Isotopic heterostructures of the form, Ga14N/Ga15N/Ga14N, were used to study N self-diffusion by means of secondary-ion mass spectrometry and thermally activated decomposition techniques. The diffusion profiles were measured after interdiffusion of the Ga14N and Ga15N layers at temperatures of between 770 and 970C. It was noted that such isotopic heterostructures were especially suitable for self-diffusion studies because diffusion took place at interfaces within the GaN crystal, and was therefore free from interfering effects such as surface electric fields, mechanical stresses or chemical potential gradients. It was found that the temperature dependence of N self-diffusion in the hexagonal phase could be described by:

D (cm2/s) = 1600 exp[-4.1(eV)/kT]

and by an entropy, for self-diffusion, of about 10k.

O.Ambacher, F.Freudenberg, R.Dimitrov, H.Angerer, M.Stutzmann: Japanese Journal of Applied Physics - 1, 1998, 37[5A], 2416-21