PbCaTe films and PbCaTe/PbTe superlattices prepared by hot-wall epitaxy

PbCaTe films, and PbCaTe/PbTe and CaTe/PbTe superlattices were prepared by hot-wall epitaxy for application to mid- and far-infrared lasers of the 4 t o 20 mu m range. The PbCaTe ternary alloy shows good lattice matching with PbTe, and high carrier concentration films with a band gap wider than 650 m eV were obtained by doping Bi and Tl as donor and acceptor impurities, resp ectively. PbCaTe/PbTe and CaTe/PbTe superlattices with very thin CaTe layer s were also prepared. Optical transmission measurements were performed for the superlattices. Steplike interband absorption due to two the dimensional density of states of the superlattices was observed at room temperature. T he absorption edge of the PbCaTe/PbTe superlattices agreed well with the th eoretical values calculated by the envelope-function approximation.