High-frequency analysis of SOI Lateral Bipolar Transistor (LBT) structure for RE analog applications

The Lateral Bipolar Transistor (LBT) on SOI substrate for RF analog applications with extrinsic base on the top of the collector n-region is analyzed. The extrinsic base affects f(T) and f(max) in several ways. First, it increases C-BC making it dependent on lithography resolution. Second, depending on collector-base voltage, a collector-base depletion region decreases the effective collector cross-section area thus causing the Kirk effect to occur at lower collector currents. Third, the electrons injected from emitter flows partly through the extrinsic base-collector depletion region increasing the effective transit time. In respect with those effects, the technological parameters are varied and the impact on f(T) and f(max) are analyzed. It is shown that the increase of f(T) can be achieved without sacrificing f(max) considerably only by changing device geometry, still using the same doping profile of the intrinsic transistor region.