| 摘要 |
784,431. Semi-conductor devices. PHILIPS ELECTRICAL INDUSTRIES, Ltd. March 31, 1955 [April 1, 1954], No. 9425/55. Class 37. Apparatus for manufacturing semi-conductive bodies having p-n junctions comprises a tubular container 1 having a contraction 2 terminating in a bulb 3 which contains sulphur 4, the main charge 5 of lead sulphide being contained in a vessel 6 of sintered aluminium oxide. The container 1 is exhausted and the part containing vessel 6 is heated to 500‹ C. by a carbon furnace 9 and the sulphur 4 is heated to a temperature of 444‹ C. by an electric oven 8 to produce a sulphur vapour pressure of 1 atm. in the whole of the container. The temperature of the lead sulphide 5 is increased to 1150‹ C. by a high-frequency coil 7 which is moved from left to right at a speed of 1 mm. per minute. The lead sulphide solidifying at the edge of the melting zone exhibits p conductivity since sulphur is included in the lattice at a concentration higher than that corresponding to the stoichiometric lead sulphide. After the molten zone has traversed about half of the charge the coil is stopped and the oven 8 cooled to a temperature of 400‹ C., the vapour pressure of the sulphur thus being decreased to 0.4 atm. and the coil 7 is set in movement again. Lead sulphide of n-type conductivity now solidifies at the edge of the melting zone due to the sulphur pressure of 0.4 atm. being in equilibrium with a melt containing a smaller amount of sulphur than corresponds to the stoichiometric lead sulphide. After cooling, the charge 5 in the form of a rod is removed. Instead of the materials previously described a quantity of cadmium is placed in bulb 3 and a vessel 6 of graphite contains cadmium telluride and indium is added to the left-hand side of the charge to an amount such that, when a zone 2 cms, wide is provided by melting an indium concentration of 10<SP>19</SP> atoms per c.c. is obtained. After being exhausted, vessel 1 is heated to 900 ‹ C. by oven 9 and bulb 3 is heated to 750‹ C. by oven 8 to produce a cadmium vapour pressure of 1 atm. in the whole vessel. A zone of the charge is then melted at 1040‹ C. by coil 7 which is moved from left to right at 5 mms. per minute and after half of the charge has been traversed, the temperature of the cadmium in bulb 3 is reduced to 650‹ C. to lower the cadmium vapour pressure to 0.3 atm. The part of the charge which solidifies at a pressure of 1 atm. is n-conductive and the remainder solidifying at 0.3 atm. pressure is p-conductive. In a still further embodiment a charge of lead sulphide containing 0.5 per cent of silver is heated in a sealed vessel by a moving coil, the vessel having inlet and outlet connections for a gas flow of H 2 S to provide a p-type material and a mixture of H 2 and H 2 S to provide n-type material. |
