International Business Machines Corporation

Masanori Murakami

William H Price

Jerry M Woodall

Steven Lorenz Wright

Sandip Tiwari

Thomas N Jackson

Hung-Chang W Huang

Charles J Kircher

The control of barriers to carrier flow in a contact between a metal and a higher band gap semiconductor employing an intermediate lower band gap semiconductor with doping and greater than 1.5% lattice mismatch. A WSi metal contact of doped InAs on GaAs of 7.times.10.sup.-6 ohm/cm.sup.2 is provided.

Method for forming distributed barrier compound semiconductor contacts

In a semiconductor device, a contact with low resistance to a III-V compound semiconductor substrate was fabricated using refractory materials and small amounts of indium as the contact material. The contact material was formed by depositing Mo, Ge and W with small amounts of In onto doped GaAs wafers. The contact resistance less than 1.0 ohm millimeter was obtained after annealing at 800.degree. C. and the resistance did not increase after subsequent prolonged annealing at 400.degree. C.

Thermally stable low resistance contact

A thermally stable low resistance ohmic contact to gallium arsenide is fabricated using a layer of refractory material, and a layer of indium and a metal which forms thermally stable intermetallic compounds or single solid phase with indium. In forming the contact, a layer of indium is sandwiched between two layers of nickel, the sandwiched array of layers sitting on the substrate with the refractory tungsten layer on top to form a stratified structure. The stratified structure is heated to form nickel and indium intermetallic compounds and InGaAs layer at the metal/semiconductor interface. A thin layer of nickel between the indium and the gallium arsenide tends to form intermetallic compounds and limit a rate of diffusion of the indium into the gallium arsenide during heating so as to form a uniform fine distribution of InGaAs layer at the metal/gallium arsenide interface which results in low contact resistance. A contact resistance of 0.3 ohm-millimeters is obtained at elevated temperature in the range of 700.degree.-1200.degree. C. The resistance is stable after annealing at 400.degree. C. for 100 hours.

Thermally stable ohmic contact for gallium-arsenide

Thin film electrodes particularly suited for Josephson devices of improved thermal cyclability are prepared by depositing thin films of superconductive metal and an intermetallic compound former on a substrate held at a temperature below about 100.degree. K. and at a pressure below about 1.times.10.sup.-7 Torr so that intermetallic compound formation occurs at the grain boundaries of the metal to inhibit grain growth. The thin film electrodes are characterized by median grain size &lt;100 nm.

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Goldens Bridge, NY, United States of America

Masanori Murakami