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Optically Addressable Heterojunction Storage Device

IP.com Disclosure Number: IPCOM000075067D
Original Publication Date: 1971-Jul-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Van der Meulen, YJ: AUTHOR

Abstract

In the investigation of electrooptical devices with a view toward achieving high-bit densities in computer memories, there has been produced a ferroelectric-photoconductive (FE/PC) device. In this latter device, information is stored as the positive or negative polarization state of a particular small area of ferroelectric material. There has also been considered the combining of a photoconductive layer, as used in the FE/PC device, with a heterojunction switch which may consist, for example, of a layer of zinc selenide (ZnSe) which is grown on a germanium (Ce) substrate to achieve a similar type of memory sandwich. The device wherein the photoconductive layer and the heterojunction switch are combined differs in operation, in some particulars, from the FE/PC sandwich.

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Optically Addressable Heterojunction Storage Device

In the investigation of electrooptical devices with a view toward achieving high-bit densities in computer memories, there has been produced a ferroelectric-photoconductive (FE/PC) device. In this latter device, information is stored as the positive or negative polarization state of a particular small area of ferroelectric material. There has also been considered the combining of a photoconductive layer, as used in the FE/PC device, with a heterojunction switch which may consist, for example, of a layer of zinc selenide (ZnSe) which is grown on a germanium (Ce) substrate to achieve a similar type of memory sandwich. The device wherein the photoconductive layer and the heterojunction switch are combined differs in operation, in some particulars, from the FE/PC sandwich.

There is provided herein a device which is an improvement over the photoconductive layer heterojunction switch combination, in that it is substantially simpler than the latter combination. This device incorporates a suitable combination of the thickness of the ZnSe layer or other suitable photoconductive material (which is also suitable as a heterojunction switch), the wavelength of the incident light, and the voltage applied to the device. The simplification results from the fact that the upper part of the ZnSe layer can be caused to operate as the photoconductive layer, thereby eliminating the need for growing a second layer of a different compound.

The device shown in the figure is a sandwich structure consisting of a germanium substrate 2 upon which the ZnSe layer 4 having a thickness d...