Chapter 3 - Photothermal/Photoacoustic Spectroscopic Measurements of Optical Absorption Coefficients in Semiconductors

Abstract

Over the years, photothermal and photoacoustic-based spectroscopic techniques have proliferated as primary methodologies for measuring the optical absorption coefficient, α, in broad ranges of solids, which are not easily measurable by other more conventional spectroscopic techniques. It is noted that these techniques are now widely used to measure directly the optical absorption coefficient α (λ) from a dynamic measurement of the heat released via the spatial rate of optical-to-thermal energy conversion in a material, rather than the extinction coefficient, k (λ). The major α-measuring methodologies in this field include gas-cell and piezoelectric photoacoustic spectroscopy and various photothermal spectroscopies —such as photothermal beam-deflection spectroscopy, Fourier-transform infrared photoacoustic spectroscopies, and photopyroelectric spectroscopy. This chapter illustrates description of the techniques, their instrumental implementation, and finally applications to optical-property measurements of semiconductors, specifically at a single wavelength or within a spectral range.