A study was made of monocrystalline and polycrystalline wafers which had been grown from stoichiometric and non-stoichiometric melts. In the case of crystals that had been grown from stoichiometric melts, the Ga/Sb ratio was slightly higher, and remained uniform throughout. At the grain boundaries of polycrystals, the Sb content was higher than in other regions. Crystals which were grown from Ga-rich or Sb-rich melts exhibited inclusions of the excess component. Post-growth annealing was carried out in vacuum or in Ga-rich atmospheres. Heat treatment in vacuum had very little effect upon the local composition. On the other hand, localized crystallization occurred at grain boundaries and inclusions, in the presence of excess Ga. It was shown that annealing in Ga ambients could produce defect-free wafers with a very homogeneous composition. It was concluded that excess Sb which was liberated from the crystal during growth remained at grain boundaries and other extended defects. Vacant Sb sites were suggested to be responsible for the formation of native acceptor centers such as VGa and GaSb.

P.S.Dutta, C.Marín, E.Diéguez, H.L.Bhat: Journal of Crystal Growth, 1996, 160[3-4], 207-10