GROWTH OF HIGH-QUALITY RELAXED IN0.3GA0.7AS GAAS SUPERLATTICES/

With a low strained InxGa1-xAs/GaAs(x similar to 0.01) superlattice (S L) buffer layer, the crystal quality of 50 period relaxed In0.3Ga0.7As /GaAs strained SLs has been greatly improved and over 13 satellite pea ks are observed from X-ray double-crystal diffraction, compared with t hree peaks in the sample without the buffer layer. Cross-section trans mission electron microscopy reveals that the dislocations due to super lattice strain relaxation are blocked by the SLs itself and are buried into the buffer layer. The role of the SL buffer layer lies in that t he number of the dislocations is reduced in two ways: (1) the island f ormation is avoided and (2) the initial nucleation of the threading di slocations is retarded by the high-quality growth of the SL buffer lay er. When the dislocation pinning becomes weak as a result of the reduc ed dislocation density, the SLs can effectively move the threading dis locations to the edge of the wafer.