Type conversion under hydrostatic pressure in ZnSe-ZnS strained-layer superlattices

A conversion from type-I to type-II in a ZnSe-ZnS strained-layer superlattice under hydrostatic pressure is observed. The hydrostatic-pressure dependence of the integrated intensity and the linewidth of the n=1 heavy-hole exciton emission spectra is represented by a couple of straight lines with a clear kink at about 31 kbar. Moreover, the emission peaks appear below the band-gap energy of the ZnSe well layers above 31 kbar. All of these features are well explained by the type conversion associated with the {Γ}-{Γ} conduction-band crossover between the ZnSe well and ZnS barrier layers.