A complex x-ray structure characterization of Ge thin film heterostructures integrated on Si(001) by aspect ratio trapping and epitaxial lateral overgrowth selective chemical vapor deposition techniques

摘要

The development of Ge thin film substrates with low defect densities is of interest for future microelectronics as well as photovoltaics. This paper presents a complex x-ray characterization of Ge heterostructures, which were integrated on patterned Si(001) substrates using "aspect ratio trapping (ART)" and "epitaxial lateral overgrowth (ELO)." In both cases, thermal SiO_2 layers were patterned into trenches with appropriate aspect ratio to confine misfit dislocations. In the case of ART Ge thin films grown in 180 nm spaced trenches, the x-ray characterization reveals that the Ge coalescence process between neighboring growth windows must be carefully controlled to avoid defect generation. In the case of ELO Ge heterostructures grown from trenches spaced by 20 μm, coalescence effects are clearly reduced but complications are detected in the form of lattice plane tilt in the ELO wings. Simulations are applied to unveil the influence of the different thermal expansion coefficients of Ge, Si, and SiO_2 on the strain status of the ART and ELO Ge heterostructures.