A novel phenomenon: p-Type ZnO:Al films deposited on n-Si substrate

Al-doped p-type ZnO thin films were fabricated by RF magnetron sputtering on n-Si (1 0 0) and homo-buffer layers in pure ambient oxygen. ZnO ceramic mixed with 2 wt% Al2O3 was selected as a sputtering target. XRD spectra show that the Al-doped ZnO thin films have a ZnO crystal structure. Hall Effect experiments with Van der Pauw configuration show that p-type carrier concentrations are arranged from 1.66×1016 to 4.04×1018 cm−3, mobilities from 0.194 to 11.1 cm2 V−1 s−1 and resistivities from 0.999 to 18.4 Ωcm. Field emission scanning electron microscopy (FESEM) cross-section images of different parts of a p-type ZnO:Al thin film annealed at 800 °C show a compact structure. Measurement of the same sample shows that density is 5.40 cm−3, smaller than the theoretically calculated value of 5.67 cm−3. Photoluminescence (PL) spectra at 10 K show a shoulder peak of p-type ZnO film at about 3.117 eV ascribed to electron transition from donor level to acceptor level (DAP).