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We present detailed numerical analysis of the Dyakonov–Shur (DS) plasma instability in a DC biased graphene field-effect transistor (FET) with the gate shifted with respect to the middle of the transistor conducting channel. We show that the geometric asymmetry is sufficient to trigger the DS instability in the two-dimensional electron gas in the transistor channel. We demonstrate sustained plasma oscillations in the instability end point and analyze the properties of these oscillations for different positions of the gate and at different values of other physical and geometric FET parameters. The obtained results show the possibility of designing a tunable on-chip source of terahertz electromagnetic radiation based on the graphene FET with shifted gate.

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Terahertz (THz) plasma oscillations represent a potential path to implement ultrafast electronic devices and circuits. Here, we present an approach to generate on-chip THz signals that relies on plasma-wave stabilization in nanoscale transistors with specific structural asymmetry. A hydrodynamic treatment shows how the transistor asymmetry supports plasmawave amplification, giving rise to pronounced negative differential conductance (NDC). A demonstration of these behaviors is provided in InGaAs high-mobility transistors, which exhibit NDC in accordance with their designed asymmetry. The NDC onsets once the drift velocity in the channel reaches a threshold value, triggering the initial plasma instability. We also show how this feature can be made to persist beyond room temperature (to at least 75 °C), when the gating is configured to facilitate a transition between the hydrodynamic and ballistic regimes (of electron− electron transport). Our findings represent a significant step forward for efforts to develop active components for THz electronics.

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