Heat treatment method of znte single crystal substrate and znte single crystal substrate

Abstract

The present invention is to provide a heat treatment method for effectively eliminating Te deposits in a ZnTe single crystal substrate, and a ZnTe single crystal substrate having an optical characteristic suitable for use of a light modulation element and having a thickness of 1 mm or more. A heat treatment method of a ZnTe single crystal substrate, includes: a first step of increasing a temperature the ZnTe single crystal substrate to a first heat treatment temperature T 1 , and retaining the temperature of the substrate for a predetermined time; and a second step of gradually reducing the temperature of the substrate from the first heat treatment temperature T 1 to a second heat treatment temperature T 2 lower than the heat treatment temperature T 1 with a predetermined rate, wherein the first heat treatment temperature T 1 is set in a range of 700° C.≦T 1 ≦1250° C. and the second heat treatment temperature T 2 is set in a range of T 2 ≦T 1 −50.

1 . A ZnTe single crystal substrate for a light modulation element, wherein:
 when the substrate has a thickness of 1 mm or more, deposits included in a crystal have sizes of 2 μm or less and have densities of lower than 200 cm −3 , and   the ZnTe single crystal substrate has a light transmission of 50% or more to light beam having a wavelength of 700 nm to 1500 nm.   
     
     
         2 . A ZnTe single crystal substrate for a light modulation element, wherein:
 when the substrate has a thickness of 1 mm or more, deposits included in a crystal have sizes of 2 μm or less and have densities of lower than 200 cm −3 , and   the ZnTe single crystal substrate has a light transmission of 60% or more to light beam having a wavelength of 900 nm to 1500 nm.