Atomically ordered (Mn,Ga)As crystallites on and within GaAs Dedicated to Professor Joachim Bohm on the occasion of his 80 th birthday

• Published in: Crystal research and technology (1979) Vol. 50; no. 12; pp. 967 - 973
• Main Authors: Häusler, Ines, Moeck, Peter, Volz, Kerstin, Neumann, Wolfgang
• Format: Journal Article
• Language: English
• Published: 01.12.2015
• ISSN: 0232-1300; 1521-4079
• DOI: 10.1002/crat.201500310

Metal organic vapor phase epitaxy (MOVPE) of Mn‐rich (Mn,Ga)As on (001) oriented GaAs wafers resulted in atomically ordered (Mn,Ga)As crystallites of two morphological kinds, partially embedded on the wafer surface and fully embedded within the single crystalline matrix. While the former were apparently free of defects (other than unavoidable point defects), the latter contained two domains separated by a grain boundary. Since atomic ordering can be modeled by space group symmetry descent considerations (Bärnighausen trees) that start with the space group of the known crystallographic phases of random (Mn,Ga)As alloys with specified chemical compositions, reasonable structure hypotheses have been derived for two atomically ordered Mn 0.75 Ga 0.25 As phases that we call the trigonal α' and the monoclinic β' phases. The implications of these structure hypotheses are in agreement with the results of a range of scanning transmission electron microscopy (STEM) and parallel illumination electron diffraction (ED) studies that include quantitative energy dispersive X‐ray spectroscopy, X‐ray spectroscopic imaging, as well nanobeam diffraction and high angle precession ED. The coexistence of two domains within the fully embedded crystallites is predicted by the corresponding Bärnighausen tree and observed experimentally for the fully embedded crystallites.