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Photosensitive Transistor

IP.com Disclosure Number: IPCOM000096070D
Original Publication Date: 1964-Nov-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Leff, J: AUTHOR [+2]

Abstract

Conventional planar transistors are inherently photosensitive and can be treated to greatly enhance their photosensitivity. For example, in the production of an NPN silicon planar transistor, this can be accomplished by evaporating a material such as aluminum films 10 and 11. Such evaporation is over the entire base and emitter regions of the flat upper face of the transistor to within about 0. 5 mil of the emitter and base junctions 12 and 13, as in A.

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Photosensitive Transistor

Conventional planar transistors are inherently photosensitive and can be treated to greatly enhance their photosensitivity. For example, in the production of an NPN silicon planar transistor, this can be accomplished by evaporating a material such as aluminum films 10 and 11. Such evaporation is over the entire base and emitter regions of the flat upper face of the transistor to within about 0. 5 mil of the emitter and base junctions 12 and 13, as in A.

The films are then alloyed with the underlying semiconductor region. Then, the aluminum is completely etched away except for small areas 14 and 15, as at
B. These areas receive emitter and base connections 16 and 17 in a subsequent operation. The etching is accomplished with an aqueous solution of sodium hydroxide using conventional photoresist masking and etching techniques.

The etching operation not only exposes the silicon surfaces 18 and 19 but also roughens them so that they no longer constitute smooth reflecting surfaces while at the same time greatly increasing their surface areas. The uneven areas of surfaces 18 and 19 are now nonreflecting and, when irradiated, afford currents about five to ten times greater than corresponding devices having smooth exposed surfaces.

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