Characterization of optical and thermal properties of chalcopyrite compound semiconductors by photoacoustic spectroscopy

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In this research project, we have investigated an application of photoacoustic spectroscopy to characterization of optical and thermal properties of multinary compound semiconductors. We employed a gas-microphone method as a measurement method, and analyzed the conditions to evaluate the optical absorption coefficients and the thermal diffusivities of these materials. Following results are obtained.1. In the case of using plate type CdS specimen having the thickness less than 2mm, we have good agreement between experimental results and theoretical ones based on the RG theory. For the specimens having thickness larger than 2mm, the difference between the experimental results and the theoretical ones was observed.2. A better technique for the measurements of the photoacoustic spectra of powders was investigated. The dilution method where a powder to be measured is diluted in a transparent matrix powder is found to be better than that with an undiluted powder sample. By means of the theory including sounds coming from the inside parts of the specimen, we have found a good agreement of the theoretical results with the experimental results. To compare with the PA signal of carbon specimen, the optical absorption coefficients of powdered materials were obtained.3. Photoacoustic spectra of CuGaS_2, TlGaSe_2, TlInS_2 were investigated in conjunction with photoconductivity spectra and transmission spectra of these semiconductors.