K. Fricke

GaAs monolithic integrated microwave power sensor in coplanar waveguide technology

We present the fabrication technology, theoretical and experimental results of a novel MMIC compatible broadband power sensor. With a 50 /spl Omega/ coplanar waveguide design, integrated AlGaAs thermoelectric sensor and GaAs bulk micromachined membrane for increased sensitivity this sensor is capable of detecting RF power with a sensitivity of 1.1 V/W without any waveguide coupling structure.

A piezoresistive GaAs pressure sensor with GaAs/AlGaAs membrane technology

This paper reports on the technology and performance of piezoresistive pressure sensors that utilize GaAs/AlGaAs membranes for pressure transduction into stress to induce resistance changes of p doped GaAs resistors. We have tested the sensor to differential pressure up to 8*104 Pa and in a temperature range of room temperature up to 433 K.

A new GaAs technology for stable FETs at 300 degrees C

A technology for the fabrication of GaAs devices for operation at 300 degrees C is presented. The high reliability of the devices is mainly due to diffusion barrier of WSi/sub 2/ in the ohmic contacts and to an optimized Si/sub 3/N/sub 4/ passivation. It is shown that MESFETs produced with this technology demonstrate a remarkable stability of their characteristics, even after 100 h of storage at 300 degrees C, and only a little degradation after 100 h at 400 degrees C.<<ETX>>

AlGaAs/GaAs HBT for high-temperature applications

A high-temperature N-p-n AlGaAs/GaAs HBT with a wide-bandgap emitter which can be operated up to a ambient temperature of 350 degrees C is presented. It is demonstrated that a high Al mole fraction of 0.45 in the emitter in combination with a GaAs base layer yields excellent temperature stability. A useful common-emitter small-signal current gain h/sub FE/ higher than 35 was measured in the range between room temperature and 350 degrees C. >

Performance capabilities of HBT devices and circuits for satellite communication

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. >

Thickness‐field excited thickness‐shear resonators in (110) GaAs

The authors present experimental evidence for thickness‐field excitation of thickness‐shear vibrations in GaAs as an example material for zincblende‐crystal semiconductors. The resonance frequency is shown to agree perfectly with theory. This gives an alternative to the composite resonators in miniaturized local oscillators for, e.g., monolithic microwave integrated circuit applications.

A new GaAs power MESFET structure for improved power capabilities

A GaAs microwave power MESFET structure is described that achieves a significant improvement of the gate mode attenuation by incorporating a suitably terminated transmission line parallel to the gate. The reduced attenuation allows a much wider single gate (a factor of 4 is possible) and a corresponding improvement of the total output power. It is shown that this approach leads to higher gain and cutoff frequency. An additional advantage of this MESFET structure is its higher input resistance relative to a device with equal total gate width but more gates in parallel. This results in simpler matching circuits of greater bandwidth. The single-gate structure can be connected in parallel to further increase the total output power. The results of an electrical characterization of the devices are presented, and its advantages and potential application are discussed. >

A novel analytical approach for the nonlinear microwave circuits and experimental characterisation of the nonlinear behaviour of a new MESFET device structure

A novel analytical technique is described based on generalized Volterra series to analyze nonlinear microwave and millimeter-wave circuits and devices. This method is especially efficient for general-purpose CAD (computer-aided design) applications and can be easily incorporated into existing CAD programs. Nonlinear S parameters can be defined using this technique to accurately predict circuit performance or device S parameters at the onset of large-signal excitation. The capabilities of the technique have been demonstrated on MESFET structures, designed to reduce the losses due to the high resistance of the gate electrode. Power and intermodulation distortion measurements have been carried out and good agreement with calculated values has been observed.<<ETX>>

AlGaAs/GaAs/AlGaAs DHBT's for high-temperature stable circuits

High-temperature devices are required for a large number of industrial applications. In order to demonstrate the feasibility of a high temperature operating circuit on GaAs an operational amplifier was designed and fabricated. A corresponding technology for transistors and circuits for operation up to 300/spl deg/C with AlGaAs/GaAs/AlGaAs DHBTs is presented. For the amplifier circuit an open loop gain of 49.5 dB at room temperature and 35.8 dB at 200/spl deg/C was measured, which is in good agreement with the circuit simulation. High temperature stability has been proven by a storage test at 400/spl deg/C over 1000 h for the ohmic contact metallization and 200 h for the transistors.<<ETX>>

Calculation of the power capabilities of HBT amplifiers based an a new physical HBT model

A novel model for the simulation of the microwave power capabilities of HBTs is presented. The model is based on physical analytical of the terminal currents as functions of the base-emitter and base-collector voltages. It takes into account the unequal thermal distribution of temperature for multi-finger HBT devices, the impact ionization, tunnelling, recombination currents etc. From the simulation of multi-finger transistor structures it can be concluded that high thermal device resistances are detrimental for power performance, because of the unequal distribution of temperature and hence base current in the HBT structure. It can also be concluded that the input and output reflection coefficients are insensitive to temperature variation. Finally, it has been shown theoretically and experimentally that the breakdown voltage increases slightly with increasing operating temperature.