MOISTURE DETECTOR, BIOLOGICAL BODY MOISTURE DETECTOR, NATURAL PRODUCT MOISTURE DETECTOR, AND PRODUCT/MATERIAL MOISTURE DETECTOR

摘要

A moisture detector includes a light-receiving element including an absorption layer having a pn-junction, or an array of the light-receiving elements, wherein the absorption layer has a multiquantum well structure composed of a Group III-V semiconductor, the pn-junction is formed by selectively diffusing an impurity element into the absorption layer, and the concentration of the impurity in the absorption layer is 5×1016/cm3 or less. The moisture detector receives light having at least one wavelength included in an absorption band of water lying in a wavelength range of 3 μm or less, thereby detecting moisture.