Optical emission is reported from an n-channel GaAs/AlGaAs bistable fi
eld effect transistor (BISFET), This emission is found to be strongly
correlated with the gate current flowing in the device. Abrupt transit
ions, referred to as optical switchup and switchdown, are observed in
the optical output characteristics as the drain bias is varied, with a
switching ratio in excess of 20 dB. These transitions correspond with
those seen in the drain and gate currents as the feedback loop from g
ate to source switches on and off. The transitions exhibit large hyste
resis, corresponding to that seen in both the drain and complementary
transfer characteristics of the device. The drain voltage at which the
optical transitions are observed, and the associated hysteresis. are
found to be very sensitive to gate bias, particularly in the saturatio
n region of operation. Implications of the optical characteristics for
the carrier flow mechanisms within the BISFET are discussed. Methods
of increasing the optical output efficiency of the device are describe
d.