Size-tunable strain engineering in Ge nanocrystals embedded within SiO2 and Si3N4

Liao, Pei-Ju; Hsu, T.-C.; Chen, K. H.; Cheng, T. H.; Hsu, T. M.; Wang, C. C.; George, T.; Li, Peiwen

doi:10.1063/1.4900942

Cited by 21 publications

(26 citation statements)

References 33 publications

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“…In summary, the thicker Si1−xGex shells resulting from the larger Ge dots have shown us that Ge diffusion lengths in Si calculated using conventional formulas may have to be revised in light of the observed Ge-catalyzed Si vacancy enhancement. In addition to excellent crystallinity confirmed by the clear lattice fringes observed in the high-resolution TEM micrographs and SADs, our previous work (Liao et al, 2014) on the Raman characterization of the SiGe-shell region has shown a large blue shift of the longitudinal optical Ge-Ge phonon line (309 cm −1 from the SiGe shell as opposed to the 301 cm −1 for bulk Ge). This blue shift suggests the SiGe shell is being subjected to a compressive strain of ~1.6% and is therefore in reasonable agreement with the SAD analysis from Figure 4C.…”

Section: Discussionmentioning

confidence: 95%

“…Also, the appearance of a weak Raman signal at 406-414 cm −1 suggests that the chemical composition of the Si1−xGex shell has a strong dependence on the dot size. The Ge mole fraction is as high as x = 0.55-0.72 for the SiGe shells formed from 50 to 90 nm Ge dots (Pezzoli et al, 2008;Liao et al, 2014).…”

Section: Discussionmentioning

confidence: 96%

“…Detailed analysis of the SADs give the average lattice spacings of the {110}, {111}, and {311} SiGe planes as 3.928, 3.216, and 1.657 Å, corresponding to residual compressive strains of −1.60, −1, and −2.64%, respectively. Our previous work (Pezzoli et al, 2008;Liao et al, 2014) on the Raman characterization of the SiGe-shell region has also shown that Ge mole fractions as high as x = 0.55-0.72 are achieved for the SiGe shells formed from 50 to 90 nm Ge dots. The advantage of having single-crystalline Si1−xGex shells (x > 0.5) in a compressive stress state has extensive applications in nanoelectronics and nanophotonics, especially in SiGe (or Ge) p-MOS devices.…”

Section: It Is Observed Inmentioning

confidence: 99%

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Gate-Stack Engineering for Self-Organized Ge-dot/SiO2/SiGe-Shell MOS Capacitors

et al. 2016

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We report the first-of-its-kind, self-organized gate-stack heterostructure of Ge-dot/ SiO2/SiGe-shell on Si fabricated in a single step through the selective oxidation of a SiGe-nanopatterned pillar over a Si3N4 buffer layer on a Si substrate. Process-controlled tunability of the Ge-dot size (7.5-90 nm), the SiO2 thickness (3-4 nm), and the SiGeshell thickness (2-15 nm) have been demonstrated, enabling a practically achievable core building block for Ge-based metal-oxide-semiconductor (MOS) devices. Detailed morphologies, structural, and electrical interfacial properties of the SiO2/Ge-dot and SiO2/SiGe interfaces were assessed using transmission electron microscopy, energy dispersive X-ray spectroscopy, and temperature-dependent high/low-frequency capacitance-voltage measurements. Notably, NiGe/SiO2/SiGe and Al/SiO2/Ge-dot/SiO2/SiGe MOS capacitors exhibit low interface trap densities of as low as 3-5 × 10 11 cm −2 eV −1 and fixed charge densities of 1-5 × 10 11 cm −2, suggesting good-quality SiO2/SiGe-shell and SiO2/Ge-dot interfaces. In addition, the advantage of having single-crystalline Si1−xGex shell (x > 0.5) in a compressive stress state in our self-aligned gate-stack heterostructure has great promise for possible SiGe (or Ge) MOS nanoelectronic and nanophotonic applications.

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Section: Discussionmentioning

confidence: 95%

Section: Discussionmentioning

confidence: 96%

Section: It Is Observed Inmentioning

confidence: 99%

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Gate-Stack Engineering for Self-Organized Ge-dot/SiO2/SiGe-Shell MOS Capacitors

et al. 2016

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“…Below the interfacial oxide layer, an approximately 20-nm-thick Si 1- x Ge x shell is generated within the Si substrate. A substantial amount ( x ≈ 0.72) of Ge as estimated from the Raman signal at 414 cm −1 for the SiGe shells formed from the 90-nm Ge QDs [21, 22]. Clear lattice fringes are observed in the high-resolution CTEM micrographs (Fig.…”

Section: Resultsmentioning

confidence: 99%

A Unique Approach to Generate Self-Aligned SiO2/Ge/SiO2/SiGe Gate-Stacking Heterostructures in a Single Fabrication Step

et al. 2015

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We report a first-of-its-kind, unique approach for generating a self-aligned, gate-stacking heterostructure of Ge quantum dot (QD)/SiO2/SiGe shell on Si in a single fabrication step. The 4-nm-thick SiO2 layer between the Ge QD and SiGe shell fabricated during the single-step process is the result of an exquisitely controlled dynamic balance between the fluxes of oxygen and silicon interstitials. The high-quality interface properties of our “designer” heterostructure are evidenced by the low interface trap density of as low as 2–4 × 1011 cm−2 eV−1 and superior transfer characteristics measured for Ge-based metal-oxide-semiconductor field-effect transistors (MOSFETs). Thanks to the very thin interfacial SiO2 layer, carrier storage within the Ge QDs with good memory endurance was established under relatively low-voltage programming/erasing conditions. We hope that our unique self-aligned, gate-stacking heterostructure provides an effective approach for the production of next-generation, high-performance Ge gate/SiO2/SiGe channel MOSFETs.

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“…Remarkably, reducing the Ge dot size from 90 nm to 50 nm leads to an improvement in both normalized ON and OFF per unit Ge volume by a factor of 2.75 for Ge-dot PTs under both low- and high-power 850 nm illumination conditions. The improved IQE for the smaller Ge dots is possibly due to a significant improvement in crystallinity quality with reduced defect densities and an increased strain20, leading to better photoelectric conversion efficiency. As the nanodots get bigger, the statistical probability of having crystalline defects such as dislocations increases.…”

Section: Discussionmentioning

confidence: 99%

High Photoresponsivity Ge-dot PhotoMOSFETs for Low-power Monolithically-Integrated Si Optical Interconnects

Kuo

Lee

Lin

et al. 2017

Sci Rep

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We report the demonstration of high-photoresponsivity Ge-dot photoMOSFETs in a standard MOS configuration for the detection of 850–1550 nm illumination. Each device has a self-organized, gate-stacking heterostructure of SiO2/Ge-dot/SiO2/SiGe-channel which is simultaneously fabricated in a single oxidation step. Superior control of the geometrical size and chemical composition for our Ge nanodots/SiO2/Si1-xGex-shell MOS structure enables the practically-achievable, gate-stacking design for our Ge-dot photoMOSFETs. Both the gate oxide thickness and the diameter of the Ge dots are controllable. Large photocurrent enhancement was achieved for our Ge-dot photoMOSFETs when electrically-biased at ON- and OFF-states based on the Ge dot mediating photovoltaic and photoconductive effects, respectively. Both photoelectric conversion efficiency and response speed are significantly improved by reducing the gate-oxide thickness from 38.5 nm to 3.5 nm, and by decreasing Ge-dot size from 90 nm to 50 nm for a given areal density of Ge dots. Photoresponsivity () values as high as 1.2 × 104 A/W and 300 A/W are measured for 10 nW illumination at 850 nm and 1550 nm, respectively. A response time of 0.48 ns and a 3 dB-frequency of 2 GHz were achieved for 50 nm-Ge-dot photoMOSFETs with channel lengths of 3 μm under pulsed 850 nm illumination.

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Size-tunable strain engineering in Ge nanocrystals embedded within SiO2 and Si3N4

Cited by 21 publications

References 33 publications

Gate-Stack Engineering for Self-Organized Ge-dot/SiO2/SiGe-Shell MOS Capacitors

Gate-Stack Engineering for Self-Organized Ge-dot/SiO2/SiGe-Shell MOS Capacitors

A Unique Approach to Generate Self-Aligned SiO2/Ge/SiO2/SiGe Gate-Stacking Heterostructures in a Single Fabrication Step

High Photoresponsivity Ge-dot PhotoMOSFETs for Low-power Monolithically-Integrated Si Optical Interconnects

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