Study of stable p-type conductivity in bismuth-doped ZnO films grown by pulsed-laser deposition

Bismuth-doped p-type ZnO films were grown on sapphire (0001) substrates by pulsed-laser deposition at 600 ○C in 1 mT oxygen pressure. The photoluminescence (PL) property of the as-grown and post-annealed Bi-doped p-type ZnO films at 10–300 K has been investigated. A well-resolved PL spectrum was obtained with acceptor bound exciton emission and conduction band to acceptor transition giving direct evidence for the creation of acceptors. The acceptor energy level of the bismuth dopant is found to be 0.13 eV above valance band. The binding energy between the acceptor and the exciton measured as a function of temperature was found to be 14 meV. A hole concentration of 5.36×1018cm−3 and a mobility of 8.9 cm2/Vs was obtained for 3% bismuth-doped and annealed ZnO thin films. This study suggests that bismuth is an excellent dopant to obtain stable and reproducible p-type conductivity in ZnO for the application in optoelectronic devices.