Structural, Optical, and Electrical Properties of Hafnium–Aluminum–Zinc-Oxide Films Grown by Atomic Layer Deposition for TCO Applications

Abstract

ZnO is a widely studied material that exhibits versatile doping possibilities. Most research presents singly doped ZnO, leaving the potential of codoping unexplored. Within this study, hafnium–aluminum codoped zinc oxide (HAZO) thin films were grown on a glass substrate using the atomic layer deposition technique at 200 °C. A comprehensive analysis of the surface morphology and electrical and optical properties of the samples was conducted for varying the Al/Hf doping ratio. X-ray diffraction studies showed that the obtained films are polycrystalline, exhibiting a preferential growth direction along the (1 0 0) plane without any detectable precipitates. Moreover, the electrical measurements of HAZO films revealed that they exhibit lower resistivity (∼9.5 × 10–4 Ωcm) than the commonly used aluminum zinc oxide films (AZO). This improvement can be primarily attributed to the promotion of the n-type carrier concentration to 4.45 × 1020 cm–3 while maintaining a mobility value equal to 14.7 cm2/Vs. The doping also influences the optical properties of the material by widening the band gap and changing the refractive index, as observed by spectroscopy and ellipsometry studies. These findings highlight the potential of proposed HAZO thin films for future applications in electronic devices utilizing transparent conducting oxides.

Crystallization Disruption via Atomic Layer Deposition Substitutional Dopant Scheduling: High-Mobility Amorphous Indium Zinc Tin Oxide

“…As such, ALD is a viable choice for growing amorphous conducting oxides. Common amorphous TCOs grown by ALD include, indium zinc oxide (IZO), indium gallium oxide (IGO), indium gallium zinc oxide (IGZO), , indium zinc tin oxide (IZTO), , and hafnium aluminum zinc oxide (HAZO) . Sheng et al grew 40 nm amorphous IGO and IZO thin films at 200 °C that exhibited high charge carrier mobilities of 35 and 20 cm 2 V –1 s –1 , respectively, that were used as active layers in thin-film transistors. , In 2019, the same group fabricated indium gallium zinc oxide (IGZO) by plasma-enhanced atomic layer deposition.…”

SCAPS Modeling of CMTS Solar Cell with ZrS2 Buffer Layer

“…The present work explores a detailed numerical simulation of AZO/ZrS 2 /CMTS solar cell, where CMTS is used as an absorber layer, and ZrS 2 is used as a novel buffer layer, using solar cell capacitance simulator (SCAPS-1D) software. Al-doped ZnO is used as a window layer in simulation instead of pure ZnO as Al doping causes low resistivity, reduction in defect states, high transmittance and car-rier mobility, and as a result, enhances solar cell performance [47][48][49]. The influence of various parameters such as absorber layer thickness, acceptor concentration, electron affinity, bulk defect density of absorber, buffer layer thickness, donor concentration, bulk defect density of buffer, window layer thickness, bulk defect density of window, and interfacial defect density on the solar cell performance parameters open-circuit voltage (V oc ), shortcircuit current density (J sc ), fill factor (FF), and efficiency (η) are investigated and optimized to obtain the highest efficiency of the proposed solar cell.…”