ZnSe Molecular Beam Epitaxial Growth on Charge-Balanced GaAs Surfaces

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ZnSe related II-VI widegap semiconductors are promising materials for optoelectronic devices. In order to obtain ideal ZnSe/GaAs interfaces without the charge imbalance, we have investigated ZnSe epitaxial layers grown by molecular beam epitaxy on vicinal GaAs (110) substrates using reflection high-energy electron diffraction (RHEED), atomic force microscopy (AFM), photoluminescence (PL), transmission electron microscopy, high-resolution X-ray diffraction, and PL topography.ZnSe films on vicinal GaAs (110) surfaces misoriented 6° toward (111) A show poor crystal quality and rough surface morphology with (111) facets. On the other hand, RHEED and AFM observations reveal that ZnSe growth proceeds in a layer-by-layer fashion on vicinal GaAs (110) surfaces misoriented 6° toward (111) B and that the surfaces consist of regular arrays of monoatomic steps. The PL spectra are dominated by the near-band-edge emission. However, characteristic structures of stacking faults and high density of threading dislocations are observed. We successfully decreased these stacking faults and threading dislocations lower than two or three orders by incorporating GaAs buffer layers. ZnSe (110) films with high-quality and flat interfaces are coherently grown on vicinal GaAs (110) surfaces misoriented 6° towards (111) B with GaAs buffer layers.