Tunable far-IR detectors/filters based on plasmons in two-dimensional electron gases in InGaAs/InP heterostructures

Abstract

Plasmons can be generated with photons in the two dimensional electron gas (2-deg) of high electron mobility transistors (HEMTs). Because the plasmon frequency at a given wavevector depends on sheet charge density, a gate bias can tune the plasmon resonance. This effect allows a properly designed HEMT to be used as a voltage-tunable narrow-band detector or filter. This work reports on both the theory and design of such a device in the InP materials system and discusses its potential uses. By using a sub-micron grating to couple incident radiation to a high sheet charge 2-deg, a minimum detectible wavelength of roughly 26 microns is obtained. Fabrication issues, terahertz response, and tunability are discussed. Because of its small size, this novel device could find use in spaceborne remote sensing application.

Plasmon resonance response to millimeter-waves of grating-gated InGaAs/InP HEMT

“…Smaller t/a results in lower total transmittance but stronger coupling to plasmons, as evidenced by deeper absorption lines in comparison to the baseline. Expansion of the curves vertically reveals another feature already reported [8], namely, that the second-order mode disappears when t/a = 0.5. Note that the position of the resonances is independent of t/a.…”