Reduction of dislocation densities in InP single crystals by the LEC method using thermal baffles

Abstract

We have developed a modified liquid encapsulated Czochralski (LEC) method with thermal baffles, by which low dislocation density InP crystals can be grown. In this method, thermal baffles are set on top of the crucible in order to suppress the gas convection and thus to improve the temperature gradient in the LEC furnace. However, the dislocation densities depend not only on the temperature gradient but also on other growth conditions, such as crystal/crucible rotation rates, cooling rates, and the thickness of the pBN crucible. Since the rotation rate affects the solid/liquid interface shape, it is an important factor for the reduction of dislocation densities. By optimizing these conditions, for Sn and Fe doped InP crystals, average dislocation densities less than 5 x 10³ cm⁻² can be achieved. Dislocation free (DF) S and Zn doped InP crystals can also be grown if the carrier concentration is more than 3 x 1018 cm⁻³. The DF crystals become rectangular in shape.