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(Color online) (a) Optical microscope images of the detector. Inset: The central gate region showing the isolated antenna (i-antenna) structures. (b) A schematic cross section and an equivalent circuit of the detector.
(Color online) Self-mixing characteristics at 300 K and 77 K. From (a) to (e), different device parameters are given as a function of the gate voltage. (a) The measured source-drain conductance and its derivative. (b) The measured mixing current. (c) The deduced internal conductance and its derivative. (d) The deduced internal mixing current. (e) The measured NEP. The thermal-noise limited NEP at 300 K is marked by the upper dashed line and at 77 K by the lower dashed line. (f) The measured spectral response (full lines). The simulated antenna response (dashed line) and the substrate interference (dash-dotted lines). The refractive index of sapphire was taken to be 3.4. The reflectance at the top interface (air-GaN) is taken to be 45%, while that at the bottom interface is set to be 45% or 90%.
(a) (Color online) The spatial distribution of the mixing factor from a FDTD simulation at 900 GHz compared to the control detector (shown in the inset of the top panel). A color-scale 2D plot for the detector (upper panel) and the control detector (lower panel). Comparison of the measured conductance, (b) its derivative and (c) the responsivity at 300 K.
Measured and fitting parameters at 300 K and 77 K.
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