It is suitable for growing semi-conductively alloys like gallium arsenide. A typical arrangement is furnished with an induction heater that provides a controllable temperature gradient along the furnace. The boar with the material is placed in sealed tube and moved from high temperature zone to low temperature zone. The chemical purified gallium arsenide material is melted at about 1250 degree centigrade in high temperature zone and slowly passes into lower temperature zone where it solidified from one end to about 620 degree centigrade. The temperature is chosen so that a small amount of arsenide always kept in this zone will provide an arsenic atmosphere in which crystallisation of gallium arsenide occurs.