Author:
Kavanagh L.,Magee Charles W.
Abstract
The diffusion of Ge in semi-insulating GaAs was investigated for annealing temperatures in the range 650–800 °C. The samples consisted of electron-beam or metalorganic chemical-vapour deposition deposited Ge–GaAs interfaces encapsulated with SiO2. Ge diffusion profiles, measured with secondary-ion mass spectroscopy (SIMS), had a characteristic plateau and steep slope at the diffusion front, similar to those obtained for Si and Sn diffusion at SiO2-encapsulated GaAs. A saturated-surface concentration of 2 × 1019 atoms∙cm−3 was observed for anneals above 750 °C, likely the solid solubility of Ge in GaAs at these temperatures. Based on the Greiner–Gibbons substitutional-pair diffusion model (Appl. Phys. Lett. 44, 750 (1984)), the Ge-pair diffusion coefficients were calculated from the SIMS data. They ranged from 1 × 10−13 to 3 × 10−12 cm2∙s−1 but varied depending upon the annealing time and sample structure. A new model that eliminates the necessity for paired-Ge diffusion was introduced. It proposed that dissociation and out-diffusion of GaAs into the SiO2 produced a nonequilibrium flux of vacancies into the GaAs. Calculated profiles using a position-dependent Ge diffusion coefficient were shown to fit the SIMS data independent of the type of Ge diffusing species, whether single ions or pairs.
Publisher
Canadian Science Publishing
Subject
General Physics and Astronomy
Cited by
7 articles.
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