Keysight-led system characterises InP transistors from near-DC to 250GHz

Keysight Technologies, the University of Glasgow, the UK’s National Physical Laboratory and MPI Corporation have demonstrated on-wafer transistor characterisation from near-DC to 250GHz in a single measurement sweep. The system was used to measure indium phosphide high-electron-mobility transistors without changing probes or dividing the measurement into separate frequency bands. This avoids the discontinuities that can be introduced when results from different test configurations are joined together. The test arrangement combines a Keysight PNA-X network analyser, a single-sweep 250GHz frequency extender, source-measurement equipment and broadband wafer probes. The complete measurement is performed with one probe touchdown. Keysight’s NA5307A extender supports calibrated S-parameter measurements across a continuous range extending to 250GHz. The product provides a system dynamic range of at least 110dB between 20GHz and 170GHz, at least 105dB from 170GHz to 220GHz, and at least 75dB between 220GHz and 250GHz. The research team used the system to collect broadband measurements from InP HEMTs. These compound-semiconductor devices are used in very-high-frequency amplifiers, communications equipment, sensing systems and scientific instrumentation. Compact transistor models require consistent measurements across the intended operating range. Differences between calibration methods, probes or test fixtures can otherwise create artefacts that must be separated from the behaviour of the device itself. The partners said the continuous measurement method could support more reliable model extraction for sub-terahertz devices. The system also allows DC bias conditions to be applied while the RF measurement is made. The work brings together transistor fabrication at the University of Glasgow, measurement expertise from NPL and the Max Planck Institute, and broadband instrumentation from Keysight.