Optical and electrical properties of ZnSeO alloys grown by plasma-assisted molecular beam epitaxy

ZnSeO alloys with O composition to 11.5% were grown on sapphire substrates by plasma-assisted molecular beam epitaxy. The absorption coefficients, α(hω), determined from the transmittance measurements are higher than 1 × 10⁴cm^-1 for these ZnSeO thin films and manifest themselves very suitable for photovoltaic devices. The absorption coefficient following the square law of photon energy indicated that the ZnSeO has a direct band gap. Based on the quadratic band gap function, a bowing parameter of 6.9 eV was obtained. Cl doping in ZnSeO films grown on GaAs substrates were first demonstrated with carrier electron concentration varying from 1.2 × 10¹⁷cm^-3 to 5.4 × 10 ¹⁸cm^-3 with 2.2% oxygen content. The activation energy of 123 meV for Cl dopant in ZnSeO was also deduced from temperature dependent Hall measurements.