Patent GB-990518-A (GB)
Title: Improvements in methods of producing an unsaturated vapour pressure of a substance in a space
IPC: H01L21/00
Filed: 1961-08-29
Abstract: <PICT:0990518/C1/1> A vapour of a substance, such as Cd, at a desired temperature, e.g. of 900 DEG  C. with a vapour pressure less than the saturated vapour pressure of the substance at the desired temperature but higher than the triple point pressure is produced and maintained, for use in the heat treatment of solid, preferably semiconductor materials, such as CdTe crystals containing 5 X 1016 atoms of Au/Cc. by heating a first space to the desired temperature, providing an amount of the substance in a second space communicating at its lower end with the first space and at its upper end with a third space containing a gas, such as nitrogen, at the desired unsaturated vapour pressure and heating the lower part and cooling the upper part of the second space so that in the lower part the substance entirely evaporates to condense in the upper part and flow back to the lower part in which it evaporates again, thus effecting circulation in the second space by reflux action. The first and second space may be together defined by a vertical tube 1, the lower closed end 2 of which is arranged in a furnace 3 and the wall of a portion 7 above the furnace is cooled by air blown through pipes 6, the upper portion 4 opening into a gas-filled container 5 being at the desired pressure 0.4 or 0.8 atmosphere. Other materials may be treated in other vapours, such as CdS in Cd or S vapour, for producing semi-conductor devices in photoelectric cells.  Also Si may be doped with P or Sb by diffusion from the vapour, and KCl crystals with excess K.ALSO:A vapour of a substance, such as Cd, at a desired temperature, e.g. of 900  DEG C. with a <PICT:0990518/C6-C7/1> vapour pressure less than the saturated vapour pressure of the substance at the desired temperature but higher than the triple point pressure is produced and maintained, for use in the heat treatment of solid, preferably semi-conductor materials, such as CdTe crystals containing 5 X 1016 atoms of Au/c.c., by heating a first space to the desired temperature, providing an amount of the substance in a second space communicating at its lower end with the first space and at its upper end with a third space containing a gas, such as nitrogen, at the desired unsaturated vapour pressure and heating the lower part and cooling the upper part of the second space so that in the lower part the substance entirely evaporates to condense in the upper part and flow back to the lower part in which it evaporates again, thus effecting circulation in the second space by reflux action. The first and second space may be together defined by a vertical tube 1, the lower closed end 2 of which is arranged in a furnace 3 and the wall of a portion 7 above the furnace is cooled by air blown through pipes 6, the upper portion 4 opening into a gas-filled container 5 being at the desired pressure 0.4 or 0.8 atmosphere.  Other materials may be treated in other vapours, such as CdS in Cd or S vapour, for producing semi-conductor devices in photo-electric cells.  Also Si may be doped with P or Sb by diffusion from the vapour, and KCl crystals with excess K.