Improvement of crystalline quality of 3-inch InP wafers

The process to decrease the dislocation density in 3-inch Fe-doped InP wafe rs is described. The crystal growth process is a conventional liquid encaps ulated Czochralsky (LEC) but thermal shields have been added in order to de crease the thermal gradient in the growing crystal, The shape, of these shi elds has been optimized with the help of numerical simulations of heat tran sfer 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 i mprovements on the dislocation densities have been investigated by etch pit s density (EPD) and X-ray diffraction (XRD) mapping: the dislocation densit y has dramatically decreased especially in the upper part of the crystal (f rom 70,000 to 40,000 cm(-2)), therefore matching the specifications for mic roelectronics applications. A same improvement has been obtained for S-dope d 3-inch wafers.