The effective surface Debye temperature of Yb:GaN

The effective Debye temperature of ytterbium and gallium in Yb:GaN thin films has been obtained using X-ray photoemission spectroscopy. The vibrational motion normal to the surface results in a dimunition of photoemission intensities from which we have estimated the effective Debye temperatures of 221±30 K and 308±30 K for Yb and Ga, respectively. The difference between the measured values for Yb and Ga suggests that the Debye temperatures are influenced by the local environment. The smaller effective surface Debye temperature for Yb correlates to a soft, strained surface, possibly due to an increased Yb―N bond length as compared to the Ga―N bond length.