Energy bands and Wannier-Mott excitons in Zn(P_{1-x}As_{x})_{2} and Zn_{1-x}Cd_{x}P_{2} crystals

TL;DR

This study investigates how energy bands and excitonic properties evolve in mixed zinc phosphide-arsenide and zinc cadmium phosphide crystals at low temperatures, revealing nonlinear dependencies and increased potential fluctuations with composition.

Contribution

It provides detailed analysis of energy gap and excitonic series dependence on composition in mixed crystals, highlighting differences between two material systems.

Findings

Energy gap decreases slightly sublinearly with x in Zn(P_{1-x}As_{x})_{2}.

Rydbergs of excitonic series decrease superlinearly at small x in Zn(P_{1-x}As_{x})_{2}.

Linewidths of excitonic absorption increase with x, indicating increased potential fluctuations.

Abstract

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_{x}P_{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_{x}P_{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_{x}P_{2}. At the increase of x 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.