Breakover phenomena in field-controlled thyristors

The occurrence of breakover in the forward-blocking anode current-voltage characteristics of field-controlled thyristors is analyzed. It is demonstrated that this breakover occurs due to gate current flow which causes a debiasing of the gate potential in the presence of any series gate resistance. Based upon this mechanism, analytical expressions have been derived which describe the anode current-voltage breakover characteristics. These theoretical expressions have been found to be in very good agreement with the measured data obtained from asymmetrical field-controlled thyristors fabricated with various device thicknesses. From the analysis presented in this paper, it can be concluded that the occurrence of breakover in the forward-blocking characteristics of field-controlled thyristors can be minimized by ensuring low series gate resistances which biasing the devices and by using gate bias voltages well in excess of the minimum value required to block any desired anode voltage.