Dislocation elimination in THM growth of GaAs

Abstract

GaAs crystals 1 cm in diameter were grown by the Travelling Heater Method in [111] Ga,1̄1̄1̄[111] As, 〈110〉 and 〈211〉 orientations. Etch pit densities on cross-sectional slices of 〈111〉 crystals decreased exponentially with growth distance, while those on longitudinal slices of 〈110〉 and 〈211〉 crystals changed little with distance. Equations were derived for dislocation density versus distance for two elimination mechanisms. It was concluded that dislocations were probably eliminated by growing out to the surface due to their propagation approximately normal toa convex interface. Some mutual annihilation of dislocations may have occured in the first few millimeters of growth, but this does not seem to have been the predominant mechanism for elimination of dislocations. Rapid removal of the growth ampoule from a hot furnace caused axial dislocations to be generated in the portion of 〈111〉 cyrstals at temperature above about half of the melting point of GaAS.