Surface-immune transistor structure

A new transistor structure in which the base region is brought to an external surface through the central region of the collector is found to be characterized by a high degree of minority-carrier conservation and surface immunity. Silicon power transistors of this new geometry have also been found to exhibit greatly lower saturation and base resistance than comparable units of conventional structure. Values as low as 0.4 and 3.5 ohms, respectively, are obtained with surface-immune transistors, while 2.5 and 56 ohms are obtained with comparable units of conventional structure. The new structural geometry seems to offer great promise for improving commercial silicon-power-transistor performance. Furthermore, the new structure should be very helpful for transistors made of new material such as gallium arsenide in which surface recombination tends to be extremely high. The importance of the structure should be less, on the other hand, for transistors made from germanium, in which surface recombination can be very low.