Light-triggering phenomena on thyristors with an n-emitter layer over the light-sensitive gate area

Turn-on phenomena of a light-activated thyristor are analyzed using a one-dimensional numerical model that consists of the full set of semiconductor device equations, including the optically generated current and the effect of the shorted emitter. Results indicate that the photocurrent I
p
is induced by photovoltaic effects of the
n_{E}-p_{B}
junction and that its flow is in the reverse direction of the anode current I
A
. Consequently, I
p
circulates through the p-base, the short path placed across the
n_{E}-p_{B}
junction and the n-emitter resulting in a contribution to the light triggering, in addition to that of I
A
caused by the conventional
P_{B}-n_{E}-p_{E}
transistor action. In order to confirm the predicted behavior of the photocurrents, light-triggered 4-kV devices were fabricated. The experimental results thus obtained confirm the conclusions drawn from the model analysis.