Diffusion Mechanism of Zn in GaAs and GaP Based on Isoconcentration Diffusion Experiments

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Abstract
Precise relationships between the diffusion coefficient D and the zinc concentration C are obtained from isoconcentration diffusion experiments performed at 900°C for zinc in GaAs and at 1000°C for zinc in GaP. It is found that D varies with C from a slightly less than cubic to a somewhat less than square dependence over the concentration range 1018 to 1020 cm−3. Possible mechanisms that result in concentration‐dependent diffusion are discussed. Under the conditions given above, it is concluded that diffusion occurs by an interstitial‐substitutional mechanism with the interstitial mode being dominant. The charge states of the various species involved in the diffusion are believed to be: (1) interstitial zinc atoms are doubly ionized donors; (2) substitutional zinc atoms are either neutral or singly ionized acceptors; and (3) gallium vacancies are neutral. A theoretical expression for D versus C, derived under these assumptions, fits the isoconcentration diffusion data over wide ranges of D and C through the use of only one adjustable parameter.

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