Current-induced migration of surface adatoms during GaN growth by molecular beam epitaxy

The influence of electric fields on surface migration of Gallium (Ga) and N itrogen (N) adatoms is studied during GaN growth by molecular beam epitaxy (MBE). When a direct current (DC) is used to heat the sample, long distance migration of Ga adatoms and diffusion asymmetry of N adatoms at steps are observed. On the other hand, if an alternating current (AC) is used, no suc h preferential adatom migration is found. This effect is attributed to the effective positive charges of surface adatoms. representing an effect of el ectro-migration. The implications of such current-induced surface migration to GaN epitaxy are subsequently investigated. It is seen to firstly change the distribution of Ga adatoms on a growing surface, and thus make the gro wth to be Ga-limited at one side of the sample but N-limited at the other s ide. This leads to different optical qualities of the film and different mo rphologies of the surface. (C) 2001 Elsevier Science B.V. All rights reserv ed.