ABSTRACT
Impurities in lead salts give rise to a wide range of unique properties. The role of impurity states appears to be important in lead chalcogenides for several reasons. This chapter presents the review of recent experimental results on doped lead chalcogenides. It focuses on the most interesting experimental facts related to the unusual properties of narrow-gap semiconductors. The chapter discusses the lead salts specially doped with different impurities. Doping of lead chalcogenides has been investigated for a large number of impurity species. According to the experimental database, the nonlinear dependence of carrier concentration on impurity content for doped lead chalcogenides is a rule rather than an exclusion. Infrared illumination possesses the widest range of possible excitation levels compared to other external factors.
