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Preparation of High Resistivity Semiconductors by Sputtering

IP.com Disclosure Number: IPCOM000076174D
Original Publication Date: 1972-Jan-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

It would be very desirable to obtain a semiconductor whose band gap lies in the visible, in both a highly conductive n- and p-type condition. There are two types of defects which can convert an n-type semiconductor such as CdSe into a p-type semiconductor. Impurities e.g., Cu substituting for Cd or N substituting for Se can behave as acceptors. Excess selenium atoms - cadmium vacancies or selenium interstitials, can act as acceptors. No combination of saturating a sample of cadmium selenide with both selenium and an acceptor impurity has yielded p-type cadmium selenide. We now find that cadmium selenide can be supersaturated with nitrogen, an acceptor which would be expected to be the most readily ionized and the most effective impurity.

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Preparation of High Resistivity Semiconductors by Sputtering

It would be very desirable to obtain a semiconductor whose band gap lies in the visible, in both a highly conductive n- and p-type condition. There are two types of defects which can convert an n-type semiconductor such as CdSe into a p-type semiconductor. Impurities e.g., Cu substituting for Cd or N substituting for Se can behave as acceptors. Excess selenium atoms - cadmium vacancies or selenium interstitials, can act as acceptors. No combination of saturating a sample of cadmium selenide with both selenium and an acceptor impurity has yielded p-type cadmium selenide. We now find that cadmium selenide can be supersaturated with nitrogen, an acceptor which would be expected to be the most readily ionized and the most effective impurity. The nitrogen does indeed behave as an acceptor, but the selenium pressure during growth was such that there was an excess of cadmium over selenium for this degree of doping. The resultant films were thus weakly n-type. This is a technique for raising the resistance of n-type CdSe films. It is suggested that with an accessible selenium pressure during or possibly after growth the films will become p-type. Sputtering in nitrogen gas produced highly oriented films even though the substrate was amorphous. This is contrasted to the polycrystalline results obtained when the sample is prepared in argon.

Procedure. CdSe was rf sputtered from a pressed stoichiometric cathode at ...