| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce an influence of a noise component and to manifest an absorption of a carbon by measuring a carbon concentration in a state such that a filter for shutting OFF a light having a specific wave number is provided before a photodetector. SOLUTION: A filter for shutting OFF a light having a wavelength of 1,000 cm-1 or more is installed before a photodetector in a background spectrum of a Fourier transform type infrared spectral altitude meter (FTIF) for a GaAs single crystal to be an object, a carbon concentration is measured, and an absorption distributed state is obtained. A region A of 1,000 cm-1 or more indicated by a shaded region in the drawing is shut OFF, and the light is incident only to a part of a region B. This incident light amount is remarkably small as compared with that of the case that the overall region of the wave number is an object, and an allowance takes places in the received capacity of the photodetector. Accordingly, when a diaphragm is opened in this state, a light amount of the region B near 580 cm-1 necessary to measure the carbon concentration can be increased. As a result, the absorption near the 580 cm-1 can be manifested, and the concentration can be measured by less number of integrations.</p> |
