| Lead telluride-based alloys are narrow-gap semiconductors that are extensively used in the infrared optoelectronics. Performance of the respective devices is to a great extent restricted by high number of growth defects giving rise to high free carrier concentration in the as-grown materials. Doping of the lead telluride-based alloys with some of the group III impurities, for instance, In, Ga, Tl, results in appearance of new effects that are not characteristic for the undoped material, such as Fermi level pinning and persistent photoconductivity at low temperatures. Features of these effects suggest that the impurities reveal the mixed valence behavior, and that the charge states of impurity centers are correlated. We discuss the experimental results obtained recently in the field and their interpretation within the framework of existing theories. |
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