The system Ga–As–Sn: Incorporation of Sn into GaAs

Abstract

Liquidus isotherms have been determined experimentally and computed with a ``simple solution'' model for the Ga–As–Sn system. Electrical properties of the Sn-doped GaAs crystals grown from the equilibrium liquidus were determined and several incorporation mechanisms inferred. Tin is taken to incorporate primarily as the donor SnGa, and also to a lesser extent as a deep acceptor SnAs·mVGa, with m probably 2. At the temperatures and growth rates used in this work the incorporation of Sn from the liquid phase into the solid is controlled by equilibrium between the liquid and the crystal surface. The incorporation is therefore influenced by the position of the Fermi level at the growing solid surface rather than in the bulk of the crystal. Subsequently, the donors and acceptors associate extensively to form neutral species so that the total Sn in the crystals is much greater than ND +NA.