The process to decrease the dislocation density in 3-inch Fe-doped InP wafers is described. The crystal growth process is a conventional liquid encapsulated Czochralsky (LEC) but thermal shields have been added in order to decrease the thermal gradient in the growing crystal. The shape of these shields has been optimized with the help of numerical simulations of heat transfer and thermomechanical stresses.

This process has been performed step by step with a continuous feedback between calculations and experiments. A 50% reduction of the thermal stress has been obtained. The effects of these improvements on the dislocation densities have been investigated by etch pits density (EPD) and X-ray diffraction (XRD) mapping: the dislocation density has dramatically decreased especially in the upper part of the crystal (from 70,000 to 40,000 cm-2), therefore matching the specifications for microelectronics applications. A same improvement has been obtained for S-doped 3-inch wafers.

Source:IOPscience

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