THERMODYNAMICS AND PHASE-EQUILIBRIA DATA IN THE S-GA-SB SYSTEM AUXILIARY TO THE GROWTH OF DOPED GASB SINGLE-CRYSTALS

An extensive survey of phase equilibria and thermodynamic data (Delta H, S, C-p, Delta G) on solid and liquid phases is presented for Ga-Sb, S-Ga and S-Sb subsystems which includes tables of the limiting activi ty coefficients. The construction method for chemical potential diagra ms has been applied in the form of log[a(Ga)/a(Sb)] versus log[P(S-2)/ bar] plots, the usefulness of which is discussed. The ternary phase di agram has been estimated. Using minimization of Gibbs energy the equil ibrium composition of coexisting phases in the S-Ga-Sb system has been evaluated regarding the determination of the maximum level of sulphur doping in GaSb single crystals grown by the Czochralski technique wit hout encapsulant. The calculated concentration of dissolved sulphur in GaSb solid was 10(16)-10(17) atoms per cm(3), which is in good agreem ent with the experimentally measured values of about 10(17) atoms per cm(3). After exceeding about 1.5 x 10(18) atoms per cm(3) in the melt, the second phase (Ga2S) started to separate spontaneously.