| MBE growth and substrate related defects in mercury cadmium telluride (Hg1-xCdxTe) limit the performance of complex infrared devices (e.g. large focal plane arrays). A fundamental understanding of the underlying mechanism of defect formation and their characterization is needed. We have developed a novel experimental apparatus suitable for non-destructive optical characterization of these defects. It is based on Fourier Transform Infrared (FTIR) Spectroscopy. The apparatus is capable of measuring spectrally resolved photoluminescence, transmittance and photo-transmittance with high (diffraction-limited) spatial resolution in the infrared portion of the spectrum. In order to get quantitatively accurate FTIR spectra, we have also developed a new error-free algorithm for phase correction of FTIR interferograms using digital all-pass filters. With this apparatus, we have studied microscopic and macroscopic defects by analyzing spatial photoluminescence images (for macroscopic defects) and the temperature dependence of photoluminescence spectra (for microscopic defects - impurities). Defect levels were identified and their spatial distribution analyzed. Also, the effect of substrate surface preparation on the defects in the epilayer was studied. It was shown that photoluminescence study can be an effective tool in the optimization of MBE growth of Hg1-xCdxTe epilayers. |
