The Diffusion of Sb into Ge without Contamination by Fast Diffusing Electrically Active Impurities

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A method has been developed to permit the diffusion of Sb into Ge at high temperatures (850 C) without contamination by fast diffusing electrically active impurities in particular by Cu. A liquid metal alloy is used as a getter of Cu and other fast diffusing impurities. This alloy, Ga- In eutectic, completely encloses the Ge sample although in physical contact on only one face. The behaviour of Cu as a contaminant in Ge and the methods known to prevent and extract (or gather) Cu contamination are reviewed briefly. Preliminary experiments are described which demonstrate the difficulty of removing fast diffusing impurities in spite of the use of liquid metal getter (Ge-In and Au). The advantages and disadvantages of the technique are discussed.