Effect of isotopic mass on the photoluminescence spectra of beta zinc sulfide

TL;DR

This study investigates how isotopic mass variations in zinc sulfide crystals affect their photoluminescence spectra, revealing insights into electron-phonon interactions and vibrational contributions to bandgap renormalization.

Contribution

It provides the first detailed analysis of isotopic effects on the photoluminescence spectra of b-ZnS crystals, using a two-oscillator model to explain temperature dependence.

Findings

Isotopic mass influences free and bound exciton energies.

Zinc and sulfur vibrations contribute to bandgap renormalization.

Temperature dependence of bandgap energy is modeled effectively.

Abstract

Zinc sulfide is a wide bandgap semiconductor which crystallizes in either the wurtzite modification (a-ZnS), the zincblende modification (b-ZnS) or as one of several similar tetrahedrally coordinated polytypes. In this work, we report a photoluminescence study of different samples of isotopically pure b-ZnS crystals, and crystals with the natural isotopic abundances, at 15 and 77 K. The derivatives of the free and bound exciton energies on isotopic mass have been obtained. They allow us to estimate the contribution of the zinc and sulfur vibrations to the bandgap renormalization energy by electron-phonon interaction. A two-oscillator model based on the zinc and sulfur renormalization energies has been used to account for the temperature dependence of the bandgap energy in ZnS. The results are compared with those found for other tetrahedrally coordinated semiconductors.