Temperature gradient zone melting utilizing selective radiation coatings

Claim 1

An improvement in the processing of a body of semiconductor material by thermal gradient zone melting comprising the steps of: (a) selecting a body of semiconductor material having a preferred crystal structure, a preferred type of conductivity, a preferred level of resistivity, two major opposed surfaces being, respectively, the top and bottom surfaces of the body, at least one of the major surfaces having a preferred planar crystal orientation, and a vertical axis substantially aligned with a first preferred crystal axis of the material of the body; (b) forming a layer of a material suitable for absorbing a predetermined range of wavelength of the radiation spectrum impinging thereupon on at least one of the two major opposed surfaces, the layer having a predetermined thickness, expressed by the following general equation: ##EQU6## wherein n= any positive integer greater than zero λ = the wavelength of the most intense portion of radiation spectrum impinging upon the material in vacuum and N= the index of refraction of the material; (c) exposing the processed body to a source of radiant energy; (d) absorbing the predetermined range of wavelength of the most intense portion of the spectrum in the layer of material, and (e) increasing the heat flow lines through the material of the body to enhance the migration of a melt of metal-rich semiconductor through the body by thermal gradient zone melting.