Plastic Deformation of Point Contact Germanium Diode

Dislocation etch pits and other etch patterns due to plastic deformations are observed by the decoration method at electrically formed area on the crystal surface of a point contact germanium diode. The dislocations and other crystal defects are decorated with a lithium impurity. The lithium vapor is diffused into a germanium surface, and crystal defects are delineated by the selective etching of precipitates. The distributions of dislocation etch pits appear in the area of about 70–100 µ in diameter around a point contact and they show the crystallographic orientation <110> on the (111) surface. The dislocation etch pits and other crystal defects are ascribed to the plastic deformation induced in the contact region by an electrical forming. It is confirmed by means of the thermo-emf that the type of conductivity of the formed region changes from an n-type to a p-type. This suggests that dislocations play an important role in the conductivity conversion.