Performance and reliability of an improved high-temperature GaAs Schottky junction and native-oxide passivation

We have developed a reliable, high-performance, batch-processed, GaAs tantalum Schottky diode (with a gold overlayer) and native-oxide passivated junction¹in a quasi-planar configuration, Varactors and mixers have been fabricated with near-ideal characteristics and state-of-the-art performance. Typically, they exhibit, at 0 V, a junction capacitance near 0.1 pF and a cutoff frequency in excess of 700 GHz when measured at 55 GHz. In a paramp application pumped at 101 GHz, and a signal frequency of 35 GHz, we have obtained a noise figure of 3.5 dB, a gain of 17 dB, and a bandwidth of 600 MHz. When used as frequency doublers (50-100 GHz) and triplers (35-105 GHz), we have realized better than 25-percent efficiency. As mixers, at band, we achieved a single sideband noise figure of 6 dB and the diodes are typically able to sustain short pulse energy (1.5 × 10^-9s) of up to 4.5 ergs with no performance degradation. Reliability tests results to date indicate a MTBF of better than 10⁸h at 100°C and greater than 10⁵h at 200°C. In a commercial application of paramps (3.7-4.2 GHz), these diodes have successfully completed 2.5 million operational varactor hours with no performance degradation.