PHASE-RELATIONS AND POINT-DEFECT EQUILIBRIA IN GAAS CRYSTAL-GROWTH

Thermodynamic phase relations in the binary system Ga-As are summarized and plotted in temperature-chemical potential diagrams. The phase extent of solid Ga1-xAsx(c) is evaluated by considering complete and partial equilibria of charged and uncharged vacancies, interstitials and antisite defects. The energy of formation of neutral Schottky defects has been chosen 4.0 eV, of a pair of neutral antisite defects 3.7 eV, of neutral Ga Frenkel defects 4.2 eV and of neutral As Frenkel defects 3.9 eV to fit the available experimental information. The formation of defect complexes such as the As-interstitial-antisite or As-interstitial-Ga- vacancy pairs requires about 2.2 eV binding energy to go to completion at a freeze-in temperature of 1100 K. Defect reactions in cooling or annealing processes after crystal growth are discussed and shown to be quite different for crystals with high or low dislocation density. © 1990.