Strained Si/Si1−yCy superlattice based quasi-read avalanche transit-time devices for terahertz ultrafast switches


Effects of selective carbon (C) incorporation in silicon (Si) quasi-read-avalanche-transit-time (QRATT) devices are studied through indigenously developed non-linear Strain-corrected-mixed-quantum-tunneling-drift–diffusion-model (SMQTDDM). A superlattice with alternate thin films of strained-Si and comparatively thick layers of Si0.99C0.01 stressors constitutes the active region. Out-of-plane mobility enhancement occurs due to the in-plane biaxial strain at Si/Si0.99C0.01 interfaces. Band offset between Si/Si0.99C0.01results in high injection velocity. Combined effect of strain-engineering and band offset amounts to the application of periodic accelerating pulse along the active region. This subsequently reduces carrier transit-time and results in THz oscillation in Si-ATT-diode. Remarkable RF performance (RF-power ~ \(23.2\times {10}^{8}\) W/m2 at 0.73 THz) of exotic Si-QRATT-devices is reported for the first time. The simulation incorporates quantum-effects, process-induced-strain, parasitic-resistance, thermal-model and inter-sub-band-tunneling in the dispersion relation of the multiple-quantum-wells through a combined solution of Schrodinger–Poisson equations. The theoretical analysis is verified with experimental observations for in-house-fabricated Si-ATT-diodes. QRATT-device-based THz series-shunt switches are further explored.

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The corresponding author, Moumita Mukherjee, wishes to acknowledge Defence (R&D) for the growth of the device. The authors wish to acknowledge Prof. Hans Hartnagel, Emeritus Professor, Technical University, Darmstadt Germany, for providing important suggestions, technical inputs and scientific comments for this work.


This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

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Chatterjee, S., Mukherjee, M. Strained Si/Si1−yCy superlattice based quasi-read avalanche transit-time devices for terahertz ultrafast switches. Appl. Phys. A 127, 155 (2021).

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  • IMPATT oscillator
  • Super-lattice structure
  • Si/SiC material system
  • Strain Engineering