Ion-implanted evaporated germanium layers as n.sup.+ contacts to GaAs

摘要

A method of forming a single, reliable n.sup.+ contact for discrete GaAs devices. A film of p-type Ge is deposited uniformly over the surface of a n-type GaAs substrate. Ions of phosphorous or arsenic are implanted to 510.sup.18 ions/cc at a depth of 1500 A. The ends and the sides of the substrate and Ge layer are capped by a CVD oxide and annealed at 450-500 C. for about one hour. This process over- compensates the initial p-type layers which results in the Ge layer becoming n.sup.+. The oxide is removed by an etch process and the n.sup.+ Ge is etched to form two separate contact sections of n.sup.+ Ge. The n. sup.+ Ge is then metalized to form ohmic contacts by use of NiAu. A CVD oxide overcoat may again be applied and annealed at about 500 C. to drive a shallow 200-500 A, n.sup.+ germanium diffusion into the substrate.