Ultrashort Pulse Detection and Response Time Analysis Using Plasma-Wave Terahertz Field-Effect Transistors

• Published in: IEEE transactions on electron devices Vol. 68; no. 2; pp. 903 - 910
• Main Authors: Zhang, Yuhui, Shur, Michael S.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.02.2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Decay; Delay time; Femtosecond pulses; Field effect transistors; Hydrodynamics; Logic gates; Material parameter extraction; Mathematical model; Optical pulse generation; Picosecond pulses; Plasma; Plasma waves; plasma-wave electronics; Plasmons; pulse detection; Pulse duration; Relaxation time; Response time; Semiconductor devices; Shallow water; Short pulses; Step functions; Step response; terahertz field-effect transistors (TeraFETs); Time factors; Transistors; Water waves; Wave propagation; Waveforms
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2020.3043992

We report on the response characteristics of plasmonic terahertz field-effect transistors (TeraFETs) fed with femtosecond and picosecond pulses. Varying the pulsewidth (<inline-formula> <tex-math notation="LaTeX">{t}_{\textit {pw}} </tex-math></inline-formula>) from 10 −15 s to 10 −10 s under a constant input power condition revealed two distinctive pulse detection modes. In the short pulse mode (<inline-formula> <tex-math notation="LaTeX">{t}_{\textit {pw}} \ll {L}/{s} </tex-math></inline-formula>, where <inline-formula> <tex-math notation="LaTeX">{L} </tex-math></inline-formula> is the gated channel length and <inline-formula> <tex-math notation="LaTeX">{s} </tex-math></inline-formula> is the plasma velocity), the source-to-drain voltage response is a sharp pulse oscillatory decay preceded by a delay time on the order of <inline-formula> <tex-math notation="LaTeX">{L}/{s} </tex-math></inline-formula>. The plasma wave travels along the channel like the shallow water wave with a relatively narrow wave package. In the long pulse mode (<inline-formula> <tex-math notation="LaTeX">{t}_{\textit {pw}} > {L}/{s} </tex-math></inline-formula>), the response profile has two oscillatory decay processes and the propagation of plasma wave is analogous to an oscillating rod with one side fixed. The ultimate response time at the long pulse mode is significantly higher than that under the short pulse conditions. The detection conditions under the long pulse mode are close to the step response condition, and the response time conforms well to the analytical theory for the step function response. The simulated waveform agrees well with the measured pulse response. Our results show that the measurements of the pulse response enable the material parameter extraction from the pulse response data (including the effective mass, kinematic viscosity, and momentum relaxation time).