Optical Absorption in HgTe and HgCdTe

Abstract

Absorption and reflectivity near the fundamental absorption edge have been measured in the HgTe-CdTe alloy series for CdTe concentrations of up to 28%. In the HgTe rich region, the edge shifts to longer wave-lengths with decreasing temperature. For HgTe, the absorption rises to 2\ifmmode\times\else\texttimes\fi{}${10}^{4}$ ${\mathrm{cm}}^{\ensuremath{-}1}$ at $\ensuremath{\hbar}\ensuremath{\omega}=0.6$ eV. Absorption did not decrease below 1.4\ifmmode\times\else\texttimes\fi{}${10}^{3}$ ${\mathrm{cm}}^{\ensuremath{-}1}$ at room temperature. The theory of optical absorption in zincblende compounds is reviewed. Absorption in this alloy series agrees with theory for direct transitions with an energy-independent matrix element evaluated by Kane for InSb. Analysis of reflectivity in HgTe indicates an electron effective mass of $0.02m$ at 100\ifmmode^\circ\else\textdegree\fi{}C.