Characterization of Ga_1−xMn_xAs/(001)GaAs epilayers grown by low-temperature molecular beam epitaxy

Abstract

Ga_{1− x} Mn _x As/(001) GaAs (x = 2.2, 5.6, 9 at.%) epitaxial layers grown by low-temperature MBE, exhibiting anisotropic magnetic properties, have been characterized using a range of transmission electron microscopy techniques and secondary-ion mass spectrometry. Banded contrast features on inclined planes are observed for the [110] projection of micron-thick samples with high Mn content, and are attributed to a compositional fluctuation in the interstitial Mn content. Precipitates attributed to tetragonally distorted MnAs are associated with the onset of stacking-fault formation during layer growth. The formation of an Mn–O layer at the surface of the samples is also observed, attributed to post-growth oxidation of an Mn surfactant layer.

Acknowledgements

The authors are grateful to Professor Cullis, Dr Ian Ross and Mr Alan Walker of the University of Sheffield for the use of the Jeol 2010f electron microscope. The authors would like to acknowledge the contributions of B. Ja Ber and A.P. Kovarsky for the SIMS studies, and Frank Glas for useful discussions on the 002 dark-field imaging technique. This work was supported under EPSRC contract GR/S25630/01 and GR/R46465.