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Nature of the band gap in Zn 1 − x Be x Se alloys

2000; American Physical Society; Volume: 61; Issue: 8 Linguagem: Inglês

10.1103/physrevb.61.5332

1095-3795

C. Chauvet, E. Tournié, J. P. Faurie,

Semiconductor Quantum Structures and Devices

We have investigated by low-temperature photoluminescence and reflectivity spectroscopies a series of ${\mathrm{Zn}}_{1\ensuremath{-}x}{\mathrm{Be}}_{x}\mathrm{Se}$ alloys with x up to 0.70. This allows us to locate precisely the direct-to-indirect band-gap crossover at $x=0.46\ifmmode\pm\else\textpm\fi{}0.01.$ We demonstrate that above this composition the indirect band gap corresponds to a $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\Gamma}}X$ transition. By extrapolation we determine the $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\Gamma}}X$ band gap of BeSe at $3.75\ifmmode\pm\else\textpm\fi{}0.1\mathrm{eV}.$ Finally, we find a bowing parameter $b=0.97\mathrm{eV}$ for the $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\Gamma}}\ensuremath{\Gamma}$ direct band gap in the whole composition range. For $x<~0.60,$ this band gap increases linearly with the Be content at a rate of 23 meV/% Be.