Reduced low-frequency noise Schottky barrier diodes for terahertz applications

The Schottky barrier diode remains an important device for detecting and mi xing at terahertz frequencies, particularly in plasma diagnostics and atmos pheric remote sensing. In plasma diagnostics, plasma density is monitored u sing a receiver with an IF typically below 10 MHz, thus it is critical to r educe low-frequency excess noise to improve sensitivity. We present here a submicrometer Pt/GaAs diode fabrication process that has resulted in a sign ificant reduction in low-frequency noise over that of commercially availabl e devices. Noise performance is optimized by establishing an even distribut ion of gallium and arsenic (stoichiometric surface) at the contact surface. The effects of different SiO2 deposition and etching techniques are also c ompared, Diodes fabricated with the optimized procedure have exhibited a si gnal-to-noise ratio that is three times higher than that of commercially av ailable diodes at 0.9 THz using an IF of 80 kHz, as well as competitive per formance at 1.4 THz with an IF in the gigahertz range.