COHERENT TRANSISTOR

We consider the high-frequency operation of an abrupt-heterojunction t ransistor with ballistic transport in the base. The coherent regime ar ises at temperatures low enough compared to the injection energy, that the injected minority carriers form a nearly collimated and monoenerg etic beam. The coherent transistor can have both the current gain and the power gain at frequencies far above the conventional cutoff. The e xtended frequency of an intrinsic transistor is limited by the dispers ion in the minority-carrier times of flight across the base, rather th an the average time of flight itself. The unilateral gain U calculated for an exemplary heterostructure, including the parasitics, demonstra tes an active behavior of the coherent transistor in extended frequenc y ranges.