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Design and Characterization of High-Current Optical Darlington Transistor for Pulsed-Power Applications

A high-current and low on-state voltage optical Darlington transistor (ODT) is developed in this paper for high-power applications. The structure of this device includes a two-stage Darlington transistor in which the first stage is triggered optically using an infrared laser of an 808-nm wavelength. The photogenerated current in the first stage drives the second stage of the ODT for current amplification. The ON-state voltage of the proposed two-stage ODT is found to be 1.12 V at 50 A. The results show that a single-pipe laser with a low optical power of 2 W is sufficient to trigger this high-current optical switch. This can give us more flexibility to achieve an optimal tradeoff between the ON-state voltage and delay times. The experimental results show that the ODT has a breakdown voltage of 70 V and can operate at frequencies higher than 10 kHz. Thismakes it potentiallysuitable as an optical gate driver for applications including but not limited to pulsed-power and series-connectionof power semiconductor devices for voltage scaling, and as an auxiliary optical-triggering device for anode- or even gate-currentmodulation of a high-frequency and high-power all-optical emitter turn-OFF thyristor.