Optical Properties of Zn_1-xCd_xSe Epilayers Grown on (100) GaAs b y Molecular Beam Epitaxy

Abstract

Zn 1- x Cd x Se epilayers were grown on (100) GaAs substrates by molecular beam epitaxy. Lattice constants of the epilayers were measured by (004) rocking curve X-ray diffraction. A full width at half maximum of 475 to 2100 arcsec was obtained. The dependence of the energy gap on temperature, measured by the photoluminescence (PL) spectra, was fitted by Varshni's [Y. P. Varshni: Physica 34 149 (1967)] and O'Donnell's [R. P. O'Donnell and X. Chen: Appl. Phys. Lett. 58 2924 (1991)] models. The fitting parameters β (161 K to 368 K) and < h ν> (13 meV to 24 meV), related to phonon energy, were obtained from Varshni and O'Donnell fits, respectively. The activation energies calculated from the integrated PL intensity versus inverse temperature decrease as the Cd content increases. The broadening of the PL linewidth with temperature was fitted by Γ( T )=Γ 0 +Γ a T +Γ LO1 /[exp (\hbarω LO1 / k T )-1]+Γ LO2 /[exp (\hbarω LO2 / k T )-1]+Γ i exp (-< E b >/ k T ). The impurity binding energy, < E b >, was found to decrease as the Cd composition increases.