An investigation was made, of the possibility of enhanced diffusion, using quantum-well probe structures. It was found that deeper quantum wells (75- and 100nm-deep) exhibited a steady decrease in relative photoluminescence intensity with time. This furnished evidence for the cooperative effects of channelling and defect diffusion in deep-etch damage propagation. However, shallow quantum wells (15 or 25nm from the surface) exhibited a slight decrease, followed by a gradual increase, in relative photoluminescence intensity with time. This was attributed to defect annihilation. Exposure to above-bandgap illumination, as used to simulate and enhance carrier generation during etching, appeared to accelerate defect annihilation in high defect-concentration regions and resulted in an increase in quantum-well luminescence. In lower defect-concentration areas, above-bandgap illumination did not appear to alter quantum-well luminescence significantly. This difference in behavior was attributed to a difference in diffusion constant. It was noted that the diffusion constant in less-damaged regions could be much lower than that in highly damaged material.

Enhanced Diffusion as a Mechanism for Ion-Induced Damage Propagation in GaN. E.D.Haberer, C.H.Chen, M.Hansen, S.Keller, S.P.DenBaars, U.K.Mishra, E.L.Hu: Journal of Vacuum Science and Technology B, 2001, 19[3], 603-8