Patent ID: 8624189

Claim:
A gas monitoring device for monitoring a gas using light in the near-infrared region with a wavelength range of 3 μm or less, the gas monitoring device comprising: a light-receiving element that receives light in the near-infrared region, wherein the light-receiving element includes an absorption layer formed on an InP substrate and having a multiquantum well structure, the absorption layer has a bandgap wavelength of 1.8 μm or more and 3 μm or less; and a diffusion concentration distribution control layer is disposed on a surface side of the absorption layer, the surface side being opposite the InP substrate, the diffusion concentration distribution control layer has a bandgap smaller than that of InP, in the light-receiving element, a pn-junction is formed by selectively diffusing an impurity element through the diffusion concentration distribution control layer so as to reach the absorption layer, the concentration of the impurity element in the absorption layer is 5×10 16 /cm 3 or less, and the light-receiving element receives light from the gas, the light having at least one wavelength of 3 μm or less, to detect a gas component and the like contained in the gas.