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Improvement of CdSe Photoconductor Properties

IP.com Disclosure Number: IPCOM000076593D
Original Publication Date: 1972-Mar-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Jacobs, JT: AUTHOR [+2]

Abstract

In order to read and write on ferroelectric photoconductive (FE/PC) chips, it is important that the PC have symmetrical properties in both polarities. This requires symmetrical dark resistivities, gains, light resistivities and decay times. These properties are dominated by the contacts. Recent-measurements indicate that the contact at the FE/PC interface produced a Schottky barrier which was much lower than the barrier at the CdSe-Au-Air interface. This lower barrier introduces a great deal of asymmetry into the PC operating characteristics.

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Improvement of CdSe Photoconductor Properties

In order to read and write on ferroelectric photoconductive (FE/PC) chips, it is important that the PC have symmetrical properties in both polarities. This requires symmetrical dark resistivities, gains, light resistivities and decay times. These properties are dominated by the contacts. Recent-measurements indicate that the contact at the FE/PC interface produced a Schottky barrier which was much lower than the barrier at the CdSe-Au-Air interface. This lower barrier introduces a great deal of asymmetry into the PC operating characteristics.

These asymmetries may be reduced by preparing the samples such that more symmetrical barriers are formed. One method is to introduce oxygen to the initial layer by the following process.

Gold coated PYREX* substrates are heated to 220 degrees C in a technical vacuum. Nitrogen is used to backfill the sputtering system to a pressure of 30mu.

A presputter period of 1/2 hour at 200w is used to purify the system of contaminants. The substrates are coated with a thin film of CdSe (500 Angstroms). The system is then backfilled with nitrogen to 0.5 torr. Air is flushed through the chamber for 10 minutes while the film is maintained at approx. = 220 degrees C. The system is then pumped down to less than 10/-6/torr and backfilled with nitrogen to 30mu. Another 300 minute presputter period follows. Then a thick film of CdSe (5000 Angstrom) is sputtered onto the substrates. The system is bac...