Photomodulated infrared spectroscopy by a step-scan Fourier transform infrared spectrometer

A technique is developed for photomodulated spectroscopy in a long-wavelength region, based on a step-scan Fourier transform infrared spectrometer. The experimental setup is discussed, and photoreflectance (PR) spectra of narrow-gap HgCdTe materials are given as examples at the wavelengths of 5 and 9 μm. The photoluminescence spectra suggest that the PR features are related to the material fundamental gap. The signal-to-noise ratio and spectral resolution of the PR spectrum are quite good for line-shape analysis. The results indicate that the PR spectrum can be well fitted by a third-derivative line-shape function. Advantages and extendability are emphasized, and the potential for advancing the study of narrow-gap materials' band structures is foreseen.