Electromechanical and plasma resonances in two-dimensional electron systems with mechanically floating gates

Abstract

We study plasma effects in a micromachined high-electron mobility transistor (HEMT) with the microcantilever (MC) serving as the gate using the developed model. The model accounts for mechanical motion of the MC and spatio-temporal variations (plasma effects) of the two-dimensional electron gas (2DEG) system in the transistor channel. The MC mechanical motion is described in the point-mass approximation. The hydrodynamic electron transport model is used to describe distributed electron plasma phenomena in the 2DEG system. Using the developed model, we calculated the response function characterizing the amplitude microcantilever oscillations and the output electric signal as functions of the signal frequency and the bias voltage for the devices with different parameters. We find the voltage dependences of the frequency of the mechanical resonance and its damping. In particular, it is demonstrated that the amplitudes of the mechanical oscillations and output electric signal exhibit pronounced maxima at the bias voltages close to the voltage of the 2DEG channel depletion followed by a steep drop with further increase in the bias voltage. We also consider a concept of a resonant detector of modulated terahertz radiation based on a micromachined HEMT. This device can exhibit both the plasma (in terahertz range) and mechanical (in megahertz or gigahertz range) resonances.