Study of lateral scaling impact on the frequency performance of SiGe Heterojunction Bipolar Phototransistor

Abstract : — The influence of the lateral scaling such as emitter width and length on the frequency behavior of SiGe bipolar transistor is experimentally studied.Electrical transistors of different emitter sizesare designed and fabricated by using a commercial bipolar transistor technology. The effect of peripheral current and collector current spreading on electrical bipolar transistor performances are analyzed in regards to the state of the art. Furthermore, the lateral scaling effect on SiGe phototransistor electrical and opto-microwave frequency behavior is studied. The impact of the lateral flow of photo-generated carriers toward the optical opening in phototransistor structure is investigated. Moreover, the two dimensional carrier flow effect on the opto-microwave frequency behavior of the phototransistor is characterized through opto-microwave Scanning Near-field Optical Microscopy (OM-SNOM)measurements, in the course of which the intrinsic parameters such as transit time and junction capacitances are extracted over the surface of the phototransistor.An intrinsic optical transition frequency of 6.5 GHz is measured for 10x10 μm 2 .