Patent ID: 7825422

Claim:
A submount comprising: a flat-plate-shaped ceramic substrate having a placement surface, and an electrode, wherein the ceramic substrate comprises a substrate body having a gray-colored aluminum nitride sintered body with a thermal conductivity of 170 W/m·K or more, and a coat layer coating at least a part of a surface of the substrate body, the coat layer being a white ceramic different from the aluminum nitride forming the substrate body, wherein the lower limit of the thickness of the coat layer is 5 μm, and the upper limit of the thickness of the coat layer is 10% of the thickness of the ceramic substrate, wherein a surface layer portion of an exposed surface on the placement surface side of the ceramic substrate is the coat layer, and wherein the coat layer has an optical reflectance of 50% or more for any light having a wavelength of from 300 to 800 nm.