Strain relaxation of GaAs/Ge crystals on patterned Si substrates

Taboada, A. G.; Kreiliger, Thomas; Falub, C.V.; Isa, Fabio; Salvalaglio, Marco; Wewior, Lukasz Jakub; Fuster, David; Richter, M.; Uccelli, Emanuele; Niedermann, Philippe; Neels, Antonia; Mancarella, F.; Alén, Benito; Miglio, Leo; Dommann, Alex; Isella, Giovanni; Känel, H. von

doi:10.1063/1.4861864

Cited by 25 publications

(18 citation statements)

References 28 publications

(34 reference statements)

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“…Thirdly, no experimental evidence exists concerning the possible presence of impurities, with the exception of Mg involved in the intentional doping. Fourthly, other effects such as strain [73–74] can influence the electronic level structure of the nanowires. From our results, in the case of the growth on the GaAs(111)B substrate, the estimated activation energy ( E x ) for the release of the less bound charge carrier in the radiative state is far from the ionization energy (28 meV) reported for Mg in the literature [41].…”

Section: Discussionmentioning

confidence: 99%

Substrate and Mg doping effects in GaAs nanowires

Kannappan¹,

Sédrine²,

Teixeira³

et al. 2017

Beilstein J. Nanotechnol.

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Mg doping of GaAs nanowires has been established as a viable alternative to Be doping in order to achieve p-type electrical conductivity. Although reports on the optical properties are available, few reports exist about the physical properties of intermediate-to-high Mg doping in GaAs nanowires grown by molecular beam epitaxy (MBE) on GaAs(111)B and Si(111) substrates. In this work, we address this topic and present further understanding on the fundamental aspects. As the Mg doping was increased, structural and optical investigations revealed: i) a lower influence of the polytypic nature of the GaAs nanowires on their electronic structure; ii) a considerable reduction of the density of vertical nanowires, which is almost null for growth on Si(111); iii) the occurrence of a higher WZ phase fraction, in particular for growth on Si(111); iv) an increase of the activation energy to release the less bound carrier in the radiative state from nanowires grown on GaAs(111)B; and v) a higher influence of defects on the activation of nonradiative de-excitation channels in the case of nanowires only grown on Si(111). Back-gate field effect transistors were fabricated with individual nanowires and the p-type electrical conductivity was measured with free hole concentration ranging from 2.7 × 1016 cm−3 to 1.4 × 1017 cm−3. The estimated electrical mobility was in the range ≈0.3–39 cm2 /Vs and the dominant scattering mechanism is ascribed to the WZ/ZB interfaces. Electrical and optical measurements showed a lower influence of the polytypic structure of the nanowires on their electronic structure. The involvement of Mg in one of the radiative transitions observed for growth on the Si(111) substrate is suggested.

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Section: Discussionmentioning

confidence: 99%

Substrate and Mg doping effects in GaAs nanowires

Kannappan¹,

Sédrine²,

Teixeira³

et al. 2017

Beilstein J. Nanotechnol.

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“…[13][14][15] Therefore, the pyramidal morphology of the GaAs depends on the size of the Si pillar as evidenced from the top view SEM images (Figures 1(c)-1(h)). A detailed description of the morphology can be found in the work of Taboada et al 2 B. Photoluminescence Figure 2 shows the low temperature PL spectra measured by exciting the central area of the top (001) surface of the GaAs/Ge crystals on differently sized Si pillars. The peak centered at $1.5 eV stems from recombination in the GaAs, whereas the distinct peak on the lower energy side is attributed to emission from the InGaAs QW.…”

Section: A Electon Micrographsmentioning

confidence: 99%

“…Since Ge and GaAs are almost lattice matched (0.08% mismatch at 300 K) and only slightly differ in thermal expansion, low defect GaAs can be obtained by overgrowing these Ge crystals. 2 …”

mentioning

confidence: 97%

“…Thus, combining the benefits of both materials would pave the way for the monolithic integration of GaAs elements like quantum emitters and optical switches with Si integrated circuits featuring future multifunctional semiconductor devices. 1,2 However, this heteroepitaxial integration is complicated by several issues, most notably the large lattice and thermal mismatch of the materials in question (4.1% and 120%, respectively, for GaAs on Si at 300 K). 2 Plastic strain relaxation by dislocations is therefore inevitable when GaAs beyond some critical thickness is grown onto Si.…”

mentioning

confidence: 99%

“…1,2 However, this heteroepitaxial integration is complicated by several issues, most notably the large lattice and thermal mismatch of the materials in question (4.1% and 120%, respectively, for GaAs on Si at 300 K). 2 Plastic strain relaxation by dislocations is therefore inevitable when GaAs beyond some critical thickness is grown onto Si. For layer thickness above a few microns, wafer bowing and crack formation may become additional obstacles.…”

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confidence: 99%

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Heterointegration of InGaAs/GaAs quantum wells on micro-patterned Si substrates

Jung

Taboada

Stumpf

et al. 2015

Journal of Applied Physics

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InGaAs/GaAs quantum wells (QWs) grown on μ-patterned Ge/Si substrates by metal organic vapor phase epitaxy are investigated by electron microscopy and spatially resolved photoluminescence (PL) spectroscopy. The lattice parameter mismatch of GaAs and Si is overcome by a Ge buffer layer grown by low-energy plasma enhanced chemical vapor deposition. The GaAs crystals form truncated pyramids whose shape is strongly affected by the geometry of the underlying pattern consisting of 8 μm deep and 3–50 μm wide square Si pillars. Comparing the measured PL energies with calculations performed in the effective mass approximation reveals that the QW emission energies are significantly influenced by the GaAs morphology. It is shown that the geometry favors indium diffusion during growth from the inclined facets towards the top (001) facet. The Si pillar-size dependent release of thermally induced strain observed in the PL measurements is confirmed by X-ray diffraction.

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Strain relaxation in Ge microcrystals studied by high‐resolution X‐ray diffraction

Rozbořil

Meduňa

Falub

et al. 2015

Physica Status Solidi (a)

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Deposition on patterned substrates is a promising method for obtaining high quality, strain and defect free heteroepitaxial layers. In this paper we investigate the crystalline structure of quasi-continuous Ge layers consisting of closely spaced microcrystals on a Si substrate patterned in the form of a regular net of lithographically defined squared based pillars. Lattice parameters, strain and degree of relaxation of the Ge microcrystals are measured by standard high-resolution X-ray diffraction using reciprocal space mapping. In particular, we focus on the impact of Si pillar size and spacing on the Ge crystal quality by analyzing how the bending of crystal lattice planes caused by thermal stress relaxation and random crystal tilts affect the width of the diffraction peaks.

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Strain relaxation of GaAs/Ge crystals on patterned Si substrates

Cited by 25 publications

References 28 publications

Substrate and Mg doping effects in GaAs nanowires

Substrate and Mg doping effects in GaAs nanowires

Heterointegration of InGaAs/GaAs quantum wells on micro-patterned Si substrates

Strain relaxation in Ge microcrystals studied by high‐resolution X‐ray diffraction

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