A failure mechanism is observed for SiN2-passivated metal semiconductor field-effect transistor (MESFET) devices exposed to fast risetime DC video pulses. The intensity of the pulses is about 33% of the value required to cause single-pulse failure. The failure mechanism, which degrades performance by surface flashover and erosion of the passivation layer, eventually leads to sputtering of the gatesource metallization. The results are observed using a combination of optical, electron, and X-ray micrographs, plus MESFET terminal parameters.IEEE 1992 Microwave and Millimeter-Wave Monolithic Circuits Symposium 1

THE CIRCUIT A low-cost terminal protection device (TPD)The originality of this TPD lies in its simplicemploying only five components has been dem-ity: it uses only five components, which are stanonstrated that is compatible with monolithic mi-dard parts in the MMIC design process. The crowave integrated circuits (MMICs) and suit-broadband circuit is shown in figure 1. Typical able for phased-array applications. Using a values for the resistors are 1 ks1, and for the castandard low-noise, depletion-mode MESFET pacitors, 5 pF. For narrowband operation, a tun-(metal semiconductor field-effect transistor) ing capability can be added to cancel the across a 5042 line, the TPD achieves a small-MESFEiT's capacitive reactance across the 50-SZ signal insertion loss less than 1 dB up to 3 GHz. transmission line. When negative bias is applied, With a single stage, the TPD attenuated 20-W the MESFET gate pinches off the active chanpulses by 14 dB and 500-W pulses by 23 dB. nel, and the input signal passes along the 5042 Spike leakage was less than 0.1 pJ.transmission line with little attenuation. When the bias is off (0 V), the depletion-mode TPD protects the receiver circuits because the FET presents a low impedance across the line. In a the front-end components when the array is unpowered during transport or storage.

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