2024/10/04 by Christoph Wilflingseder, Johannes Aberl, Wilflingseder, Christoph +25 · 1 citation
Engineering · Materials Science · #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #Photonic and Optical Devices #Semiconductor Lasers and Optical Devices #Silicon Nanostructures and Photoluminescence
paper · pdf · doi:10.48550/arxiv.2410.03295
openalex publication_date 2024/10/04 · openalex created_date 2024/10/31 · openalex updated_date 2026/07/28
Germanium (Ge), the next-in-line group-IV material, bears great potential to add functionality and performance to next-generation nanoelectronics and solid-state quantum transport based on silicon (Si) technology. Here, we investigate the direct epitaxial growth of two-dimensional high-quality crystalline Ge layers on Si deposited at ultra-low growth temperatures (TGe = 100∘C-350∘C) and pristine growth pressures (\lesssim 10-10 mbar). First, we show that TGe does not degrade the crystal quality of homoepitaxial Ge/Ge(001) by comparing the point defect density using positron annihilation lifetime spectroscopy. Subsequently, we present a systematic investigation of the Ge/Si(001) heteroepitaxy, varying the Ge coverage (θGe, 1, 2, 4, 8, 12, and 16 nm) and TGe (100∘C to 300∘C, in increments of 50∘C) to assess the influence of these parameters on the layer's structural quality. Atomic force microscopy revealed a rippled surface topography with superimposed grainy features and the absence of three-dimensional structures, such as quantum dots. Transmission electron microscopy unveiled pseudomorphic, grains of highly crystalline growth separated by defective domains. Thanks to nanobeam scanning x-ray diffraction measurements, we were able to evidence the lattice strain fluctuations due to the ripple-like structure of the layers. We conclude that the heteroepitaxial strain contributes to the formation of the ripples, which originate from the kinetic limitations of the ultra-low temperatures.