SURFACE RELAXATION OF STRAINED HETEROSTRUCTURES REVEALED BY BRAGG LINE SPLITTING IN LACBED PATTERNS

Bragg line splitting near the shadow image of a thin strained InGaAs l ayer, buried in GaAs and without strain relief by misfit dislocations, was found in large angle convergent beam electron diffraction (LACBED ) patterns of cross-section specimens. The surface relaxation of the b uilt-in strain and the Bragg line intensities were calculated. A quali tative agreement between the experimental Bragg line splitting and the theoretical calculations is demonstrated. Closer matching was achieve d using a ''line-force'' model of the surface relaxation, whereas a Fo urier transform solution showed significant underestimation of the Bra gg line splitting. The possibility of characterising the built-in stra in in thin strained layers, by measuring this Bragg line splitting in LACBED patterns, has been explored.