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The design, fabrication, and characteristics of a 350-V, 100-A buried-gate static induction transistor (SIT) as a power switching device for applications in military and space environments because of its potential for radiation hardness, high-frequency operation, and the incorporation of on-chip smart power sensor and logic functions are described. The potential radiation hardness of this class of devices was evaluated by measurement of SIT characteristics after irradiation with 100-Mrad (2-MeV) electrons and up to 10/sup 16/ fission neutrons/cm/sup 2/. High-temperature operation and the possibility of radiation damage self-annealing are discussed. >

Directly light-triggered, 4000- and 6000-V thyristors were designed, fabricated, and tested to obtain high performance in dI/dt, dV/dt, and photosensitivity. Built-in resistors protected both auxiliary stages during high dI/dt turn-on. The novel use of etched moats to define the resistors was compatible with an optical gate structure that gives high dV/dt and good photosensitivity. No additional processing steps were needed to fabricate these devices, as compared to standard light-triggered thyristors. A record value of 1000 A/µs at 60 Hz was measured on a 6000-V thyristor, and 850 A/µs was safely triggered with only 1.8 mW of light. The dV/dt immunity of the photogate structure measured 4000 V/µs, rising exponentially to 80 percent of 4000 V, V DRM . Thyristors triggered by dV/dt were not destroyed. A new model of resistor heating was combined with the first measurements of the current pulses through both built-in resistors to identify the mechanism responsible for occasional burn-out of the second resistor. The failure mechanism was conductivity modulation in the surface of the resistor during its microsecond on-time caused by thermally generated carriers. The test results confirmed the utility of built-in resistors for high dI/dt performance with minimal light power and for nondestructive dV/dt triggering.

A light-triggered thyristor (LTT) is a four-layer pnpn switch that can be triggered in a different mode than electrically triggered thyristors. For the former, photocarriers generated in the space-charge region activate the pnp transistor first, whereas for electrically triggered thyristors the gate current activates the npn transistor.