Nanosecond Time-Resolved Raman Thermography: Probing Device and Channel
Temperature in Pulsed-Operated GaN and GaAs HEMTs

J.W. Pomeroy
1, G. J. Riedel1, M. J. Uren2, T. Martin2, A. Bullen3, M. Haynes3, and M. Kuball1
1H.H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, United Kingdom
2QinetiQ Ltd, Malvern, Worcs WR14 3PS, United Kingdom
3SELEX Sensors and Airborne Systems Ltd., LU1 3PG Luton, United Kingdom
Email: James.Pomeroy@bris.ac.uk, Telephone: +44 0117 954 6886
Keywords: Thermography; Time-resolved; HEMT; Self-heating; AlGaN/GaN; GaAs.

Abstract
We report our recent progress in developing technology to probe the temperature of electronic devices, illustrated for GaN and GaAs-based HEMTs with high time and sub-micron spatial resolution, demonstrating a temporal resolution as short as 10 ns. Understanding transient heating in pulsed-operated HEMTs is important in order to optimize device performance and reliability. It is also important to assess the validity of electrical testing methods. Quasi-adiabatic heating in GaN based devices is identified within the first ~70 ns of device operation, and we find that the temperature reaches as high as 25% of the DC temperature when operated with 200 ns electrical pulses. The technique is also applied to GaAs HEMTs for the first time, demonstrating the versatility of time-resolved Raman thermography.
 
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