The diffusion of Si was carried out (900C, 5h, As pressure), from a 50nm sputtered film and into undoped semi-insulating material or Te-doped or Zn-doped liquid-encapsulated Czochralski material. Secondary ion mass spectroscopy and spreading resistance techniques were used to characterize the Si in-diffusion profiles. Lattice defects in highly Si-doped diffusion regions were studied as a function of the post-diffusion heat treatment (700C, 0.25h; 1000C, 0.5h) via the transmission electron microscopy of plan-view and cross-sectional samples. Two types of defect were observed in the diffused region. These were perfect prismatic loops of interstitial type on {110} planes, and Frank faulted loops on {111}; again of interstitial type. Defect formation, and the role of Si in defect generation, were explained in terms of a negative temperature dependence of the thermal equilibrium concentrations of VGa3-; which were assumed to mediate Si diffusion under highly n-doped conditions. Cathodoluminescence spectra at 4 and 77K were obtained from the diffusion layer. It was found that the Si diffusion affected the band-gap luminescence and generated 2 deep-level emission bands in the 0.9 to 1.3eV spectral region. It was suggested that these deep levels were associated with diffusion-induced defects and defect complexes.

Defects in GaAs after Si Indiffusion and Annealing: a TEM and CL Study. L.Herzog, U.Egger, O.Breitenstein, H.G.Hettwer: Materials Science and Engineering B, 1995, 30[1], 43-53