BASIC RESEARCH ON CYCLOTRON RESONANCE.

A variety of experiments on the band structure of semimetals and semiconductors are described in this report. Helicon propagation experiments in semiconductors were performed and analyzed for the purposes of obtaining cyclotron effective masses of electrons in small-gap semiconductors for which conventional cyclotron resonance was impossible. In addition, the important solid state parameters, the carrier density, the mobility and the dielectric constant of the lattice were also measured by the same techniques. Cyclotron resonance in tellurium was carried out with considerable success in elucidating the valence and conduction band structure of tellurium crystals which were grown in the laboratory. The above experiments gave information about the Fermi surfaces of undeformed or intrinsic materials. In supporting work, the de Haas-van Alphen and Shubnikov-de Haas effects were studied in bismuth for purposes of examining the changes of band structure or band overlap produced by uniaxial stress. Interest in the band structure at points in the Brillouin zone removed from the Fermi surface made it interesting to perform reflectivity experiments in the visible and infrared regions. To support this effort, a unique reflectometer was constructed which has permitted higher sensitivity studies of the reflectivity than has been possible in other published work on the materials investigated, namely, Ge, Hg1-xCdxTe, GaAs, as well as Te. Author