Fermi-level dependent diffusion of ion-implanted arsenic in germanium.

The diffusion of arsenic has been studied in <100> Ge, implanted with 1·10[sup 15], 120-keV [sup 75] As[sup + ]ions/cm&sup 2;. The implanted samples were subjected to annealing in argon atmosphere in the temperature range of 450-550°C. The annealing times varied between 0.5 and 91 h. The As concentration profiles were measured by secondary ion mass spectrometry. A Fermi-level-dependent diffusion of As atoms was observed and quantitatively explained by diffusion via Ge vacancies with charge states 0 and 2-. The activation energies and pre-exponential factors for As diffusion through neutral Ge vacancies was found to be 3.4±0.3 eV and 2.02 x 10[sup 20] nm²/s, respectively, and through doubly negatively charged vacancies 2.9±0.3 eV and 1.89 x 10[sup 16] nm²/s, respectively. The solid solubility limit of As increases with temperature from about 1 x 10[sup 19] cm[sup -3] at 450°C to about 5 x 10[sup 19] cm[sup -3] at 550°C. [ABSTRACT FROM AUTHOR]