Fabrication and Impedance Analysis of n-ZnO Nanorod/p-Si Heterojunctions to Investigate Carrier Concentrations in Zn/O Source-Ratio-Tuned ZnO Nanorod Arrays

摘要

Determination of the electrical properties of 1D semiconductor nanostructures is important for material and growth process development as well as for further nanodevice design. Gate-dependent electrical-transport measurements of single-nanowire field-effect transistors (FETs) have been employed to investigate the electrical-transport properties of semiconductor nanowires. However, it is time consuming to fabricate single-nanowire FETs. A more efficient method of determining the electrical properties of nanowires is needed. Here, we show that the carrier concentrations of well-aligned ZnO nanorods grown on p~(++)-Si substrates can be determined by means of ac impedance analysis of devices fabricated directly on as-deposited samples. The approach reported here is more convenient than the gate-dependent electrical-transport measurement. Using the ac impedance approach, we demonstrate that the carrier concentrations of the ZnO nanorods grown using metal-organic chemical vapor deposition (MOCVD) can be controlled in the range 3 x 10~(16) to 9 x 10~(17) cm~(-3) by varying the Zn/O source molar ratio (MR).