Strain relaxation and its effect in exciton resonance energies of epitaxial ZnO layers grown on 6H-SiC substrates

Thickness-dependent strain relaxation and its role on exciton resonance energies of epitaxial ZnO layers grown on 6H-SiC substrates have been studied. The magnitudes of strain were determined experimentally by x-ray diffraction measurements. The strain ratios under biaxial stresses (Δc/c₀)/(Δa/a₀) of epitaxial ZnO layers grown on SiC and Al₂O₃ substrates were estimated to be 0.38 and 0.50, respectively. The strain-induced band shift δE_A/δε_zz for ZnO/SiC and ZnO/Al₂O₃ heterostructures was analyzed by photoluminescence with the values of 13.1 and 14.6 eV, respectively. These comparative strain-induced band shifts, as well as Poisson ratios, evidenced the role of lattice deformation kinetics induced by different lattice mismatches in the ZnO/SiC and ZnO/Al₂O₃ heterostructures. © 2004 American Institute of Physics.