Search

The intermixing of AlAs-GaAs superlattices has been investigated as a function of Si concentration following anneals in the range of 500 to 900 °C. The superlattice samples were grown by molecular beam epitaxy and the near surface layers were doped with silicon at concentrations of 2×1017 to 5×1018 cm-3. Si and Al depth profiles were measured with secondary ion mass spectrometry (SIMS). The diffusion length and activation energy of Al as a function of silicon dopant concentration were derived from the SIMS data. In the temperature range studied a single activation energy for the Al diffusion of ∼4 eV was observed, and the Al diffusion coefficients increased rapidly with Si concentration. [ABSTRACT FROM AUTHOR]

The effects of Si ion implantation and annealing on AlAs-GaAs superlattices are examined with secondary ion mass spectrometry (SIMS), Rutherford backscattering spectrometry (RBS), and transmission electron microscopy (TEM). Samples implanted with 180 keV 28Si+ of doses ranging from 3×1013 to 3×1015 cm-2 are examined before and after a 3-h 850 °C anneal. Both the TEM and RBS channeling data indicate the formation of a heavily damaged surface layer where diffusion of Al is inhibited even after thermal annealing. After annealing, however, significant mixing is observed at depths well beyond the implant range. Depth-dependent diffusion lengths of Al and Si are derived from the SIMS data. The diffusion coefficient of Si is markedly reduced in the unmixed regions with both the Si and Al concentrations exhibiting abrupt forward and rear diffusion fronts. [ABSTRACT FROM AUTHOR]

Silicon implantation induced mixing of a 400-Å period AlAs/GaAs superlattice grown by organometallic chemical vapor deposition is examined using secondary ion mass spectrometry and transmission electron microscopy. The depth dependence of Al and Si diffusion for a 180-kV 3×1015 cm-2 Si+ implant is measured as a function of implantation temperature, annealing temperature, and annealing time. The room-temperature implanted sample exhibits a near-surface mixing inhibition following anneal. No mixing inhibition is observed in samples implanted at higher temperatures. Si segregates rapidly into the GaAs layers during the anneal. Si diffusion is inhibited near the peak of the implant. Mixing depths and defect distributions are strongly dependent on the processing conditions employed. The results are consistent with a divacancy model for Al diffusion. [ABSTRACT FROM AUTHOR]