Dynamics analysis of twin formation for InP and preparation of 6 inch InP single crystals

Through the experiments of indium phosphide (InP) crystal growth, it was found that InP crystals with twin-free or low twinning probability can be grown repeatedly in the range of 0-90 degrees growth angles at a high temperature gradient and low growth rate. Based on the experimental phenomena, it is inferred that twin formation is mainly related to undercooling at the growth interface. A kinetic model for twin nucleation based on the morphologies of the triple junction (tri-junction) region has been proposed from the point of view of the nucleation kinetics of crystal growth. It is found that when the undercooling of facets exceeds a critical value, the probability of twin nucleation increases with the increase of undercooling. When the twin boundary energy is 0.5 mJ m-2, this critical value approaches 0.2 K. Based on this model, the comprehensive influence of interface morphologies, temperature gradients, and growth rates on twin nucleation was analyzed. In addition, the effects of temperature fluctuations, constitutional supercooling, impurities and dopants have also been well explained. By controlling the morphologies of the growth interface under low undercooling, InP single crystals with a diameter of 170 mm were prepared using a flat shoulder method. Twin-free InP crystals can be grown under suitable growth conditions. A kinetic model for twin nucleation is proposed.