MODELING AND CHARACTERIZATION OF SIPOS EMITTER AND QUASI-SIS EMITTER BIPOLAR-TRANSISTORS

SIPOS emitter bipolar transistors have been fabricated with a common-emitter current gain of 8000 and a figure of merit (gain divided by intrinsic base sheet resistance) of 200 (kOMEGA/sq)-1. The high gain is attributed to a relatively low interface recombination velocity of the emitter contact, as measured by photo-induced microwave reflectometry. The cutoff frequency is measured to be 250 MHz, the low value attributed to a large emitter contact resistance of the SIPOS emitter. We suggest that a new figure of merit-transconductance divided by emitter resistance-should be considered for the comparison of the high-frequency performance of high emitter efficiency bipolar transistors. A quasi-SIS emitter bipolar with a poly-Si emitter and undoped SIPOS as an interfacial layer was also fabricated. By incorporating a field-enhancement factor in the SIPOS, the behavior of this transistor is successfully explained by a SIS emitter model. The ideality factor ratio in the Gummel plot is attributed to the different barrier heights of electrons and holes at the SiO2/n-Si interface.