Comparison study of energy bands and Wannier-Mott excitons in mixed Zn(P_(1-x)As_x)_2 and Zn_(1-x)Cd_xP_2 crystals

摘要

Excitonic absorption, reflection and photoluminescence spectra of mixed Zn(P_(1-x)As_x)_2 crystals over the full range of x (0 ≤ x ≤ 1) and Zn_(1-x)Cd_xP_2 crystals at 0 ≤ x ≤ 0.05 have been studied at low temperatures (1.8 K). The decrease of the energy gap in Zn(P_(1-x)As_x)_2 at the increase of x occurs slightly sublinearly. The rydbergs of excitonic series in this crystals decrease as well, and the dependences Ry(x) for all series are strongly superlinear at small x. In Zn_(1-x)Cd_xP_2 crystals the energy gap and rydbergs decrease at the increase of x (at 0 ≤ x ≤ 0.05) as well. The dependences of E_g and Ry on x are considerably stronger in Zn(P_(1-x)As_x)_2 than in Zn_(1-x)Cd_xP_2. At the increase of x the half-width of excitonic absorption lines increase monotonically in both type crystals that is evidence of the increasing role of fluctuations of crystal potential.