An investigation was made of the effect of film thickness upon the distribution of Mn atoms at various lattice sites in Ga1–xMnxAs thin films. It was found that the growth surface acted as a sink which facilitated the out-diffusion of Mn interstitials (Mni), and thus reduced their concentration in the film. The out-diffused Mni accumulated on the surface in a surface oxide layer and did not participate in the ferromagnetism of the film. For thin films less than 15nm thick, no Mni could be detected. Because of the absence of compensating Mni defects, higher Tc values could be achieved for such extremely thin Ga1–xMnxAs layers. These results agreed with a previously suggested Fermi-level governed upper limit on the Tc of III–Mn–V ferromagnetic semiconductors.

Effect of Film Thickness on the Incorporation of Mn Interstitials in Ga1–xMnxAs. K.M.Yu, W.Walukiewicz, T.Wojtowicz, J.Denlinger, M.A.Scarpulla, X.Liu, J.K.Furdyna: Applied Physics Letters, 2005, 86[4], 042102 (3pp)