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(Color online) Schematic of grating-gated AlN/GaN MOS-HEMTs. The THz wave is incident from top side with the electric field polarized vertically to the gate fingers. The induced polarization field, exciting the plasma wave, is also shown between gate fingers. The band diagram and wave functions of electron are shown at the right side after solving the Possion-Schrödinger equation. The origin Y = 0 is located at AlN/GaN interface. MOS: metal oxide semiconductor.
(Color online) Absorption spectra of AlN/GaN MOS-HEMT with 4 V/−4 V gate bias voltage, three kinds of plasmonic peaks are marked with a (a 1, a 2, a 3), b, and c. The electron density distributions along the y direction for the gated and ungated regions are shown in the inset after self-consistent solving the Poisson’s equation with polarization charge included in each layer.
(Color online) Plasmon-induced electric field distributions along the channel under THz wave excitation with the frequencies corresponding to (a) peak a 1, (b) peak c, and (c) peak b in Fig. 2, where the peak b is from the spectra of grating-gate device with 0.6 μm slits for better visualization.
(Color online) The absorption spectrum of AlN/GaN MOS-HEMT with the effect of phonon-polariton included (solid line) under 4 V gate bias voltage, the one without phonon effect (dashed line) is also shown for comparison. Inset shows the real (solid line) and imaginary (dashed line) parts of complex dielectric constant and the spectral region of “Restrahlen band” is indicated with longitudinal (ω L)-transverse (ω 0) energy splitting.
(Color online) Absorption spectra of AlN/GaN HEMTs with Schttoky gates under −3 V (solid line) and 1 V (dashed line) at temperature lower than 200 K. Two mobility values (3000 cm2/V s and 2000 cm2/V s) are used for indicating the characteristics of plasmon resonance.
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