CONCENTRATION-DEPENDENT AND INDEPENDENT SI DIFFUSION IN ION-IMPLANTEDGAAS

The diffusion of silicon has been studied in [100] GaAs implanted with 1x10(16) 40-keV Si-30(+) ions/cm(2). The Si concentration profiles we re measured by secondary-ion mass spectrometry and nuclear resonance b roadening techniques and the defect distributions by the Rutherford ba ckscattering spectrometry channeling technique. The implanted samples were subjected to annealing in argon atmosphere in the temperature ran ge 650 degrees C-850 degrees C. Two independent silicon diffusion mech anisms were observed. Concentration independent diffusion, observed as a broadening of the initial implanted distribution, is very slow and is assigned to Si atoms diffusing interstitially. Concentration depend ent diffusion with low solubility and extending deep into the sample i s quantitatively explained by diffusion via vacancies of Si atoms in t he Ga and As sublattices. Diffusion coefficients together with carrier concentration as a function of Si concentration are given at differen t temperatures. The solid solubility of Si in GaAs has been determined and an exponential temperature dependence observed. An estimate of th e amount of Si atoms residing on either Ga or As sites and the amount of Si-Ga(+)-Si-As(-) pairs is given. Finally, a fast method is present ed for solving the diffusion equation numerically.