Al/F codoping effect on the structural, electrical, and optical properties of ZnO films grown via atomic layer deposition

Abstract

Aluminum/fluorine-codoped zinc oxide (AFZO) thin films were prepared on silicon and glass substrates through atomic layer deposition at 150 °C. Their structural, electrical, and optical properties were investigated as functions of the F/Al codoping ratio. The X-ray diffraction analysis revealed that the preferred growth orientation changed depending on the codoping with F, that is, from (0002) for Al-doped ZnO (AZO) films to (1010) for the AFZO ones. The electrical resistivity of the AFZO films (around 5.0 × 10–4 Ω∙cm) was lower than that of the AZO ones; this was mainly attributed to an increase in the n-type carrier concentration (from 4.11 × 1020 cm3 for AZO to 5.86 × 1020 cm3 for AFZO) due to the substitution of the Zn and O sublattice sites by, respectively, the Al and F atoms. The enhanced carrier concentration affected also the optical property of the AFZO films according to the Moss–Burstein shift. The carrier mobility was similarly improved (from 6.96 cm2/V∙s for AZO to 21.2 cm2/V∙s for AFZO) by the passivation of the oxygen vacancies via the F-doping.