Transport mechanisms in porous silicon layer and ZnO/PSL heterostructures

The transport mechanisms in both silicon porous layers (PSL) and ZnO/PSL/c-Si heterostructures were identified by Current-Voltage (I-V) measurements. The PSL were made by anodic etching of p-type (100) Silicon (Si) wafers with resistivity of 1-5 ¿-cm. The heterostructures were manufactured by depositing a zinc oxide (ZnO) film by DC-sputtering on the previously obtained PSL. The measured electrical resistivity of the ZnO films and the PSL were of 5.3 × 10⁵ and 5.7 × 10⁷ ¿-cm, respectively. The current flow in the PSL is limited by the space-charge regions (SCL), due to the charge trapped in the distinct energy localized states. For the heterostructures similar results were found, where the dominant transport mechanisms are associated to the physical characteristics of the PSL and the ZnO films. Accordingly a bandgap diagram for ZnO/PSL heterostructure is proposed, where the participation of the variety of the defect levels are considered.