation based on optical heterodyning. An improvement in terms of reliability is observed by replacing Ti/Au by Pt metallisation.

Reliability studies on integrated GaAs power-sensor structures using pulsed electrical stress

The transmission line pulse method (TLP) is used to characterise the reliability of bolometric GaAs microwave power-sensors. Two degradation mechanisms are identified during the degradation process of the absorbing NiCr termination, in which the input power is converted into heat. Simulations and a material analysis have been performed in order to characterise the observed degradation mechanisms.

Integrated microwave sensor for cavity-length measurement with sub-millimeter accuracy

A novel measurement procedure using microwaves is presented. The implemented sensor determines the length of a cylindrical cavity (e.g. hydraulic system) with sub-millimeter accuracy in real time. The principle of operation is based on the detection of the resonance-frequency distribution in a cavity resonator.

Reliability investigations on HBV using pulsed electrical stress

First reliability investigations with HBV are presented using pulsed electrical stress. AlGaAs/GaAs material systems as well as InGaAs/InAlAs have been investigated and compared regarding degradation characteristics and mechanisms. Diffusion is proposed to be the responsible degradation mechanism.

The impact of process optimization on planar THz-Schottky device reliability

The technological complexity as well as space-application quality standards require sophisticated process control and optimization for reliability improvement of planar THz-Schottky devices. Degradation mechanisms are initiated using, the Transmission Line Pulse (TLP)-method and monitored as a function of the number of applied pulses. The degradation analysis is performed by IV-measurements on the one side and by Transmission electron microscopy (TEM) on the other side.