Polarization Properties in GaN Double-Channel HEMTs at Mid-Infrared Frequencies

The polarization properties of grating-gate GaN-based high electron mobility transistors in the mid-infrared region have been investigated. However, due to the lack of research on the absorption characteristics of double-channel (DC) HEMTs in the mid-infrared band, the application potential of GaN-based HEMTs is limited. Therefore, this paper studied the absorption spectra of single-channel (SC) and double-channel grating-gate GaN-based HEMTs at different gate lengths in the mid-infrared region by using the Drude and Lorentz dispersion to model the conductive channel and GaN layer. Variation of different gate lengths changes the duty cycle, which affects the plasmon polarization and phonon polarization intensities. Using the finite-difference time-domain (FDTD) method, it was indicated that the symmetrical and asymmetrical plasmons are induced by the surface polarization field. By changing different gate lengths and sheet electron densities, significant plasmonic enhancement effects can be observed in DC-HEMTs. These promising findings suggest that the DC-HEMTs can be used to design multi-channel mid-infrared detectors, multi-channel mid-infrared modulators, and other multi-channel devices in the future.