Development of 4-inch diameter InP single crystal with low dislocation density using VCZ method

Low dislocation density InP single crystals of 4-inch diameter have been successfully developed by the VCZ (Vapor pressure controlled Czochralski) method. The dopant used was Fe. The full length of the ingots was about 160 mm. In realizing a large size diameter InP crystal with low dislocation density, we used the VCZ method and a multi-zone heater method. The former can realize a low temperature gradient, which can suppress thermal stress during crystal growth and can reduce dislocation density. The latter can control a solid-liquid interface during growth. The optimized solid-liquid interface can reduce to be polycrystal. The EPD (Etch Pit Density) across the ingot was in the range of 1.7~0.4×10⁴ cm^-2, which is about half to one quarter of that of 3-inch diameter crystals grown by the conventional LEC method. The resistivity of the 4-inch crystal was more than 10⁷ Ω·cm across the whole ingot and the impurity level of the crystal is the same as that of the conventional LEC crystals. These findings demonstrate that the VCZ method is a promising technology for InP crystals not only to reduce dislocation density, but also to enlarge crystal diameter