Browse Prior Art Database

Light to Voltage Converter

IP.com Disclosure Number: IPCOM000094238D
Original Publication Date: 1966-Jul-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Agusta, BA: AUTHOR

Abstract

This light to voltage converter has an abrupt Ge-GaAs P-N heterojunction which, when operated at 78 degrees K or below, acts as a peak intensity light clipper.

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Light to Voltage Converter

This light to voltage converter has an abrupt Ge-GaAs P-N heterojunction which, when operated at 78 degrees K or below, acts as a peak intensity light clipper.

The energy-band diagram of the heterojunction indicates a notch or spike configuration 10. For the Ge-GaAs P-N or N-P semiconductor diode 12, the photocurrent that results from incident light 14 with energy between 0.66eV and
1.35eV on the GaAs side of diode 12 is similar to that of a P-N homojunction, excepting that it has reduced quantum efficiency. Essentially, the photocurrent is limited by the rate at which electrons can be thermally excited from the notch into the GaAs. However, at lower temperatures this thermal contribution to current is decreased and becomes negligible at 78 degrees K. When diode 12 is forward biased and maintained at 78 degrees K or less, the space charge resulting from the presence of optically excited electrons in the notch, changes the potential profile in such a way so as to reduce the forward current. For sufficiently high light intensity the forward current is reduced to zero. It is this characteristic that gives the peak clipping action of this device for light with energy between the band gaps of the two materials of diode 12.

Although with a diode of these semiconductor materials the clipper device can only operate effectively at 78 degrees K or below, it is theoretically possible to find two semiconductors that give a larger notch such that th...