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Low Resistivity Ohmic Contacts to N GaAs With Special Application to GaAs PN and Microwave Oscillator Devices

IP.com Disclosure Number: IPCOM000095063D
Original Publication Date: 1965-Sep-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Rupprecht, HS: AUTHOR [+2]

Abstract

The technique is for effecting low resistance contacts to the surface of an N-type gallium arsenide (GaAs) wafer. The surface of the N-type gallium arsenide (GaAs) wafer is initially coated with a liquid alloy mixture of gallium (Ga) and indium (In) which is doped with a suitable donor impurity, e.g., tellurium, selenium, tin, etc. The ratio of gallium to indium is chosen close to the eutectic composition (melting point 15 degrees C.).

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Low Resistivity Ohmic Contacts to N GaAs With Special Application to GaAs PN and Microwave Oscillator Devices

The technique is for effecting low resistance contacts to the surface of an N- type gallium arsenide (GaAs) wafer. The surface of the N-type gallium arsenide (GaAs) wafer is initially coated with a liquid alloy mixture of gallium (Ga) and indium (In) which is doped with a suitable donor impurity, e.g., tellurium, selenium, tin, etc. The ratio of gallium to indium is chosen close to the eutectic composition (melting point 15 degrees C.).

Thus, the liquid alloy mixture can be applied to the surface at 300 degrees K. The residue is cleaned off with an appropriate organic solvent and the wafer is fired at between 500 degrees C and 800 degrees C for three minutes in a forming gas atmosphere. This results in a surface layer providing low ohmic contact. This can be further protected by a thin metallic coating, for example, of palladium (Pd) formed by dipping the wafer into a solution of palladium chloride (PdCl(2)) and water (5 grams/ 100 cm) for a few seconds.

The thickness of the palladium (Pd) coating can be controlled by varying the temperature of the palladium chloride-water solution. Alternatively, the surface can be coated with successive layers of gold (Au), nickel (Ni), and gold (Au) for improved soldering capabilities.

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