An investigation was made of the concentrations and distributions of point defects in GaMnAs, grown by low-temperature molecular-beam epitaxy, using ultra-high vacuum cross-sectional scanning tunneling microscopy. High-resolution constant-current microscopy revealed so-called A, M and V defects; associated with AsGa, MnGa and VAs, respectively. The A and V defects were present in all low-temperature grown layers, while M defects were located predominantly within the GaMnAs layers. In these layers, the concentration of V defects ([V]) increased with the concentration of M defects ([M]); consistent with a Fermi-level dependent vacancy formation energy. Furthermore, [M] was typically 2 to 3 times the magnitude of [A] or [V]; suggesting a significant compensation of the free carriers associated with MnGa. A quantitative defect pair correlation analysis revealed clustering of nearest V–V pairs and anti-clustering of nearest M–M, M–V, and M–A pairs. For all pair separations greater than 2nm, random distributions of defects were apparent.

Nanometer-Scale Studies of Point Defect Distributions in GaMnAs Alloys. J.N.Gleason, M.E.Hjelmstad, V.D.Dasika, R.S.Goldman, S.Fathpour, S.Charkrabarti, P.K.Bhattacharya: Applied Physics Letters, 2005, 86[1], 011911 (3pp)