This study explored the temperature-dependent characteristics of atomic layer-deposited (ALD) Hf-doped ZnO (HZO) films and the interface of HZO/p-Si and provides an optimum temperature window for the development of HZO layers. The films were deposited with a constant supercycle ratio (DEZ:TEMAHf = 10:1) at substrate temperatures (Tsub) between 150 and 350 °C. Results showed that the crystallinity of the films enhanced as Tsub increased from 150 to 250 °C with a minimal roughness (∼1.24 nm at 250 °C). Beyond 250 °C, the crystallinity deteriorated with an increased surface roughness (2.61 nm at 350 °C) along with void formation. Despite these variations, all the films maintained an average transmittance of over 70% in the visible and near-infrared regions of the spectrum. Hall effect measurements showed that the film deposited at 250 °C exhibited the lowest resistivity (1.39 mΩ cm) with a higher carrier concentration (∼5.21 × 1020 cm–3). Kelvin probe measurements revealed a distinctive temperature-driven evolution in the work function arising from modifications in film morphology and surface chemistry. Electrochemical impedance spectroscopy analysis of Al/HZO/p-Si/Al heterostructures demonstrated that the interfacial charge transfer is highly sensitive to Tsub with the lowest charge transfer resistance (Rct) at 250 °C, while higher Rct was observed at 150 and 350 °C. The results demonstrated that the Tsub of 250 °C is the optimal deposition temperature for achieving improved structural and electrical characteristics of the HZO film as well as enhanced interfacial characteristics of HZO/p-Si heterojunctions, showing its potential as a promising transparent conducting oxide layer for advanced electronic and optoelectronic applications.
Meenakshi et al. (Tue,) studied this question.