Investigation of strain in metalorganic vapor-phase epitaxy grown ZnTe layers by optical methods

We have studied the strain in ZnTe epilayers grown by atmospheric-pressure metalorganic vapor-phase epitaxy on (001) GaAs and GaSb substrates. Reflectivity and absorption measurements are performed at 2 K using single-crystalline layers with thicknesses of 0.2–2 μm. The biaxial strain in the samples caused by the lattice mismatch of layer and substrate is deduced from the splitting of the degenerate heavy- and light-hole exciton. A polariton model is used to describe the reflectivity structure at the E0 gap and to determine the transverse exciton energies. The deformation potentials obtained from an analysis of the absorption structures are a=−5.5 eV and b=−1.4 eV. The critical thickness for ZnTe/GaSb is lower than 0.8 μm near thermodynamic equilibrium. It also slightly depends on growth temperature which has its optimum at 345 °C.