A transistor utilizing an epitaxially grown base and collector region

With the advent of the techniques for growing epitaxial films of silicon and germanium, the question naturally arises as to how the method compares to a well-established technique such as diffusion. The present commercial epitaxial transistors consist of thin epitaxially grown collector regions into which the base and emitter are diffused. By controlling the impurity concentration during growth, it is theoretically possible to produce a completely grown epitaxial structure. One must then decide what advantages, if any, accrue. An attempt has been made to obtain a partial answer by growing the collector and base region and then diffusing in the emitter. This has the possible advantage of eliminating the long base diffusion which is required in the conventional "\´epitaxial" structure. At the same time, it gives a considerable amount of information about the properties of grown junctions and the state of crystalline perfection the base region. Data will be given comparing these "grown base" devices with the conventional high preformance double-diffused epitaxial device, 2N834. The effects of base doping and geometry will be discussed.