Propriedades estruturais, densidade de deslocações e analise de defeitos superficiais em heteroestruturas semicondutoras por difração multipla de raios-x

AUTOR(ES)
DATA DE PUBLICAÇÃO

1994

RESUMO

In this work. the potential of the X-Ray Multiple Diffraction (MD) technique in studying the heterostructures and semiconductor substrates is investigated. The three-beam (incident, primary and secondary) MD with the secondary parallel to the surface. is the main tool for this investigation. The occurrence of the two types of hybrid reflections in heterostructures. involving the scattering sequences substrate-layer (SL) and layer-substrate (LS). is used to develop a new method of characterizing these structures. The MD theory in mosaic crystals is extended in order to take into account the hybrid reflections occurrence. A computer program to simulate the position and profile of the expected and hybrid MD peaks was developed and it provides informations on: the crystalline perfection (mosaic spread) of the layer and substrate lattices. the tilt and relative misorientation between these lattices and. on the lattice mismatch in the direction parallel (dislocation density) to the interface. GaAs/Si(001) samples with several thicknesses were analyzed. The SL hybrid reflections are used in the analysis of the thick layer samples (600 to 2800 nm) while the LS ones are used just to analyze thin buffer layers (50 nm). Different dislocation densities and stress states (tensile or compressive) in thin and thick layers can be obtained from the LS measurements. The adhesion in the interfaces layer/buffer and buffer/substrate is also investigated from the MD hybrid measurements. A new method based on the two-dimensional mapping of the MD peak profile was developed to assess the crystalline perfection on the semiconductor surface as a function of its finishing. A proposed quasi-perfect crystal model. between the ideally imperfect and the highly perfect crystal, appears in the light of the results. The method allows to observe that the mechanic-chemical polishing applied to the GaAs(001) substrate surface finishing increases the sample mosaic spread in the surface plane. It also shows that for mechanic polished Ge(001) samples. the peak profile is similar to the one simulated with the ideally imperfect crystal model. After the chemical polishing the quasi-perfect crystal model has to be used in order to explain the obtained profile

ASSUNTO(S)

raios x - difração semicondutores cristais

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