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Selective photoconductivity at frequency ω=155 cm-1 was discovered in PbTe(Ga) narrow-gap semiconductors at liquid-nitrogen temperatures. The corresponding energy is much lower than all characteristic energies of the electronic spectrum of the semiconductor. The effect is attributed to optical excitation of a local vibrational mode of an impurity center leading to delocalization of the electrons. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The kinetics of variation in the resistance of PbTe:Ga single crystals, with their Fermi level pinned within the band gap, during annealing at temperatures of up to 400°C was studied for the first time. It is shown that annealing the crystals for only several minutes at 200-250°C leads to the transformation of the material, which is semi-insulating at low temperatures, into a strongly degenerate semiconductor with a free electron concentration of about 10[sup -18] cm[sup -3]. In other words, annealing results in the decomposition of DX-like impurity centers, which account for Fermi level pinning within the PbTe:Ga band gap. The corresponding activation energy is determined. It is found that high-temperature annealing at about 400°C promotes the tendency to a partial recovery of semi-insulating properties. [ABSTRACT FROM AUTHOR]

A new model is proposed for DX-like impurity centers, which are responsible for the Fermi-level stabilization and long-term relaxation effects in IV-VI semiconductors doped with group III elements. The model is based on the idea of a variable valence of the impurity, whereas the nature of the long-term effects at low temperatures is associated with the formation of an effective barrier caused by a change of two units in the impurity valence upon photoexcitation. The model is applied to an analysis of the photoconductivity spectra in PbTe(Ga). The model can also be applied to the classical DX centers in III-V semiconductors. [ABSTRACT FROM AUTHOR]

We have compared directly the performance of a Pb[sub 1-x]Sn[sub x]Te(In) photodetector with that of two other state-of-the-art far-infrared detectors: a Si(Sb) blocked impurity band (BIB) detector and a Ge(Ga) photoconductor in an integrating cavity. The Pb[sub 1-x]Sn[sub x]Te(In) photodetector has current responsivity S[sub I] several orders of magnitude higher than the Si(Sb) BIB at wavelength λ=14.5 μm. Persistent photoresponse with S[sub I]∼10[sup 3] A/W at 40 mV bias and 1 s integration time at the wavelengths λ=90 and 116 μm has also been observed in the Pb[sub 1-x]Sn[sub x]Te(In) photodetector. This is larger by a factor of ∼100 than the responsivity of the Ge(Ga) photoconductor in the same conditions. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]