Visible and Ultraviolet Reflectivity of Mercury - - Telluride.

The visible and ultraviolet reflectivity of Hg(,1 -x)Cd(,x)Te bulk samples with 0.177 (LESSTHEQ) X (LESSTHEQ) 0.335 were measured from 2.0 to 8.8 eV and from 8.8 to 300K. The dependences of four interband transitions, E(,1), E(,1) + (DELTA)(,1), A, and B, upon composition and temperature were determined for surfaces that were polished and then etched. The effects of surface preparation were studied. The reflectance was measured using a computer-controlled, vacuum, ultraviolet spectrometer constructed for the experiment. Several new results are reported. Wavelength -modulated reflectivity was performed successfully on HgCdTe at room temperature, in the visible, using a plexiglass refractor plate. All of the low temperature (< 100K) reflectivity measurements indicate a temperature coefficient about -5 x 10('-4) eV/K, similar to results previously reported for temperatures above 100K. A new, hydrogen-like, continuum, light source in the region from 200 to 300 nm was discovered, using a 4% H(,2) in Ar gas mixture. Previously, much importance has been placed on small shifts in spectral reflectance features, presumed to be caused by changes in composition due to processing. Calculations of the reflectivity, when surface roughness is taken into account, show that roughness also produces such shifts. These calculations and their implications are described in detail.