Method for preparing high purity crystalline semiconductive materials in bulk

Abstract

Abstract GROUPS III-A-V-A AND II-B-VI-A COMPOUNDS AND ALLOYS THEREOF ARE PREPARED, FOR EXAMPLE, BY FLOWING A GASEOUS GROUP V COMPOUND INTO A BATH OF A MOLTEN GROUP III-A ELEMENT HAVING A TEMPERATRUE PROFILE ESTABLISHED THEREABOUT. A CONTAINER CONTAINING A MOLTEN METAL OR A MIXTURE OF SAID METALS IS PLACED IN A VERTICAL FURNACE, ABOUT WHICH A STEEP TEMPERATURE GRADIENT IS ESTABLISHED ALONG ITS LENGTH. A GASEOUS COMPOUND OF A GROUP V-A ELEMENT OR A MIXTURE OF GASEOUS GROUP V-A COMPOUNDS AND AN INERT GAS IS PERMITTED TO FLOW INTO THE MOLTEN GROUP III-A METAL. A TEMPERATURE GRADIENT ALONG THE LENGTH OF THE CRUCIBLE CAUSES THE GROUP V-A ELEMENT TO REACT WITH THE MOLTEN GROUP III-A METAL AND THE REACTION PRODUCT THEREFROM DISSOLVES IN THE MOLTEN METAL. THE LOWER SURFACE OF THE CRUCILBE IS COOLED BY A COOL AIR BLAST WHICH ESTABLISHES CONVECTION CURRENTS WITHIN THE MOLTEN METAL SO THAT AS THE SOLUBILIZED GROUP III-A-V-A COMPOUND MOVES DOWNWARDLY IN THE CRUCIBLE IT MIXES WITH THE MOLTEN GROUP III-A COMPOUND, IS COOLED AND CRYSTALLIZES OUT OF THE MOLTEN METAL AS A HIGHLY PURE CRYSTALLINE INGOT OF THE SPECIFIC III-A-V-A COMPOSITION. IT HAS ALSO BEEN FOUND THAT PURE SILICON CARBIDE CAN BE PREPARED IN A SIMILAR, MANNER. FOR EXAMPLE, A MIXTURE OF METHANE AND AND INERT GAS IS PERMITTED TO FLOW INTOMOLTEN SILICON WHICH IS SIMILARLY SUBJECTED TO A TEMPERATURE GRADIENT. THE MATERIALS FORMED BY THE PROCESS OF THIS INVENTION ARE FOUND TO BE OF VERY HIGH PURITY.

Inventors

• 👤 Thomas S Plaskett

Bibliographic Details