Transmission properties of grating-gate GaN-based HEMTs under different incident angles in the mid-infrared region.

The absorption tunability of grating-gate GaN-based HEMTs in the mid-infrared region has been confirmed in wide frequency regions. However, the application potential of grating-gate GaN-based HEMTs is limited due to a lack of study on transmission properties under different incident angles. Therefore, this paper studied the transmission characteristics of grating-gate GaN-based HEMTs under different incident angles in the mid-infrared region. By using the optical transfer matrix approach to model the dispersion characteristics in the structure, we found that the stronger plasmon polaritons and phonon polaritons occur in conductive channel and GaN layer. The variation of different incident wave vectors with incident angle affects the plasmon polaritons and phonon polaritons excitation intensities, resulting in the angular tunability transmission properties of grating-gate GaN-based HEMTs. After simulating the electric field distribution in COMSOL, the different transmission properties of grating-gate GaN-based HEMTs occur under different incident angles. Simulated results reveal the excellent angle-selectivity in grating-gate GaN-based HEMTs. The research into these characteristics shows that the structure has a lot of promise for designing mid-infrared angle selection filters, sensors, and other subwavelength devices in the future.