Effects of the Collector Depletion Layer Width on the Characteristics of Drift Transistor

Abstract

Electric characteristics of the drift transistors having different width of nearly intrinsic base region between a given diffused layer and the collector region are experimentally investigated. It is found that the above width, which usually corresponds to that of the collector depletion layer at low level operation, has appreciable effects on the current dependence of the carrier transport characteristics represented by such parameter as fT or β0. These results are found to be explained fairly well in the light of the theory presented by C.T. Kirk who postulates the expansion of the neutral base width into the nearly intrinsic region at high level operation. It is also pointed out that more involved considerations on the transit velocity of carriers across the depletion layer seem necessary for the complete interpretation of the results on fT.