Browse Prior Art Database

Light Activated Semiconductor Switch

IP.com Disclosure Number: IPCOM000096109D
Original Publication Date: 1964-Dec-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Pieczonka, WA: AUTHOR

Abstract

It is often required that a light-activated semiconductor switch operate at very low levels and yet provide and maintain adequately during such operation. Surface problems in such devices create high leakages across their emitter-base junctions which are detrimental to low-level device operation.

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Light Activated Semiconductor Switch

It is often required that a light-activated semiconductor switch operate at very low levels and yet provide and maintain adequately during such operation. Surface problems in such devices create high leakages across their emitter-base junctions which are detrimental to low-level device operation.

To avoid such difficulties, N/+/-type emitter region 10 is buried in P-type wafer 11 which serves as the base region of the switch. Spaced N-type collector regions 12 and 13 are established above the emitter region in the upper surface of the base region. Regions 12 and 13 receive electrical connections 14 and 15. These serve as the input and output connections, respectively, for coupling to the apparatus being controlled.

Light shining on the upper surface of the switch passes through base region 11 and strikes emitter region 10. Minority carriers, then liberated by the emitter region 10, travel to collector regions 12 and 13 through the intervening portion of base region 11 and establish a low impedance path between connections 14 and
15.

Because emitter region 10 is buried, surface problems are avoided and it functions more like an ideal emitter than one which comes to the surface of the device. Also, emitter-base junction J3 is inherently passivated. As a result, the emitter-to-collector transport efficiency beta is higher than that of prior optically activated solid state switches especially at low signal levels. The collector ef...