Development of Mudulation Spectroscopy for Wide-Gap Semiconductors

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The purpose of this research is to establish the technique to analyze exciton condition, impurity condition, and so on in detail with characterizing the band structure of the wide-gap semiconductor in detail. Wide gap semiconductor material is remarkable recently, and development proceeds, and the research that it aimed at the laser application and the electron device application with various wide gap material is being done. In this new development of semiconductor material, detailed band structure evaluation by the optical research is being expected all the more. We developed the new electron-beam modulation spectroscopy that was suitable for the wide gap semiconductor evaluation, and got the following result.(1)We developed the electron-beam modulation spectroscopy system mounted on the scanning electron microscope(SEM). By utilizing this tequnique, we can perform the modulation spectroscopy from visible to vacuum ultraviolet light region. Furthermore, during the measurement, an exci … More tation area is evaluated with SEM.(2)Using our developed technique did characterization of bulk diamond crystal and diamond epitaxial films. Precise band-edge structure parameters are not sufficient because that band gap is huge, 5.5 eV, though applications as diamond electron devices are being expected. Here, band structure at the absorption edge of the diamond, band parameters and exciton states have been investigated.(3)Photoemission spectra were compared with electron-beam modulated reflectance signal, and important knowledge could get it about the change in the bound condition of excitons and the impurities states near the absorption edgeFrom our research results, we confirmed that the new type electron-beam modulation spectroscopy combined with SEM was effective in the wide gap semiconductor characterization. Moreover, it succeeded in obtaining the information related to band parameters, exciton states, the lattice strain, the piezo-electric field, the crystal defects, and so on from the spectrum analysis, and an outlook to the realization of this new technique was made. Less