The Influence of Fixed Interface Charges on the Current‐Gain Falloff of Planar n‐p‐n Transistors

Abstract

The influence of the fixed interface charge, , at the surface of the base region on the common emitter current gain of planar n‐p‐n transistors has been investigated. Various values of were realized by means of appropriate annealing processes and by using differently oriented substrates. The value of was measured by applying the MOS capacitance‐voltage technique. It was shown that the current gain at low collector currents increases with decreasing interface charge density. To obtain the lowest possible value of , diffusion and oxidation processes were carried out in an MOS furnace. The transistors produced in this way show a current gain which is constant over six decades of collector current.