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Abstract
Low temperature infrared wavelength modulation spectroscopy was implemented and applied to studies of the deep levels in undoped semi-insulating Gallium Arsenide, grown by the liquid encapsulated Czochralski technique. The absorption bands near 0.37 eV were attributed to accidental iron impurity. An absorption band observed at 0.4 eV was shown to be due to a multi-level defect complex, annealable at about 450(DEGREES)C. The photo-quenching of the absorption coefficient in the spectral region of 0.7-1.4 eV, due to the EL2 levels, was utilized to assess the accuracy of the conventional room temperature optical absorption spectroscopy in measuring the EL2 and Chromium concentrations and a more accurate method for such measurements was suggested. Re-examination of the wavelength modulation photoresponse spectroscopies showed that the line shapes obtained by these methods are subject to distortions from several sources of spurious interference spectra limitations of these methods in studies of the deep levels and the interband transitions in semiconductors are discussed and a practical method for removal of the distortions due to the background spectra is suggested. Finally, a comparison was made between the wavelength modulation absorption/reflection and the wavelength modulation photoresponse spectroscopies. It was concluded that the former are the most suitable modulation techniques for the above studies, since besides other advantages, they are nondestructive and yield unambiguous line shapes.