Abstract
Excitonic absorption, reflection and photoluminescence spectra of mixed Zn(P<sub>1-χ</sub>As<sub>χ</sub>)<sub>2</sub> crystals over the full range of χ (0 ≤ χ 1) and Zn<sub>1-χ </sub>Cd<sub>χ</sub>P<sub>2</sub> crystals at 0 ≤ χ ≤ 0.05 have been studied at low temperatures (1.8 K). The decrease of the energy gap in Zn(P<sub>1-χ</sub>As<sub>χ</sub>)<sub>2</sub> at the increase of χ occurs slightly sublinearly. The rydbergs of excitonic series in this crystals decrease as well, and the dependences Ry(χ) for all series are strongly superlinear at small χ. In Zn(P<sub>1-χ</sub>As<sub>χ</sub>)<sub>2</sub> crystals the energy gap and rydbergs decrease at the increase of χ (at 0 ≤ χ ≤ 0.05) as well. The dependences of Eg and Ry on χ are considerably stronger in Zn(P<sub>1-χ</sub>As<sub>χ</sub>)<sub>2</sub> than in Zn<sub>1-χ</sub>Cd<sub>χ</sub>P<sub>2</sub>. At the increase of χ the half-width of excitonic absorption lines increases monotonically in both type crystals that is evidence of the increasing role of fluctuations of crystal potential.
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