Browse Prior Art Database

Light Modulator

IP.com Disclosure Number: IPCOM000092007D
Original Publication Date: 1968-Aug-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

McGroddy, JC: AUTHOR [+2]

Abstract

High field domains, which are nucleated at a cathode and propagate to an anode, can be produced in a number of semiconductor materials under the proper conditions. As a domain propagates in the semiconductor body, which is usually N-type, it produces in the material, due to avalanche breakdown, a high concentration of holes.

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Light Modulator

High field domains, which are nucleated at a cathode and propagate to an anode, can be produced in a number of semiconductor materials under the proper conditions. As a domain propagates in the semiconductor body, which is usually N-type, it produces in the material, due to avalanche breakdown, a high concentration of holes.

In germanium, which can be prepared in pure form, these holes are not trapped and are drawn from the device at an orderly rate by the negative voltage at the cathode. The portion of the body in which the holes exist is, by free hole absorption, highly absorptive of infrared light. Therefore, light applied to the device as in A is modulated in a scanning fashion by the holes produced by the domain.

In B, there is an oscillator circuit for modulating light in which external circuitry is provided. Such controls the rate at which domains are propagated in the semiconductor body so that a new domain is not nucleated until the holes produced by the previous domain are swept out at the cathode. This timing arrangement follows from the fact that the portion of the semiconductor body in which the holes are present has a higher conductivity than the remaining portion of the body. Thus it is possible that a new domain, if allowed to nucleate immediately after the previous domain is extinguished, might be nucleated at the edge of the high conductivity portion of the body, portion containing holes, rather than at the portion adjacent the c...