Improvements in rectifying semi-conductor bodies

摘要

1,096,777. Semiconductor devices. ALLM€NNA SVENSKA ELEKTRISKA A.G. May 13, 1965 [May 15, 1964], No. 20219/65. Heading H1K. A PNPN structure for use in a controlled rectifier comprises heavily doped P and N outer zones separated by a more lightly doped middle section comprising a central layer for which the product of thickness and impurity concentration is less than 1012 atoms/cm2 with layers at its opposite faces, between 1 and 20% of the thickness of the central layer, for which the same product lies between 2 x 1011 and 2 x 1012 atoms/cm2. If the intermediately doped layers are of opposite conductivity types the three layers alone constitute the middle section but if they are of the same type a fourth layer is disposed between one of the intermediately doped layers and the outer zone. A typical device (Fig. 5) comprising such a structure is made by epitaxially depositing N-type silicon layers 34, 35, 50Á thick on opposed faces of an N type silicon wafer doped with 4 x 1012 donor atoms/cc., diffusing gallium into the layers to form P regions 36, 38, and forming the outer N+ and P+ zones 37, 40 by alloying gold-antimony 39 and aluminium 40 respectively to these regions. In the last mentioned process a molybdenum electrode 42 is attached. Epitaxial deposition is from a mixture of hydrogen, silicon tetrachloride, and the tri- or pentachloride of phosphorus. The zone dimensions and doping of this and other suitable structures are detailed in the Specification.