Higher-interband electroreflectance of long-range ordered Ga0.5In0.5P.

Abstract

Ordering-induced higher-interband transitions in long-range ordered ${\mathrm{Ga}}_{0.5}$${\mathrm{In}}_{0.5}$P alloys have been investigated by electroreflectance-polarization spectroscopy. Energy positions of the ${\mathit{E}}_{1}$ transitions show strong order-parameter dependencies together with changes in their signal intensities. For the ${\mathit{E}}_{1}$ transitions, we resolved three components; two components shift to the lower-energy side with increasing order parameter, and the other one shifts to the higher-energy side. The ${\mathit{E}}_{1}$+${\mathrm{\ensuremath{\Delta}}}_{1}$ edge also shifts to the lower-energy side with increasing order parameter. For the ${\mathit{E}}_{2}$ transitions strong change was found in its oscillator strength. In the [1\ifmmode\bar\else\textasciimacron\fi{}11]-CuPt ordering in ${\mathrm{Ga}}_{0.5}$${\mathrm{In}}_{0.5}$P, the ${\mathit{L}}_{1\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}11}$ of the high-symmetry point of the zinc-blende Brillouin zone folds into the \ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{} point in the reduced superlattice symmetry. The other three zinc-blende L points and three X points fold into the D\ifmmode\bar\else\textasciimacron\fi{} point in the reduced symmetry. Interactions in the superlattice--Brillouin zone cause such variations in the ${\mathit{E}}_{1}$ and ${\mathit{E}}_{2}$ transitions. The ordering-induced evolution of the transition energy is consistent with the recent theoretical prediction. \textcopyright{} 1996 The American Physical Society.