Effect of Structural Defects in Germanium on the Diffusion and Acceptor Behavior of Copper

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Abstract
The effect of dislocations in Ge upon the diffusion of Cu has been studied using Ge crystals having different etch‐pit counts as well as on Ge specimens bent on a (112) axis. The percentage of the total Cu introduced in a given time which attains the acceptor state was measured by comparing conductivity to radioactivity determinations employing Cu64. In addition, the detailed diffusion processes have been studied as a function of time and etch‐pit density by means of autoradiographs taken both parallel and perpendicular to the direction of diffusion and also by delineation of p‐n boundaries. The two most important findings are: (1) the slow attainment of acceptor equilibrium especially in Ge having low concentrations of dislocations and (2) the identification of dislocations as the initial loci of acceptor copper in Ge. The results call for a revision of our ideas on the mechanism of diffusion of Cu. The view is advanced that Cu atoms enter Ge interstitially at a high rate (>10−4 cm2/sec), but that their flow and ultimate concentration is limited by the effective rate of generation and equilibrium concentration of vacancies chiefly at dislocations.

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