Lattice vibrational properties of ZnMgO grown by pulsed laser deposition

Vibrational modes were studied in n-type and p-type ZnMgO films doped with P (Mg composition of 7 at. %) grown by pulsed laser deposition on sapphire. The characteristic phonon frequencies were deduced from the analysis of IR reflectance measured by Fourier-transform spectroscopy. From comparison with similarly grown ZnO (P) films, Mg incorporation reduced the frequency of TO phonons by 14.5 cm(-1) and introduced two Mg related modes near 530 and 969 cm(-1). The first is likely to belong to the local vibrational mode of substitutional Mg, and the second is tentatively attributed to strongly lattice relaxed off-center Mg atoms. In addition, it was found that Mg incorporation triggers the formation of two phonon bands with characteristic frequencies of 501 and 634 cm(-1) that most likely belong to lattice defects. (C) 2007 American Institute of Physics.