Vibrational signature of the SiN defect in Si-doped GaN_xAs _(1-x)

摘要

Using first principles density functional theory in a supercell approach, we calculate the full spectrum of localized vibration modes associated with the SiN defect complex in GaAs. Two recently proposed structures are investigated in detail: (a) substitutional Si on a Ga site with substitutional N on an adjacent As site (Si_(Ga)N_(As))~q, where q is the charge state of the defect complex, and (b) Si and N atoms forming a split-interstitial defect on an As site (SiN)~q_(As). All the localized mode frequencies for both defect structures are calculated in the relevant charge states. We have also calculated the formation energy of the (Si_(Ga)N_(As))~q defect as a function of SiN separation, finding that the configuration with the Si on a second-nearest- neighbor Ga site is more favorable in the positive charge state than the configuration with the Si on a nearest-neighbor Ga site to the N atom.