Correlation between Hall Mobility and Optical Mobility in Aluminum‐Doped ZnO Films via Boundary Scatterings and Estimation of Donor Compensation Ratio

Abstract

A correlation between the Hall and optical mobility via boundary (BND) scatterings arising from grain as well as surface boundaries in radio frequency (RF) sputtered Al‐doped ZnO (AZO) films done by a comprehensive study on the electrical carrier transport and near infrared optical transmittance properties. AZO films with thicknesses from 100 to 1550 nm are grown by sputtering 1.9 wt% Al2O3‐doped ceramic target under identical growth conditions. The Hall measurement shows an increase in the carrier concentration value from 6.93 × 1020 to 1.1 × 1021 cm−3 with a mobility value (μHall) in the range of 4.98–10.3 cm2 (V s)−1 as the thickness increases. Unprecedentedly, it is shown that the optical mobility value (μopt) calculated using Drude theory is higher than that of the μHall up to a film thickness of ≈1000 nm beyond which both the values merges. Though the carrier concentration is higher than 5 × 1020 cm−3, BND scattering playing an important role in addition to the in‐grain scattering below a thickness of ≈1000 nm is demonstrated. Considering the BND scattering, donor compensation ratio is calculated and is uniquely found to vary with the film thickness.