Long-wavelength PbSnTe/PbTe inverted heterostructure mosaics

Abstract

Pb0.76Sn0.24Te/PbTe inverted heterostructure mosaics were fabricated from epilayers grown by a liquid-phase-epitaxy technique. At 85 K, the spectral peak of these diodes occurred at 13 μm with a spectral cutoff at 14.2 μm. This response is believed to be one of the longest that has ever been reported for PbSnTe infrared detectors near LN2 temperature. The spectral cutoff, as expected, shifted toward a longer wavelength as the temperature was lowered; however, it reached a maximum at 30 K, beyond which the spectral response exhibited a retrograde characteristic. This behavior is explicable from the combined temperature dependencies of the energy gap, the Fermi level, and the thermal broadening of the optical transitions.