Base current of I/sup 2/L transistors

For the I/SUP 2/L n-p-n transistor, a method is presented which allows the base current to be split into various components. This has been achieved by comparing, at a fixed emitter-base voltage, the base current of I/SUP 2/L devices, different in geometry. Several precautions against parasitic effects are described. The measurements have been carried out in the emitter-base voltage range of 540-650 mV. Mathematical expressions are derived for the measured current densities and are compared with theory. It is demonstrated that bandgap narrowing effects in the heavily doped regions of the device have to be taken into account in order to explain the difference between experimental values and theory. Furthermore, it is shown that the experimentally determined base current of a four-collector I/SUP 2/L gate is in good agreement with the calculations.