Abstract

We report, for the first time, on the strain related features of the near band-edge luminescence of ZnS epilayers and find emissions that can be related to both heavy-hole (hh) and light-hole (lh) character. Layers with different relative strain show well resolved peaks due to the recombination of excitons at neutral donors (D0,X) and acceptors (A0,X), as well as from free-to-bound transitions due to donors (D0,h) and acceptors (e,A0). The deepest emission (e,A0) follows the calculated shift of the hh band-edge, although manifestation of hh character is unexpected under the conditions of tensile biaxial strain. For the shallower excitonic emissions, the strain-induced lh shift is comparable to their smaller binding energy even for intermediate relative strain. Consequently bound lh exciton (BXlh) transitions dominate in the higher strained layers. Simple considerations based upon the hydrogenic description of excitons confirm these observations.

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