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V-shaped defects in InGaN/GaN multiquantum wells
InGaN/GaN multiquantum well (MQW) structures have been grown on (0001) sapphire substrate by metalorganic chemical vapor deposition. From cross-sectional transmission electron microscopy (TEM), a number of V-shaped defects has been observed on the surface which are associated with mixed or pure-edge screw dislocations, as well as with inversion domains. Atomic force microscopy (AFM) reveals that these are hexagonal pits with a width of about 70 nm. The mechanism of formation of these defects has been discussed in terms of stress induced by lattice mismatch and reduced In incorporation on the {101̄1} planes in comparison to the (0001) surface. A decrease in In concentration and also in well thickness during growth has been found. No optical emission has been observed from these defects by cathodoluminescence (CL) studies.
Source:Materials Letters
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