Electronic properties of ZnO nanorod MIS structure

Recently, there has been substantial interest in the study on the electronic properties of hybrid structures. In particular, ZnO nanorods are a good n-type material that can be formed at low temperature using solution deposition techniques complementing the availability of numerous p-type organic semiconductors. Furthermore, there is evidence suggesting that ZnO nanorods can act as efficient electron injectors making them ideally suitable for use in opto-electronic devices such as the light-emitting diodes and transistors. This work examined the electronic properties of ZnO nanorods deposited using spin coating and hydrothermal techniques as an n-type layer and we measured the carrier density and mobility using thermoelectric and Hall measurements. In the context of a hetero-structure device, we used the ZnO nanorods to form metal–insulator-semiconductor (MIS) diodes and measured the capacitance–voltage ( C – V ) characteristics. Our results suggested that the semiconductor-insulator interface was in depletion at equilibrium and moved away from depletion at both positive and negative (gate) biases. The computed carrier density based on the C – V measurements was essentially the same as what was found in the thermoelectric measurements leading to the argument that charge flow in the MIS structures had been primarily along the long axes of the nanorods. The dynamic C – V characteristics also suggested that there could be substantial (negative) charge states at the insulator-semiconductor interface that readily supplied electrons to the depletion layer.