Fine structures of residual strain distribution in Fe-Doped lnP-100) wafers grown by the LEC and VCZ methods

Abstract

By using a high-spatial-resolution scanning infrared polariscope, in-plane components of residual strain have been characterized quantitatively in 2′Φ wafers of Fe-doped InP( 100) single crystals grown by the liquid-encapsulated Czochralski (LEC) and the vapor pressure controlled Czochralski (VCZ) methods. The twodimensional distribution maps of LEC-grown wafers reveal characteristic fine structures such as slip-like patterns originated from crystallographic glides during the crystal growth process, highly strained spots and filaments due to inclusions or voids inside the wafer, or due to scratches on the surface. The sliplike patterns are seldom observed in the VCZ-grown wafers. The residual strain value averaged over the whole region of wafer is also examined, together with etch pit density and resistivity, as a function of the solidified fraction. It is found that the residual strain in the Fe-doped InP crystals grown by the LEC and VCZ methods mainly depends on the thermal stress during the growth process rather than on the impurity-hardening effect of Fe.Key words: InP, infrared polariscope, liquid-encapsulated Czochralski (LEC) method, residual strain, vapor pressure controlled Czochralski (VCZ) method