Spatial distributions of impurities and defects in Te- and Si-doped GaAs grown in a reduced gravity environment

The spatial distributions of impurities and structural defects of Te- and Si-doped GaAs grown in space have been investigated using capacitance-voltage ( C-V ) method and scanning photoluminescence (SPL) and cathodoluminescence image (CLI) techniques. The deep center profile and free carrier concentration profile both along the crystal growth direction and across the wafer are measured and discussed in terms of the impurity segregation and the reaction between shallow donors and Ga and As vacancies during the space crystal growth. Dislocation density and its features throughout the space grown crystals are reported. Fine impurity striations in parallel with the space crystal surface are observed and are believed to be related to the well-known Marangoni convection resulting from surface tension gradients. A tentative structural model for the identification of the 1.0 eV PL band is postulated on the basis of the new experimental data presented in this paper.