Characterisation of intrinsic and compensated defect microstructures in dilute III-V-N alloys

摘要

A comprehensive analysis of the Fourier transform infrared (FTIR) absorption and Raman scattering data on impurity modes is reported for the technologically important dilute ternary GaAs{sub}(1-x)N{sub}x, and GaP{sub}(1-x)N{sub}x (x<0.03) alloys grown on GaAs and GaP, respectively, by metal organic chemical vapour deposition (MOCVD) and solid source molecular beam epitaxy (MBE). For low nitrogen concentrations in GaAs{sub}(1-x)N{sub}x [GaP{sub}(1-x)N{sub}x] (i.e. x<0.015), most of the N atoms occupy the As [P] sublattice N{sub}(As) [N{sub}P]. They prefer, however, to move out of their substitutional sites to more energetically favourable locations at higher x values. To comprehend the large width of the localised vibrational mode (LVM) in GaAs{sub}(1-x)N{sub}x near 470cm{sup}(-1), the possibilities of Ga isotopes (69{sup left}Ga and 71{sup left}Ga) and/or intrinsic defects participating with N{sub}(As) in different configurations were studied. Theoretical results for the N-local modes and its isotopic shifts are found in good agreement with the FTIR data. Although, the presence of isolated N-interstitials. (N{sub}(int)) in GaAs{sub}(1-x)N{sub}x is quite unlikely at higher compositions (0.03 >x>0.015), the formations of nonradiative complex microstructures involving N and/or intrinsic defects are energetically favourable. The impurity modes for such complex centres were predicted and the possibility of observing them by optical spectroscopy was evaluated.