Progress of IV-VI Semiconductor Research in China

Progress of IV-VI semiconductor (lead chalcogenides) research in China is reported. Lead chalcogenides (PbSe and PbTe) have been grown by molecular beam epitaxy (MBE) [1]. Evolution of PbSe surface morphologies with different Se/PbSe beam flux ratio has been studied by atomic force microscopy (AFM) and high-resolution x-ray diffraction (HRXRD). Interesting surface features, such as triangle holes and spirals with monolayer steps, are observed by AFM. Glide of threading dislocations in {100}-glide system and Pb-rich atom agglomeration play an important role in the formation of triangle pits. PbSe QDs grown by self-organization and mid-infrared luminescent emission of the QDs at room temperature are demonstrated. Phonon modes of PbTe and PbSe epitaxial film are studied by Raman spectroscopy in detail. Phonon modes of epitaxial PbTe films grown by molecular beam epitaxy on BaF2 (111) substrate have been studied by micro-Raman scattering [2]. On the as-grown PbTe surface strong TeO2 phonon vibrational modes were detected, which is believed to silence the observation of the first-order longitudinal optical phonons at the ?-point of the Brillouin zone of PbTe in early conventional Raman scattering experiments. The existence of TeO2 layer on PbTe surface is affirmed by XPS observations. After removal of TeO2 layer on surface of PbTe, the LO phonons for epitaxial PbTe film were unambiguously observed.