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Heterojunction Ohmic Contacts to Si Using Ge/Si n+/n+ Structures

  • M. J. Hafich (a1), R. L. Gillenwater (a1), G. Y. Robinson (a1) and P. Sheldon (a2)

Abstract

Ohmic contacts to n-type Si have been formed using a thin n layer of Ge grown by selective-area molecular beam epitaxy. The n+Ge is used to lower the metal-semiconductor barrier energy and thus reduce the contact resistivity of the thin film structure. Al/n+Ge/n+Si test devices were fabricated in a manner compatible with conventional VLSI processing and consisted of a 3500 A thick layer of arsenic-doped Ge grown at 250°C on a selectively diffused, phosphorus-doped Si substrate. Using both four terminal Kelvin and transmission line devices, unsintered Al/Ge/Si structures exhibited contact resistivities a factor of five lower than Al/Si control devices, in agreement with theoretical calculations based on a simple tunneling model for the metal/Ge/Si heterojunction ohmic contact.

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Heterojunction Ohmic Contacts to Si Using Ge/Si n+/n+ Structures

  • M. J. Hafich (a1), R. L. Gillenwater (a1), G. Y. Robinson (a1) and P. Sheldon (a2)

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