High-power, TIL-type gate-assisted turn-off thyristors

The work reports the development of trial high-voltage (2000–2500 V), highcurrent (up to 500 A) gate-assisted turn-off (GAT) thyristors based on the novel, double-interdigitated or two interdigitation levels (TIL) gate-cathode configuration. The active cathode area of devices is only 1.7 cm2. The test TIL GATTs were both normal, i.e. using no lifetime killers and gold-diffused at several temperatures. The investigations revealed the high efficiency of the negative current pulse, applied to the gate during the time when the forward anode voltage is being reapplied, in the reduction of the turn-off time t q. Thus, the application of a peak gate current I GR of only 2.5 − 4 A leads to a two- to tenfold decrease of t q in TIL GATTs rated at an anode current i T of 200-500 A. Within the aforementioned levels of i T and at constant value of i GR the dependence of t q on i T was found to be relatively weak. The dependence of TIL GATT performance on gold-doping, junction temperature, n-base thickness and the rate of reapplied anode voltage rise is presented in detail. All trial TIL GATTs possess an excellent turn-on sensitivity accompanied by a high immunity to noise. The results presented reveal the ability of TIL patterns with a relatively coarse geometry to perform multiple-end roles in various modes of operation of high-power GATTs.