Platinum Schottky contacts on single-crystal ZnO with hydrogen peroxide treatment

摘要

Platinum (Pt) Schottky contacts (SCs) on hydrothermal grown Zn-terminated (0001) ZnO substrates with the different hydrogen peroxide (H_2O_2) treatment time are investigated. Under the treatment in room temperature, effective SCs are made for 45 min and longer time and the electrical characteristics show the dependence on treatment time. The irregular humps on ZnO surface with roughness measured by atomic force microscope differ as the treatment time and roughness exhibits the large variation between 0.368 and 3.566 nm, indicating the etching effect and near-surface defects related to the lattice imperfections. The evaluated barrier height has the value at 0.89-0.96 eV with the saturation current density in the range of 2.21 × 10~(-10)-3.31 × 10~(-9) A/cm~2. The effective donor concentration calculated from capacitance-voltage (C-V) measurement decreases as treatment time, implying the widening of the space charge region after H_2O_2 treatment. The improved SC characteristics are attributed to the product of the wider bandgap and low-conductivity ZnO_2 via grazing-incidence x-ray diffraction analysis. The rectifying behavior has the threshold dependence on the treatment time and has the reverse trend toward the surface asperities.