Study of defects in conformal GaAs/Si layers by optical techniques and photoetching

We present the characterization of crystal defects in GaAs layers grown on silicon substrates by the conformal growth method. This technique consists of GaAs lateral growth from GaAs seeds confined in between the Si substrate and an overhanging dielectric cap layer. These conformal layers grow with a reduced density of crystal defects, e.g. dislocations, which are effectively filtered by the particular geometrical configuration. The samples were analyzed by micro-Raman spectroscopy, cathodoluminescence, phase stepping microscopy and were etched by diluted stirl solution applied with light (DSL). Several structures were revealed and analyzed, e.g. a quasi-periodic array of hillocks and valleys that are spatially correlated with fluctuations of the luminescence intensity. Other revealed crystal defects were grooves, hillocks and cracks. The main properties of these defects and their possible origin are studied.