Structural and electrical properties of n-type bulk gallium arsenide grown from non-stoichiometric melts

The pulling of Si-doped GaAs from melts either Ga- or As-rich resulted in crystals having substantially different properties. The crystals grown from As-rich melts exhibited higher electron mobility with respect to those grown under Ga-rich conditions. These higher mobilities have been ascribed to more pronounced incorporation of silicon in donor sites and to lower density of acceptor-like complexes involving Si. The Ga-rich crystals were characterized by a lower concentration of dislocations. Such dislocation reduction is explained in terms of reduction of point defects (As interstitials) which can generate microloops and subsequently dislocations. An extensive TEM investigation further supports the idea of Asi as the point defect which more largely influences the structural properties of LEC GaAs. It is shown that the concentration and size of microdefects is drastically reduced when pulling from Ga-rich melts.