Video detection and mixing performance of GaAs Schottky-barrier diodes at 30 THz and comparison with metal-insulator-metal diodes

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Abstract
Video detection experiments from 0.7 to 30 THz and mixing experiments at 30 THz have been performed with GaAs Schottky-barrier diodes and W-Ni metal-insulator-metal (MIM) diodes. Above approximately 12 THz the MIM diode is the more sensitive video detector (a factor of 5–10 at 30 THz). Difference frequencies up to 34 GHz were generated by mixing the radiation of two adjacent CO2 laser lines and a microwave source in a Schottky-barrier diode. The dependence of the mixing signal on different diode parameters (doping density, plasma frequency, cutoff frequency) and on bias current was measured. Compared with MIM diodes at 30 THz the Schottky-barrier diodes are less efficient for mixing (a factor of 104). The results suggest that thermionic emission is the dominant physical mechanism responsible for video detection and mixing at 30 THz.