Thermal Field of 6-inch Indium Phosphide Single Crystal Growth by Semi-sealed Czochralski Method

Indium phosphide (InP) is a kind of important compound semiconductor material, now increasingly used in high frequency electronic devices and infrared optoelectronic devices. Currently, the price of InP devices is much higher than that of GaAs devices, mainly because of its low yield of single crystals and increase of epitaxy, and device process cost due to smaller wafer diameter. Increasing the diameter of InP single crystals is critical to reducing wafer and semiconductor process costs. The main difficulties in preparing large diameter InP single crystals are increasing crystal yield and reducing stress in the crystal. The vertical gradient freeze (VGF) and the liquid encapsulated Czochralski (LEC) methods are commonly used in the industry to prepare InP, while the VGF method has little success in preparing 6-inch InP crystals, and the crystals prepared by the LEC method tend to have higher stress and dislocation density. Here we reported a semi-sealed Czochralski (SSC) method to grow large diameter InP crystals. Numerical simulations were used to analyze the temperature distribution in melt, crystal, boron oxide, and atmosphere in LEC and SSC method, with emphasis on temperature field of the SSC method. As a simulation result, the temperature gradient in the crystal of SSC method is 17.4 K/cm, significantly lower thanthat of 28.7 K/cm in the LEC method. And temperature of atmosphere near the crystal shoulder in the diameter control stage of the SSC method is 504 K higher than that of the LEC method. Then the used thermal field of SSC method was optimized according to the simulation results, and 6-inch (1 inch=2.54 cm) S doped InP single crystals with low defect density and no cracks were prepared by this optimized method, which confirmed that the optimized SSC method is promising for growing large-size InP single crystals.