Numerical Simulation of the Thermal Stress Field during Vertical Bridgman CdZnTe Single Crystal Growth

The thermal stress field of CdZnTe single crystals grown with the vertical Bridgman method was simulated with the thermal elastic finite-element model. The effects of the growth parameters, the furnace temperature gradient, the crucible descending velocity, and the thickness of the graphite film plating on the quartz crucible inner wall, on the thermal stress field were investigated. The stress at the crystal's edge is much larger than that at the crystal's center, and the stress at the crystal's bottom is larger than that at the crystal's top. The maximum stress 'sigma(max)' appears at the location where the crystal adhere equivalent to to the crucible's inner wall. When the furnace's temperature gradient was increased from 5 K/cm to 20 K/cm, the stress in the crystal increased a great deal. If no graphite film was plated on the crucible's inner wall, the stress at the crystal's 1 edge increased several times while the stress at the crystal's center increased only a little. On the contrary, when the thickness of the graphite film was increased from 250 mu m to 500 mu m, up to a pure graphite crucible, the stress at the crystal's edge decreased a little, while the stress at the crystal's center decreased a lot. In the range of the 0.5 similar to 3 mm/h, the crucible's descending velocity had little effect on the stress.