Post-growth annealing study of heavily Ga-doped zinc oxide grown by radio frequency magnetron sputtering

Abstract

Heavily doped Ga-doped ZnO (resistivity ∼8 × 10−4 Ω cm and optical transmittance 96%) were fabricated by radio frequency magnetron sputtering. Post-growth annealing studies in H2–Ar and pure Ar atmospheres were conducted. No noticeable thermal-induced change in the Ga depth profile or in the Ga chemical state was found in both atmospheres up to 600 °C. The Burstein–Moss effect was exhibited in the effective optical band gap, and the cathodoluminescence (CL) photon energy of the near band edge emission. CL emission related to VZn persisted after the 600 °C annealing. The thermal evolutions of the carrier concentrations were nearly identical for both annealing atmospheres. The carrier mobility increased upon annealing in H2/Ar and remained effectively unchanged in pure Ar. The observed changes in carrier concentration and mobility were tentatively associated with VZn, or other compensating defects, which have concentrations as high as 1019–1020 cm−3.