High-Power Microwave-Assisted Ga Doping, an Effective Method to Tailor n-ZnO/p-Si Heterostructure Optoelectronic Characteristics

Abstract

High-power microwave-assisted gallium (Ga) -doped ZnO nanorods (MGZRs) are grown on p-Si substrates, and their optoelectronic characteristics are reported. Gallium nitrate hydrate is mixed with zinc nitrate hexahydrate and hexamethylenetetramine to make 1, 2, and 5% MGZRs in a domestic microwave oven. The MGZR diameter decreased when doping increased from 1 to 2%, but the diameter of the highly doped (5%) sample significantly increased. The EDS results confirm the incorporation of Ga atoms in the ZnO crystal lattice, where an increase in the dopant concentration in growth solution increase the probability of Ga ion incorporation into ZnO crystal lattice. However, exact values for EDS quantification are not found because of Si peaks from the substrate. The high-intensity photoluminescence UV peaks associated to exciton recombination are blue-shifted, and some defects are incorporated by Ga, which respond to the visible and near-IR regions in MGZRs. Furthermore, the n-MGZR/p-Si heterostructures show a diode-like I-V response, where the current levels increase when the doping concentration increase because of an increase in carrier concentration in MGZRs, which is confirmed by Hall-effect measurements. The MGZRs address the low carrier transport issues in undoped microwave-assisted nanorods and are notably effective in altering their optoelectronic characteristics.