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A New Thermally Stable Low Resistance Ohmic Contact to N-Type GAAS

IP.com Disclosure Number: IPCOM000121842D
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 1 page(s) / 41K

Publishing Venue

IBM

Related People

Aboelfotoh, MO: AUTHOR [+2]

Abstract

Disclosed is a new thermally stable low resistivity copper-germanium Cu3Ge ohmic contact to n-type GaAs. Prior art teaches the use of ohmic contacts to n-type GaAs based on the eutectic Au-Ge composition in conjunction with Ni. However, these contacts are generally thermally unstable when heated to 400oC. Another ohmic contact incorporating a thin layer of Au in conjunction with NiGeW metallurgy has been demonstrated in the prior art. However, the annealing temperature required to achieve a low contact resistance falls within a narrow temperature range, making this layered structure undesirable from a manufacturing view point. In addition, this layered structure exhibits a high sheet resistance. The disclosed material is formed at a temperature in a range extending from 200 to 400oC, and it is structurally simple.

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A New Thermally Stable Low Resistance Ohmic Contact to N-Type GAAS

      Disclosed is a new thermally stable low resistivity
copper-germanium Cu3Ge ohmic contact to n-type GaAs. Prior art
teaches the use of ohmic contacts to n-type GaAs based on the
eutectic Au-Ge composition in conjunction with Ni. However, these
contacts are generally thermally unstable when heated to 400oC.
Another ohmic contact incorporating a thin layer of Au in conjunction
with NiGeW metallurgy has been demonstrated in the prior art.
However, the annealing temperature required to achieve a low contact
resistance falls within a narrow temperature range, making this
layered structure undesirable from a manufacturing view point. In
addition, this layered structure exhibits a high sheet resistance.
The disclosed material is formed at a temperature in a range
extending from 200 to 400oC, and it is structurally simple.

      According to the present disclosure, ohmic contacts to n-type
GaAs are formed by first depositing a film of Ge with a thickness on
the order of 78 nm, followed by a film of Cu with a thickness on
the order of 122 nm.  The GaAs substrate is then heated at a
temperature in the range of 200 to 400oC for a period of 30 minutes
to form the compound Cu3Ge. The contact resistance as measured by the
transmission line method is found to be much less than 1 L mm and the
sheet resistance of the compound to be 0.8 L/[]. The advantage of the
Cu3Ge compound over the prior art is that, in ad...