W. Brockerhoff

On-wafer microwave measurement setup for investigations on HEMTs and high-T/sub c/ superconductors at cryogenic temperatures down to 20 K

An on-wafer measurement setup for the microwave characterization of HEMTs and high-T/sub c/ superconductors at temperatures down to 20 K is presented. Both S-parameter and noise measurements can be performed in the frequency range from 45 MHz to 40 GHz and 2 GHz to 18 GHz, respectively, using standard calibration techniques and commercial microwave probe tips. Microwave measurements on a pseudomorphic FET and an AlGaAs-GaAs HEMT as well as investigations on a superconducting filter are presented to demonstrate the efficiency of the developed system. >

High-Frequency Measurements on InAs Nanowire Field-Effect Transistors Using Coplanar Waveguide Contacts

In this paper, a 50-μm-pitch coplanar waveguide pattern for on-wafer high-frequency measurements on nanowire FET is used. The contact structure exhibits relatively large parasitic elements in comparison to the intrinsic device making a precise deembedding both necessary and challenging. A single InAs nanowire FET with a large gate length of 1.4 μm possesses after deembedding a maximum stable gain higher than 30 dB and a maximum oscillation frequency of 15 GHz. The gate length scaling of the nanowire transistor is modeled using the experimental transconductance data of a set of transistors and an analytical model. On this basis, both the device performance and the expectation of high-frequency measurements at small gate lengths are discussed.

Direct calculation of the HBT small-signal equivalent circuit with special emphasize to the feedback capacitance

In this paper a new direct evaluation technique for the small-signal equivalent circuit of AlGaAs/GaAs Heterojunction Bipolar Transistors is presented. Based on the known hot and cold measurement technique, all small-signal equivalent circuit elements including the feedback capacitance Cfb can be directly determined in the frequency range from 45 MHz up to 50 GHz without the requirement for any simplification of the corresponding equations.

Sub-Nanosecond Pulse Generation using Resonant Tunneling Diodes for Impulse Radio

The application of resonant tunneling diodes (RTD) for generation of Gaussian-like monocycles and modified Hermite pulses of 2nd order for ultrawideband (UWB) impulse radio is investigated in this paper. A circuit concept employing a pin-photodiode and two RTD based monostable bistable threshold logic elements (MOBILE) is introduced. The circuit generates, depending on a digital optical input signal, arbitrary pulse cycles at the output of the circuit. Based on the measurement result of a single MOBILE, simulations are presented that show the capability of the proposed circuit to generate pulses like single Gaussian pulses, Gaussian monocycles, and 2nd-order modified Hermite pulses. Experimental verification of positive and negative gaussian pulses with a width of 100 ps is demonstrated for a pulse repetition rate of 13.2 Gpulses/s.

RF Investigations on HEMT's at Cryogenic Temperatures Down to 20 K using an On-Wafer Microwave Measurement Setup

Microwave measurements at cryogenic temperatures are very important to investigate the pronounced microwave performance of High Electron Mobility Transistors (HEMT) /1,2/. In order to perform an exact small signal analysis the On-Wafer measurement technique is an indispensable tool. An On-Wafer measurement setup to determine the s-parameters of these devices at temperatures down to 77 K was presented by Laskar et al. /3,4/. However, for the combination of HEMT devices and high Tc superconductors investigations at lower temperatures have to be carried out. For this reason a microwave On-Wafer measurement setup at temperatures from 300 K down to 20 K has been developed. Both, s-parameter and noise measurements, can be performed in the frequency range from 45 MHz to 40 GHz and 2 GHz to 18 GHz, respectively. Using this equipment measurements on pseudomorphic and AlGaAs/GaAs FET will be presented.

Large-Signal Performance of Resonant Tunnelling Diodes in K-Band Oscillators

The large signal behaviour of resonant tunnelling diodes (RTD) in K-band oscillators is investigated in order to optimize the RF-output power of RTD-based voltage controlled oscillators. Circuit simulations based on a scaleable large-signal RTD model are presented and different approaches to increase the RF-power are proposed. A new differential RTD-VCO-circuit in InP RTD/HBT technology with a wide tuning range is introduced, employing balanced RTD-pairs.

Low-Temperature DC and RF Measurement and Modelling of InGaAs-InAlAs Resonant Tunneling Diodes down to 15 K

The influence of temperature on bias dependent small-signal equivalent circuit components of a resonant tunneling diode (RTD) is investigated from 290 K down to 15 K. The RTD model based on bias dependent parasitic elements and the quantum capacitance as well as the quantum conductance is fitted to both, on-wafer DC and RF S-parameter measurements from 45 MHz to 40 GHz over a bias range of 0 V to 0.80 V. For the full temperature range, good agreement between extracted and measured parameters is shown

Investigation of the RF noise behavior of InP-based DHBT with InGaAs base and GaAsSb base

The influence of base layer structure of InGaAs/InP and GaAsSb/InP double heterojunction bipolar transistors in terms of rf-performance and rf-noise behaviour was investigated in detail. With the use of a combined small-signal and rf-noise model it is possible to localize the noise-phenomena to specific device regions. With this knowledge, the transistor can be optimised in terms of the layer-structure achieve improved rf-performance.

A consistent physical model for the gate-leakage and breakdown in InAlAs/InGaAs HFETs

The improvement of the speed performance of Heterostructure Field-Effect Transistors (HFET) by increasing the channel indium content is accompanied by impact ionization degrading the gate leakage and the breakdown behaviour, among others. A physical understanding of the impact of the layer stack and fabrication process is prerequisite for limiting these drawbacks to a certain amount. Here we will provide for the first time a full analytical expression for the leakage current and for the gate-drain breakdown voltage in dependence on the epitaxy layer design and the recess procedure technique. These formulas, based on a physical model including a novel bias dependent velocity approach to simulate the velocity overshoot, are verified with high quality, kink-free InP-based HFETs.

InAlAs/InGaAs/InP dual-gate-HFET's: new aspects and properties

Regardless of the conventional advantages (higher MSG, higher f/sub max/) of the dual-gate HFET-cascode in comparison to its single-gate counterpart, new properties of the three-port device in the InAlAs/InGaAs/InP-system are presented by extended dc- and rf-analysis. The influence of the second gate via V/sub G2S/ on the impact ionization effect is clearly demonstrated. Optimum extrinsic bias conditions offer the possibility to shift impact ionization from the first intrinsic, rf-driven FET to the second FET. S-parameter measurements underline that, at this bias condition, impact ionization does not affect the high frequency behaviour of the whole device. Thus, a drastic improvement of the noise behaviour is demonstrated. In conclusion, the DGHFET-cascode on InP-under the bias condition V/sub G2S/=0 V-instead of its SGHFET-counterpart will be a promising candidate for low noise amplifiers, e.g. in optoelectronic receivers.