A low power zone-refining system for semiconductor materials

Graduation date: 1964This paper presents an investigation of the power needs and\ud impedance-matching techniques involved when heating small charges of\ud relatively high-resistivity semiconductor materials. Topics of discussion\ud also include a brief section on the theoretical basis for\ud zone refining, relative merits of resistance and induction heating,\ud travel mechanism requirements, and work coil design.\ud Considerable emphasis is placed on the efficiency of coupling\ud between the induction heater and the load. Different methods of\ud coupling the power into loads of silicon and germanium are indicated.\ud The discussion on coupling centers around two work coil designs, a\ud single-turn coil and impedance-matching transformer, and a five-turn\ud coil, which is connected in series with the tank-circuit coil.\ud An induction heater capable of delivering 4 kw output power was\ud found sufficient for melting a zone 2 cm long in a 1.5 cm diameter\ud ingot. The system developed is capable of zone refining, zone leveling,\ud or crystal growing with either silicon or germanium