Doping behavior of phosphorus in ZnO thin films: Effects of doping concentration and postgrowth thermal annealing

Effects of phosphorus concentration, [P], and postgrowth annealing on the x-ray diffraction and Raman scattering from ZnO:P thin films are presented. The ZnO (0002) diffraction peak exhibits a large monotonic angular shift with increasing [P] up to 5.1x10(19) cm(-3) while its shift upon annealing is dependent on [P]. No extrinsic phases were detected for the samples studied. Raman spectra reveal disorder-activated vibrational modes, around 276, 510, 582, and 643 cm(-1), with increasing [P]. They also reveal local vibrational modes corresponding to P(O) (similar to 370 cm(-1)) and P(Zn) (similar to 482 cm(-1)) upon annealing. The intensity evolution of the Raman features, together with the x-ray diffraction results, indicates that phosphorus substituting for zinc is favored at low annealing temperatures while increasing annealing temperature tends to convert phosphorus doping configurations from P(Zn) to P(O).