Tl incorporation in InSb and lattice contraction of In1-xTlxSb

Ternary In1-xTlxSb thin films are grown by low pressure metalorganic chemical vapor deposition in the high In composition region. Infrared photoresponse spectra of the In1-xTlxSb epilayers show a clear shift toward a longer wavelength compared to that of InSb. Tl incorporation is confirmed by Auger electron spectroscopy. In contrast to the theoretical expectation, high resolution x-ray diffraction study reveals that the lattice of the In1-xTlxSb epilayers is contracted by the incorporation of Tl. As more Tl is incorporated, the lattice contraction is observed to increase gradually in the experimental range. A possible origin of this phenomenon is discussed. Our experimental results suggest that the Tl incorporation behavior in In1-xTlxSb differs from that of other group III impurities in III antimonides. (C) 2000 American Institute of Physics. [S0003-6951(00)02103-3].