Why does slow crystal growth give larger crystals?

The simplistic explanation you were given is qualitatively correct. There are two key concepts here: Crystal Quality and also Crystal Size. Just about any crystal grown will have some sort of defects that affect the crystal quality. read more

Not only do they grow silicon as a single crystal, but they can also grow the crystals virtually defect free! The ability to grow these crystals is one of the main reasons that we are able to have the computing power we have today. read more

Crystal growth is highly temperature dependent, so increasing the temperature should increase the growth rate. But this also increases the nucleation rate of new crystals which could be good or bad, depending on what you want. read more