Re fe ren ces Ac knowl edge ments PE RI ODIC MOD U LA TION OF STRAIN FIELDS AND MAGENTIC ANI SO TROPY IN (Ga,Mn)As/InAs/GaAs STRUC TURES
A Lugstein, An, M Steinmair, Y Hyun, E Bertagnolli, M Weil, P Ponratz, M Schramböck, T Roch, G Strasser, P Detz, A Klang
(+15 others)
2010
355306 of Crys tal Growth
unpublished
Thin lay ers of (Ga,Mn)As mag netic semi con duc tor ex hibit mag netic ani so tropy which is strongly in flu enced by lattice match ing strains in tro duced into these lay ers dur ing epitaxial growth. Lat er ally ho mo ge neous strains can be induced by grow ing these lay ers on top of GaAs (com pres-sive strain) or (In,Ga)As (ten sile strain) buff ers [1]. Litho graphic tech niques can be used to cre ate com pli cated strain pat terns lead ing to spa tially vary ing mag netic ani so-tropy
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... 4]. We com bined e-beam li thog ra phy and dry etch ing with mo lec u lar beam ep i taxy to cre ate or dered fields of InAs quan tum dost on GaAs(001) sub strate which were sub se quently cov ered by a Ga 0.95 Mn 0.05 As cap ping layer. High-res o lu tion X-ray dif frac tion re cip ro cal-space map ping is con ven tion ally used to ex plore the strains in sim i lar cases. How ever, the low growth tem per a ture required to in cor po rate Mn at oms into (Ga,Mn)As lay ers causes that the crys tal qual ity of such heterostructures is often not as good as in the case of con tin u ous epitaxial lay ers and pre vi ously re ported ap proaches to char ac ter ize the strain fields us ing the X-ray data are there fore not di rectly ap pli ca ble. Fur ther com pli ca tions arise from the com bined ef fects of strain and chem i cal rough ness. Here we re port on a sim ple fit ting-free meth od ol ogy to ev i dence the pres ence of pe ri odic strain fields from the mea sured X-ray data and show how kinematical the ory of X-ray scat ter ing cou pled with the so lu tion of elas tic ity equa tions can be used to deter mine the main fea tures of these strain fields. The pro ceed ings are or ga nized as fol lows: first we pres ent the cal cu la tions of the strain fields in the case of (Ga,Mn)As lay ers grown on top of pe ri odic ar rays of InAs quan tum dots. Then we dis cuss the eval u a tion of the in ten-sity pro files along the sat el lites stem ming from lat eral pe ri-od ic ity and we show that the pres ence of strain can be ev i denced from the com par i son of the rel a tive in ten sity of the first pair of sat el lites. Fi nally, we pres ent the re sults of X-ray dif frac tion ex per i ment. The strain in (Ga,Mn)As/InAs/GaAs struc tures orig i-nates in dif fer ent in trin sic lat tice pa ram e ters of the con stit-u ent ma te ri als. We used a com bi na tion of Fou rier and fi nite Fig ure 1. Cal cu lated e xx and e zz com po nents of the strain ten sor in a sam ple con tain ing pe ri odic ar ray of quan tum dots. The dots have the shape of a 10nm high trun cated cone with 40nm bot tom ra dius and 10nm top ra dius and are as sumed to be com posed of pure InAs.
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