Structure and recombination in InGaAs/GaAs heterostructures

Abstract

X 10-3) epilayers on GaAs was studied with scanning cathodoluminescence (CL), transmission electron microscopy (TEM), high-voltage electron microscopy, and scanning electron microscopy. CL shows that nonradiative recombination lines exist in the GaAs buffer layer as far as 4000 A from the interface. The density of these defects is independent of substrate dislocation density. Plan-view TEM analysis indicates that the majority of these dislocations in the buffer layer are sessile edge half-loops. Cross-sectional TEM shows that loops also extend into the InGaAs epilayer, but the majority ofthe loops are located on the buffer layer (substrate) side of the interface, A mode! is proposed to explain sessile edge dislocation formation in the buffer layer. A comparison of CL and high-voltage electron microscopy images from the same interface area reveals that the dark nonradiative recombination lines seen in scanning luminescence images in this high misfit system do not correspond to the normal, isolated misfit dislocation. The nonradiative recombination line spacing is 3 p.m, whereas the interface dislocation spacing is 400-1000 A. It is shown that the nonradiative recombination lines observed in CL of the interface correspond to specific groups of dislocations with different TEM contrast behavior. The dark nonradiative recombination lines also correlate with asymmetric surface ridges, suggesting that they introduce preferred nucleation sites, and that these effects are different for the two (110) directions.

Misfit Dislocations in Epitaxial Heterostructures: Mechanisms of Generation and Multiplication

“…1c, d) have been studied in detail in SiGe/Si [3,4] and InGaAs/GaAs [1,2] heterostructures. The major features of such networks are as follows: (i) multilevel MD network at the interface; (ii) misfit dislocation pile-ups spreading deeply into the substrate; (iii) low density of threading dislocations in the layer.…”

“…That result required new mechanisms to be proposed to explain the generation of dislocation half-loops in low misfit (f`1%) heterostructures [7,8]. In InGaAs/GaAs [1] and SiGe/Si [9] heterostructures, it has been found that tips of dislocation angles, formed at the crossing points of MDs with identical Burgers vector, turned down into the substrate rather than into the layer. It leads to the conclusion that the Hagen-Strunk mechanism [10] is not valid for at least these heterostructures.…”

“…The attention was paid to the effect of plastic deformation of the substrate during epitaxial growth. Appropriate dislocation patterns (hereafter called three-dimensional misfit dislocation (MD) networks) were observed, for example, in InGaAs/GaAs [1,2], SiGe/Si [3,4] and SiGe/Ge [5] heterostructures. The formation of such 3D-MD networks was attributed to the MD multiplication and/or dislocation interaction.…”

Elemental Dislocation Mechanisms Involved in the Relaxation of Heteroepitaxial Semiconducting Systems

“…The interaction between developed misfit dislocations are very numerous and principally observed in high misfit systems. They result in more or less complex configurations involving often Lomer Cottrell locks (edge dislocations) in the substrate [30,31].…”

Estudio de capas de desacoplo de InGaAs/GaAs(001) por crecimiento combinado de MBE-ALMBE en forma dinámica y escalonada

“…Esto corrobora la hipótesis de la escalada por difusión de vacantes de Ga, ya que al no ser químicamente equivalentes los núcleos de las dislocaciones perpendiculares que aparecen en el plano (001) del sistema InGaAs/GaAs, la difusión de vacantes de un solo tipo de átomo favorecerá el movimiento por escalada de un solo tipo de dislocaciones. En las CD, sin embargo, las dislocaciones de Lomer encontradas son diferentes, ya que aparecen en dos direcciones y en fragmentos más cortos, por lo que quizá en este caso sí se hayan formado por el mecanismo de reacción de Fitgerald (1).…”