Unexpected Dominance of Vertical Dislocations in High‐Misfit Ge/Si(001) Films and Their Elimination by Deep Substrate Patterning

Marzegalli, Anna; Isa, Fabio; Groiß, Heiko; Müller, E.; Falub, C.V.; Taboada, A. G.; Niedermann, Philippe; Isella, Giovanni; Schäffler, F.; Montalenti, Francesco; Känel, H. von; Miglio, Leo

doi:10.1002/adma.201300550

Cited by 57 publications

(59 citation statements)

References 24 publications

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“…To this end, is necessary to form the coalesced film from a set of Ge pillars featuring fully pyramidal top faceting, as found for narrow Si pillars and higher growth temperature shown in Figure 2. In refs [7], [9] and [10] we indeed demonstrated that no threading-dislocations are present in the upper part of the crystals, where the merging induced by annealing begins. Any additional dislocations nucleating during coalescence would therefore have to reside in a cylindrical expanding bridge, which is still surrounded by free surfaces.…”

Section: Phase-field Simulationsmentioning

confidence: 58%

Engineered Coalescence by Annealing 3D Ge Microstructures into High-Quality Suspended Layers on Si

Salvalaglio

Bergamaschini

Isa

et al. 2015

ACS Appl. Mater. Interfaces

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The move from dimensional to functional scaling in microelectronics has led to renewed interest toward integration of Ge on Si. In this work, simulation-driven experiments leading to high-quality suspended Ge films on Si pillars are reported. Starting from an array of micrometric Ge crystals, the film is obtained by exploiting their temperature-driven coalescence across nanometric gaps. The merging process is simulated by means of a suitable surface-diffusion model within a phase-field approach. The successful comparison between experimental and simulated data demonstrates that the morphological evolution is driven purely by the lowering of surface-curvature gradients. This allows for fine control over the final morphology to be attained. At fixed annealing time and temperature, perfectly merged films are obtained from Ge crystals grown at low temperature (450 °C), whereas some void regions still persist for crystals grown at higher temperature (500 °C) due to their different initial morphology. The latter condition, however, looks very promising for possible applications. Indeed, scanning tunneling electron microscopy and high-resolution transmission electron microscopy analyses show that, at least during the first stages of merging, the developing film is free from threading dislocations. The present findings, thus, introduce a promising path to integrate Ge layers on Si with a low dislocation density.

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Section: Phase-field Simulationsmentioning

confidence: 58%

Engineered Coalescence by Annealing 3D Ge Microstructures into High-Quality Suspended Layers on Si

Salvalaglio

Bergamaschini

Isa

et al. 2015

ACS Appl. Mater. Interfaces

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“…Subsequent material deposition eventually yields a region of the crystal that is completely free from dislocations, although no annealing was performed. 16,18,19 Such an approach has been shown to…”

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confidence: 99%

Disentangling nonradiative recombination processes in Ge micro-crystals on Si substrates

Pezzoli

Giorgioni

Gallacher

et al. 2016

Applied Physics Letters

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We address nonradiative recombination pathways by leveraging surface passivation and dislocation management in µm-scale arrays of Ge crystals grown on deeply patterned Si substrates. The time decay photoluminescence (PL) at cryogenic temperatures discloses carrier lifetimes approaching 45 ns in band-gap engineered Ge micro-crystals. This investigation provides compelling information about the competitive interplay between the radiative band-edge transitions and the trapping of carriers by dislocations and free surfaces. Furthermore, an in-depth analysis of the temperature dependence of the PL, combined with capacitance data and finite difference time domain modeling, demonstrates the effectiveness of GeO2 in passivating the surface of Ge and thus in enhancing the room temperature PL emission.

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“…As already widely reported in the literature, the epitaxial growth of wurtzite GaN on planar 6−11 and patterned 12,13 Si(1 1 1) substrates is favored by the 3-fold surface symmetry, compared to the 4-fold surface symmetry of Si(0 0 1). 14 Additionally, the use of deeply patterned substrates with faceted features at the micrometersize scale would be beneficial for reducing the density of dislocations, 15,16 as well as for improving the light extraction efficiency 17−19 and directionality 20,21 in GaN-based lightemitting diodes. These issues call for the analysis of GaN nucleation and growth on high-index Si surfaces, e.g., {1 1 3} and {15 3 23}, which is a challenging task not widely investigated so far.…”

Section: ■ Introductionmentioning

confidence: 99%

Integration of GaN Crystals on Micropatterned Si(0 0 1) Substrates by Plasma-Assisted Molecular Beam Epitaxy

Isa

Chèze

Siekacz

et al. 2015

Crystal Growth & Design

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We present an innovative approach to integrate arrays of isolated, strainfree GaN crystals on patterned Si substrates. First, micrometer-sized pillars are patterned onto Si(0 0 1) substrates. Subsequently, 2.5 μm Si substrates are deposited by low-energy plasma-enhanced chemical vapor deposition, forming crystals mostly bounded by {1 1 1}, {1 1 3}, and {15 3 23} facets. Plasma-assisted molecular beam epitaxy is then used for GaN deposition. GaN crystals with slanted {0 0 0 1} facets having a root-mean-square surface roughness of 0.7 nm are obtained for a deposited material thickness of >3 μm. Microphotoluminescence measurements performed at room and cryogenic temperature show no yellow luminescence and a neutral donorbound A exciton transition at 3.471 eV (10 K) with a full width at half-maximum of 10 meV. Microphotoluminescence and micro-Raman spectra reveal that GaN grown on Si pillars is strain-free. Our results indicate that the shape of GaN crystals can be tuned by the pattern periodicity and that a reduction of threading dislocations is achieved in their top part.

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Unexpected Dominance of Vertical Dislocations in High‐Misfit Ge/Si(001) Films and Their Elimination by Deep Substrate Patterning

Cited by 57 publications

References 24 publications

Engineered Coalescence by Annealing 3D Ge Microstructures into High-Quality Suspended Layers on Si

Engineered Coalescence by Annealing 3D Ge Microstructures into High-Quality Suspended Layers on Si

Disentangling nonradiative recombination processes in Ge micro-crystals on Si substrates

Integration of GaN Crystals on Micropatterned Si(0 0 1) Substrates by Plasma-Assisted Molecular Beam Epitaxy

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