Development of Gallium Arsenide for Infrared Windows.
Final rept. 21 Jan 74-21 Feb 75,
TEXAS INSTRUMENTS INC DALLAS EQUIPMENT GROUP
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This report describes methods for preparing high quality infrared transmitting gallium arsenide. The work is broadly divided into categories describing doping studies, vertical pulling techniques, liquid encapsulation, growth methods, horizontal Bridgman and gradient freeze techniques, boat materials, and measurement results. In addition to infrared transmission curves, data are also presented which describe other physical parameters such as Knoop hardness and refractive index. A complete fabricating process is described which has routinely produced gallium arsenide infrared transmitting windows measuring 4 by 6 by 0.5 inches and exhibiting good transmission characteristics over the range of wavelength between 2 and 12 micrometers. The process is a horizontal synthesis technique in which high purity gallium, arsenic, and suitable dopants such as chromium and oxygen are compounded in a flat-bottom fused-silica boat. These are slowly cooled so that a directional freeze occurs at a predetermined rate. Annealing at elevated temperatures and slow cooling are a part of this process.
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