Experimental results for wurtzite epitaxial GaN layers grown on sapphire and SiC

substrates were presented. Using a set of samples having differing values of

residual strain, it was demonstrated that the high dislocation density enhanced the

spin relaxation rate via the Elliott–Yafet mechanism. This was confirmed by a T−1 temperature dependence of the spin-relaxation times. The influence of the valenceband

structure upon the hole-spin relaxation was also highlighted. In particular, a

decrease in the hole-spin relaxation rate, accompanied by a strong polarization rate

(~50%) of the differential reflectivity signal (ΔR/R), was observed when the

splitting ΔEAB between the heavy-hole and the light-hole bands was larger than the

broadening ΓA of the A excitonic transition. On the other hand, the overlap of the A

and B resonances for ΓA>ΔEAB was responsible for a decrease in the ΔR/R

polarization rate (~10%) and an enhancement of the spin relaxation rate.

Dislocation Density and Band Structure Effects on Spin Dynamics in GaN.

C.Brimont, M.Gallart, A.Gadalla, O.Crégut, B.Hönerlage, P.Gilliot: Journal of

Applied Physics, 2009, 105[2], 023502