Compressive strain induced heavy hole and light hole splitting of Zn1−xCdxSe epilayers grown by molecular beam epitaxy

Compressive strain induced heavy hole and light hole splitting of the Zn1−xCdxSe epilayers grown by molecular beam epitaxy was studied by the reflectivity spectra. Heavy hole exciton (HHX) and light hole exciton (LHX) splittings for the ZnSe, Zn0.999Cd0.001Se, Zn0.987Cd0.013Se, and Zn0.974Cd0.026Se epilayers are 12.6, 14.0, 17.2 and 20.4 meV, respectively. HHX and LHX energy splitting depends linearly on the Cd composition. No strain relaxation was observed in these thin (about 50 nm) Zn1−xCdxSe epilayers. A simplified dielectric model was used to fit the reflectivity spectra. At 10 K, the obtained oscillator strength and broadening parameter are about 2.7×10−2 eV2 and 2.6 meV for HHX and 1.2×10−2 eV2 and 2.6 meV for LHX. Temperature dependence of HHX and LHX transition energy was fitted by Varshni’s and O’Donnell’s model. No clear temperature dependence was found for the HHX and LHX splitting.