Process of Preparing a p-n Junction in Semi-Conductor Alloys of Mercury Telluride and Cadmium Telluride

摘要

1,191,171. Semi-conductor devices. CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE. 26 May, 1967 [27 May, 1966], No. 24711/67. Heading H1K. A method of producing a PN junction in a body of semi-conductor material having the composition Hg 1-x Cd x Te, 0#x#0À4, comprises subjecting a monocrystalline body to a number of thermal treatments of durations t, at temperatures T in the presence of mercury vapour at pressures P, wherein for the first treatment t 1 increases as a function of the thickness of the body, T 1 350‹ C., and P 1 is from 6 Î 10SP-3/SP to 1À5 Î 10SP-2/SP atmospheres, to produce an N-type body having a low concentration of charge carriers and then either (i) performing a second treatment in which t 2 is from 1 to 30 min., T 2 300‹ C. and P 2 is from 0À2 to 1 atmosphere to produce a P-type body having a high concentration of charge carriers, followed by a third treatment in which t 3 is from 1 to 3 hours, T 3 is from 300‹ to 500‹ C. and is less than or equal to T 2 , and P 3 equals the equilibrium pressure of mercury vapour at the temperature T 3 , to produce an N-type surface layer on the body; or (ii) omitting the second treatment and performing the third treatment only as in (i) to convert the body to P-type while maintaining a surface layer of N-type conductivity. The body may then be cut to the required size and the surface treated first in a solution containing fuming hydrochloric acid, nitric acid and a trace of fuming nitric acid, followed by rinsing by diluting the solution with absolute ethyl alcohol and then using a solution comprising a mixture of absolute ethyl alcohol and bromine, followed by a second rinsing. Contacts are provided by electrolytically depositing layers of gold on the P- and N-type regions and welding indium or indium-silver to the layers to produce a photo-voltaic device. The electrodes on either region may also be of platinum, and that on the N-type region may additionally be of indium or of gallium-indium or mercury-indium eutectics. The electrodes may also be produced by evaporation. The device may be utilized in photo-conductive, photomagneto-electric, and photovoltaic detectors, for light emissive and laser devices, and for modulators and amplifiers using piezoabsorption, piezo-reflectivity, photo-absorption, photo-reflectivity or the Franz-Keldysh effect (i.e. variation of the activation energy #E by the application of an intense electric field).