High speed crystal growth and solidification using laser heating

High speed melting and freezing phenomena are reviewed with emphasis on silicon crystal growth. Laser heating has been particularly advantageous for the exploration of such velocity regimes. New transient probe techniques have been developed to investigate interface motion. The solid-phase epitaxial growth of amorphous Si overlayers is first discussed. Silicon liquid-phase epitaxy and enhanced dopant segregation effects up to velocities of 15 m/s are reviewed. Amorphous Si is formed from the melt at velocities greater than 15 m/s. The melting of amorphous Si can produce explosive crystallization. It has been discovered that amorphous Si melts in a first order phase transition at a temperature 250°C lower than the crystal melting temperature. The velocity-undercooling relationships for Si are being constructed from these measurements. Applications of strip heaters for Si crystal growth on SiO ₂ will be discussed. Very rapid laser heating techniques are now being applied to metals to measure solidification velocities and phase transformations.