Fabrication and Temperature Dependent Electrical Characterization of n-ZnO Nanowires/p-Si Substrate Heterojunction Diodes

In this paper, we report the growth of n-ZnO nanowires on p-silicon (Si) substrate by simple thermal evaporation processing using metallic zinc powder in presence of oxygen gas at 650 degrees C. The grown nanowires were examined in terms of its morphological, structural and optical properties. The morphological characterization by field emission scanning electron microscopy (FESEM) revealed the high density growth of quasi-aligned ZnO nanowires on the silicon substrate. The X-ray diffraction pattern revealed that the nanowires are well-crystalline and possess wurtzite hexagonal phase of ZnO. The room-temperature photoluminescence (PL) spectra of grown nanowires exhibited a sharp and strong UV emission and a suppressed green emission which revealed that the grown nanowires possess well-crystallinity and less structural defects. A heterojunction diode was fabricated based on n-ZnO nanowires/p-Si substrate assembly and temperature dependent electrical properties were examined. The fabricated heterojunction diode exhibits a change in the forward current between similar to 4 mA and similar to 12 mA due to the increase in temperature from 30 degrees C to 100 degrees C at a turn-on voltage of similar to 5.0 V. The low values of series resistance (similar to 38 Omega and similar to 13 Omega at 30 degrees C and 100 degrees C, respectively) determined in the forward bias condition might cause reasonable reduction in any possible partial drop in the output current of the whole assembly. This is an indication that the effect of shunt resistance is minimal. The obtained values of quality factors suggest that the fabricated device exhibit inhomogeneity at the interface and good stability over change in temperatures.