Low barrier height ion implanted X-band silicon Schottky barrier mixer diodes

Platinum - n type silicon Schottky barrier diodes have demonstrated low noise figure and high burnout performance to both nanosecond and microsecond wide RF pulses at X and Ku-band frequency. Because of high barrier height, they require high local oscillator power to operate as mixers and, therfore, have a limited use. Various high power radar systems have limited local oscillator power but also require high burnout mixer diodes to withstand leakage from protecting limiters. This paper describes the ion implantation technique to reduce the barrier height of platinum-silicon and nickel-silicon Schottky barrier X-band mixer diodes. Low barrier height Schottky barrier diodes have been developed by implanting Antimony in n-type epitaxial silicon at 6 keV-30 keV with fluences between 5× 10¹¹- 6 × 10¹³cm^-2. The metallization systems utilized were Pt-Ti-Mo-Au and Ni-Au where Pt or Ni was the Schottky barrier. Ion implanted silicon, Ni-Au Schottky diodes exhibited a barrier height reduction of .1 eV, a noise figure of 7.5 db at .75 mW power level.