The millimeter wave super-schottky diode detector

The superconductor-Schottky (super-Schottky) diode has been extended to millimeter wavelengths by manipulation of the semiconductor interface, and measurements are reported at 31 and 92 GHz. Diodes were formed by pulse electroplating Pb on 2 × 10¹⁹cm^-3p-GaAs which was etched wth HCl. A thin Au overplate protects the Pb surface from degradation and extends the lifetime of the diode. The diodes were contacted with cat whiskers and mounted across 1/4 height waveguide. The measured diode noise performance is nearly ideal at both 31 and 92 GHz. At 31 GHz, the reported performance is Lc= 8.6 dB, Tmixer= 10K, NEP = 4.8 × 10^-16W/Hz^1/2; at 92 GHz, Lc= 18 dB, 76K < Tmixer< 190K. Therefore this device is a quantum-noise-limited detector at 31 GHz (measured sensitivity of 7 photons) but suffers from excess parasitic losses at 92 GHz. Reducing the loss at 92 GHz will require further engineering of either the semiconductor surface or the contact geometry.