Defects and their reduction in Ge selective epitaxy and coalescence layer on Si with semicylindrical voids on SiO&lt;formula&gt;
                     &lt;tex&gt;$_{2}$&lt;/tex&gt;
                  &lt;/formula&gt; masks

Yako, Motoki; Ishikawa, Yasuhiko; Abe, Eiji; Wada, Kazumi

doi:10.1109/jstqe.2018.2846027

Cited by 7 publications

(15 citation statements)

References 30 publications

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“…Regular semielliptical voids are formed at the top of the SiO 2 trenches as a result of the coalescence of the Ge overgrowth [ 30 ]. These voids indicate perfect coalesced Ge layer forms [ 46 , 47 ]. The formation of voids is the critical factor to deplete threading dislocation defects from the SEG Ge layers.…”

Section: Resultsmentioning

confidence: 99%

Dual-Step Selective Homoepitaxy of Ge with Low Defect Density and Modulated Strain Based on Optimized Ge/Si Virtual Substrate

Wang

et al. 2022

Materials

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In this manuscript, a novel dual-step selective epitaxy growth (SEG) of Ge was proposed to significantly decrease the defect density and to create fully strained relaxed Ge on a Si substrate. With the single-step SEG of Ge, the threading defect density (TDD) was successfully decreased from 2.9 × 107 cm−2 in a globally grown Ge layer to 3.2 × 105 cm−2 for a single-step SEG and to 2.84 × 105 cm−2 for the dual-step SEG of the Ge layer. This means that by introducing a single SEG step, the defect density could be reduced by two orders of magnitude, but this reduction could be further decreased by only 11.3% by introducing the second SEG step. The final root mean square (RMS) of the surface roughness was 0.64 nm. The strain has also been modulated along the cross-section of the sample. Tensile strain appears in the first global Ge layer, compressive strain in the single-step Ge layer and fully strain relaxation in the dual-step Ge layer. The material characterization was locally performed at different points by high resolution transmission electron microscopy, while it was globally performed by high resolution X-ray diffraction and photoluminescence.

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Section: Resultsmentioning

confidence: 99%

Dual-Step Selective Homoepitaxy of Ge with Low Defect Density and Modulated Strain Based on Optimized Ge/Si Virtual Substrate

Wang

et al. 2022

Materials

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“…Later, a thicker Ge layer was formed where the lateral overgrowth with a thickness of 700 nm in 180 nm width trenches occurs as shown in Figure 2d-f. As the film thickness increases, Ge continues to grow along (111), (113) crystal plane direction until a continuous Ge layer with flat-top and symmetrical voids formed on the SiO 2 mask as the result of the coalescence of Ge overgrowth in Figure 2e. Previously, some reports have demonstrated the formation of voids on SiO 2 masks when a perfect coalescence is obtained [34,35]. The Ge overgrowth on the SiO 2 surface occurs, and when the layer thickness exceeds a half of the SiO 2 mask width, void formation occurs beneath the coalesced layer.…”

Section: Growth Mechanismmentioning

confidence: 99%

Strain Modulation of Selectively and/or Globally Grown Ge Layers

Wang

Miao

et al. 2021

Nanomaterials

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This article presents a novel method to grow a high-quality compressive-strain Ge epilayer on Si using the selective epitaxial growth (SEG) applying the RPCVD technique. The procedures are composed of a global growth of Ge layer on Si followed by a planarization using CMP as initial process steps. The growth parameters of the Ge layer were carefully optimized and after cycle-annealing treatments, the threading dislocation density (TDD) was reduced to 3 × 107 cm−2. As a result of this process, a tensile strain of 0.25% was induced, whereas the RMS value was as low as 0.81 nm. Later, these substrates were covered by an oxide layer and patterned to create trenches for selective epitaxy growth (SEG) of the Ge layer. In these structures, a type of compressive strain was formed in the SEG Ge top layer. The strain amount was −0.34%; meanwhile, the TDD and RMS surface roughness were 2 × 106 cm−2 and 0.68 nm, respectively. HRXRD and TEM results also verified the existence of compressive strain in selectively grown Ge layer. In contrast to the tensile strained Ge layer (globally grown), enhanced PL intensity by a factor of more than 2 is partially due to the improved material quality. The significantly high PL intensity is attributed to the improved crystalline quality of the selectively grown Ge layer. The change in direct bandgap energy of PL was observed, owing to the compressive strain introduced. Hall measurement shows that a selectively grown Ge layer possesses room temperature hole mobility up to 375 cm2/Vs, which is approximately 3 times larger than that of the Ge (132 cm2/Vs). Our work offers fundamental guidance for the growth of high-quality and compressive strain Ge epilayer on Si for future Ge-based optoelectronics integration applications.

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“…[38][39][40][41] However, there exist several issues such as a significant dopant diffusion/Si-Ge intermixing in the high-temperature annealing and a poor optical coupling between the Ge photodetector and Si optical waveguide in the thick-buffer/ART techniques, as previously described in detail. 42) As an alternative approach, our group has proposed a method utilizing a coalescence of adjacent Ge strips selectively grown on Si covered with an arrayed SiO 2 mask. 42,43) Semicylindrical voids are embedded in the coalesced Ge film over the SiO 2 masks, bending the dislocations in Ge downward to the void surface.…”

Section: Introductionmentioning

confidence: 99%

Reduced threading dislocation density in a germanium epitaxial film coalesced on an arrayed silicon-on-insulator strip

Amin

Motomura

Hizawa

et al. 2022

Jpn. J. Appl. Phys.

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This paper reports a reduction in the threading dislocation density (TDD) of a Ge epitaxial film on a Si-on-insulator (SOI) wafer in terms of the Si-photonics device application. An array of submicron SOI strips is prepared as a patterned substrate, on which Ge is epitaxially grown by chemical vapor deposition. A continuous Ge film is formed by a coalescence of the adjacent Ge crystals on the arrayed SOI strip, while leaving semicylindrical voids on the exposed surface of the buried SiO2 layer between the strips. The TDD of the coalesced Ge film is reduced to 1.0±0.1×108 cm–2, which is approximately a half of 2.2±0.2×108 cm–2 for a Ge film on an unpatterned SOI. A transmission electron microscope observation reveals that the TDD reduction is derived from a downward bending of the dislocation toward the void. An accumulation of the dislocations at the strip sidewalls also contributes to the TDD reduction.

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Defects and their reduction in Ge selective epitaxy and coalescence layer on Si with semicylindrical voids on SiO<formula> <tex>$_{2}$</tex> </formula> masks

Cited by 7 publications

References 30 publications

Dual-Step Selective Homoepitaxy of Ge with Low Defect Density and Modulated Strain Based on Optimized Ge/Si Virtual Substrate

Dual-Step Selective Homoepitaxy of Ge with Low Defect Density and Modulated Strain Based on Optimized Ge/Si Virtual Substrate

Strain Modulation of Selectively and/or Globally Grown Ge Layers

Reduced threading dislocation density in a germanium epitaxial film coalesced on an arrayed silicon-on-insulator strip

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