Dependence of the structural, the electrical, and the optical properties on the Ar/O2 flow rate ratios for SnO2 thin films grown on p-InSb (111) substrates

SnO2 thin films on p-InSb (111) substrates were grown at various Ar/O2 flow rate ratio by using radio-frequency magnetron sputtering at low temperature. Atomic force microscopy images showed that the SnO2 films grown on the InSb (111) substrates at an Ar/O2 flow rate of 0.667 had the best surface morphologies among the several samples, and X-ray diffraction showed that the SnO2 thin films were polycrystalline layers. The capacitance-voltage measurements at room temperature showed that the majority carrier type of the unintentionally doped SnO2 film was n-type and that the carrier concentration of the unintentionally doped SnO2 film grown at an Ar/O2 flow rate of 0.667 had a minimum value of 4.28 × 1016 cm-3. Photoluminescence spectra at 10 K showed that peaks corresponding to the donor acceptor pair transitions were dominant and that the peak positions changed significantly depending on the Ar/O2 flow rate. These results indicate that the SnO2 epitaxial films grown on p-InSb (111) substrates at low temperature hold promise for potential optoelectronic devices based on InSb substrates.