Growth of high-quality relaxed In0.3Ga0.7As/GaAs superlattices

Abstract

Abstract With a low strained In x Ga 1− x As/GaAs( x ∼ 0.01) superlattice (SL) buffer layer, the crystal quality of 50 period relaxed In 0.3 Ga 0.7 As/GaAs strained SLs has been greatly improved and over 13 satellite peaks are observed from X-ray double-crystal diffraction, compared with three peaks in the sample without the buffer layer. Cross-section transmission electron microscopy reveals that the dislocations due to superlattice 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 the number of the dislocations is reduced in two ways: (1) the island formation is avoided and (2) the initial nucleation of the threading dislocations is retarded by the high-quality growth of the SL buffer layer. When the dislocation pinning becomes weak as a result of the reduced dislocation density, the SLs can effectively move the threading dislocations to the edge of the wafer.