dimensions did not change the p contact area extends to the edge of the emitter window forming an external base handle and reducing r sub b 39 both the active base and emitter are then implanted through the same oxide window an arsenic emitter was implanted first at 30 kev and a dose of 3 u00d7 10 15 ions cm 2 after annealing boron was implanted at 60 kev and 1 u00d7 10 13 ions cm 2 the individual transistors were mounted in insulated collector four lead to 18 packages to facilitate tuning out package and bonding pad capacitance for the f t measurements comparative f t measurements for the four geometries of fig1 are shown in fig3 for a diffused run and in fig4 for an ion implanted run the epi layer of the diffused run was 4 u03bc thick and had 0 5 ohm cm resistivity the data of fig3 was taken with zero volts collector base basis at a measurement frequency of 400mhz the results for the diffused emitter q32 suggest the following 1 an optimum has been obtained whereby f t is almost independent of current over the range 20 u03bc a to 1 ma 2 the device capacitance has been reduced by a considerable greater amount than that indicated by the nominal dimensions and mask areas of fig1 the epi layer thickness was 0 8 u03bc and its resistivity for.