Recombination of Shockley partial dislocations by electron beam irradiation in wurtzite GaN

Dissociated a-type screw dislocations in gallium nitride, comprising pairs of 30° Shockley partial dislocations separated by I2 basal stacking faults, were observed by aberration-corrected high resolution transmission electron microscopy (HRTEM). HRTEM image simulations, in conjunction with density functional theory calculations, led to the identification of the core structures of the Shockley partials. Both partials were found to belong to the glide set rather than the shuffle one, while the core with gallium polarity is reconstructed, but the one with nitrogen polarity is not. During in situ irradiation by the electron beam, the I2 stacking fault ribbon was found to shrink, ultimately leading to a remerging of the two partials. This reversal of the dissociation reaction was attributed to recombination enhanced dislocation glide, whereby the Shockley partial with nitrogen polarity was identified to be the mobile one. A possible model explaining this mobility is proposed comprising a local modification of the dislocation's electronic structure due to the presence of nitrogen vacancies at its core.Dissociated a-type screw dislocations in gallium nitride, comprising pairs of 30° Shockley partial dislocations separated by I2 basal stacking faults, were observed by aberration-corrected high resolution transmission electron microscopy (HRTEM). HRTEM image simulations, in conjunction with density functional theory calculations, led to the identification of the core structures of the Shockley partials. Both partials were found to belong to the glide set rather than the shuffle one, while the core with gallium polarity is reconstructed, but the one with nitrogen polarity is not. During in situ irradiation by the electron beam, the I2 stacking fault ribbon was found to shrink, ultimately leading to a remerging of the two partials. This reversal of the dissociation reaction was attributed to recombination enhanced dislocation glide, whereby the Shockley partial with nitrogen polarity was identified to be the mobile one. A possible model explaining this mobility is proposed comprising a local modification of...