GB848331A - Improvements in or relating to methods of manufacturing alloy p-n junctions in germanium - Google Patents

Abstract

A method of making a PN junction comprises melting a donor or acceptor impurity on to a P or N type germanium body by heating to below 450 DEG C. in the presence of a halogen in elemental or combined form and subsequently heating to a higher temperature above 350 DEG C. at which temperature the vapour pressure of the halogen or halogen compound is at least 10 mm. of mercury. In one example a transistor is made by applying small beads of indium to opposite sides of a 150m thick disc of N type germanium, heating in a stream of dry hydrogen to 300 DEG C. and then for several seconds introducing hydrochloric acid into the stream so that the indium wets the germanium but does not readily dissolve it. A base contact is simultaneously secured by tin solder. Subsequently nitrogen containing a trace of oxygen is introduced and the temperature increased to 600 DEG C. so that alloy electrodes are formed and the hydrochloric acid evaporated. Halogens or other halogen-hydrogen acids may be used instead of hydrochloric acid. In an alternative method the beads of indium are moistened in a saturated solution of pyridine hydrochloride in water before being applied to the germanium wafer, in which case the introduction of the hydrochloric acid is unnecessary. Halogen hydrogen molecular complexes of organic compounds e.g. aniline chlorhydride, dimethylaniline chlorhydride, and guanidine chloride, or indium chloride may be used instead of pyridine hydrochloride for wetting the beads.