Germanium and silicon transistor structures by the diffused-meltback process employing two or three impurities

The diffused-meltback process for making transistor structures involves growing a crystal containing a donor and an acceptor impurity, cutting the crystal into pellets, melting and refreezing part of a pellet, and then diffusing. Two impurities may be used to produce high-frequency silicon structures. For best results with germanium, three impurities are required for practical reasons. The two and three-impurity cases are analyzed, and illustrated by graphs and numerical examples. Some characteristic transistor parameters are given to show the applicability of the diffused-meltback process for high-frequency devices.