Some Optical Properties of CdSe Single Crystals

Abstract

Optical transmission and reflection measurements were made on a single crystal of CdSe (crystal class ${C}_{6v}$) with light polarized parallel and perpendicular to the $c$ axis. The absorption coefficients, ${\ensuremath{\mu}}_{\ensuremath{\perp}}$ and ${\ensuremath{\mu}}_{\mathrm{II}}$, were determined and are presented as functions of incident photon energy, at room temperature. The selection rule, ${\ensuremath{\mu}}_{\ensuremath{\perp}}>{\ensuremath{\mu}}_{\mathrm{II}}$, expected for all solids in the crystal classes ${C}_{\mathrm{nv}}$ and ${C}_{n}$, where $n=3, 4, or 6$, is very well obeyed in CdSe. The absorption coefficients are not simple functions of the photon energy, but are nearly exponential and almost follow Urbach's rule.The fluorescence of the single crystal has been measured at 77\ifmmode^\circ\else\textdegree\fi{}K. It is peaked at 920 m\ensuremath{\mu} and it is slightly polarized perpendicular to the $c$ axis. The results are similar to what has been obtained for hexagonal ZnS.