High quality InP substrates grown by the VCZ method

We have successfully developed 220 mm-long 2-inch diameter crystals doped with S and 200 mm-long 3-inch diameter crystals doped with S or Fe by the VCZ method. Temperature gradients above the InP melt and in the melt were controlled by multi-zone heater to suppress the twin formation during the crystal growth. The low EPD area (EPD⩽500 cm^-2) of S-doped wafers could be more than 13 cm² for 2-inch diameter crystal and 22 cm² for 3-inch diameter crystal throughout the ingot. The average EPD of 3-inch diameter wafers doped with Fe could be reduced to lower than 7×10³ cm ^-2. The residual strains detected by infrared polarization microscope and quantitative photoelastic characterization could be reduced by the VCZ method. The results of double crystal x-ray diffraction measurement also indicate the improvement of crystal perfection of the crystal grown by the VCZ method