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

摘要

[Object] To provide a gas monitoring device etc. with which gas monitoring can be performed at high sensitivity by using an InP-based photodiode in which a dark current is reduced without a cooling mechanism and the sensitivity is extended to a wavelength of 1.8 µm or more.;[Solution] An absorption layer 3 has a multiquantum well structure composed of group III-V semiconductors, a pn-junction 15 is formed by selectively diffusion of an impurity element in the absorption layer, and the concentration of the impurity element in the absorption layer is 5 × 1016/cm3 or less. The gas monitoring device detects a gas component and the like contained in a gas by receiving light having at least one wavelength of 3 µm or less.