GAS MONITORING DEVICE, COMBUSTION STATE MONITORING DEVICE, SECULAR CHANGE MONITORING DEVICE, AND IMPURITY CONCENTRATION MONITORING DEVICE

摘要

Disclosed is a gas monitoring device that can reduce a dark current without a cooling mechanism and can monitor gas with high sensitivity using an InP type photodiode having a light-receiving sensitivity expanded to a wavelength of not less than 1.8 µm. The gas monitoring device is characterized in that the gas monitoring device comprises a light-receiving layer (3) having a multiquantum well structure of a group III-V semiconductor and pn junctions (15) formed by selective diffusion of an impurity element in the light-receiving layer, the concentration of the impurity in the light-receiving layer is not more than 5 × 1016/cm3, and the gas monitoring device receives light having at least one wavelength of not more than 3 µm to detect a gas component and the like contained in a gas.