Defect formation during growth of hydrogenated amorphous silicon

Ganguly, Gautam; Matsuda, Akihisa

doi:10.1103/physrevb.47.3661

Cited by 163 publications

(67 citation statements)

References 51 publications

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“…The importance of the substrate temperature in growth of device quality a-Si:H films may be balancing the increasing diffusion of SiH 3 , which improves film flatness, and the loss of hydrogen from the films, which introduces more dangling bonds, degrading film flatness. 50 Collins and Yang have shown that smoothing of well-characterized polycrystalline substrate roughness by subsequent a-Si:H deposition determines a diffusion length between 6 and 10 nm. 38 It is not clear if this value represents mobility of the SiH 3 precursor or the dangling bond.…”

Section: E Diffusion Lengthmentioning

confidence: 99%

Surface roughening during plasma-enhanced chemical-vapor deposition of hydrogenated amorphous silicon on crystal silicon substrates

1997

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The morphology of a series of thin films of hydrogenated amorphous silicon ͑a-Si:H͒ grown by plasmaenhanced chemical-vapor deposition ͑PECVD͒ is studied using scanning tunneling microscopy. The substrates were atomically flat, oxide-free, single-crystal silicon. Films were grown in a PECVD chamber directly connected to a surface analysis chamber with no air exposure between growth and measurement. The homogeneous roughness of the films increases with film thickness. The quantification of this roughening is achieved by calculation of both rms roughness and lateral correlation lengths of the a-Si:H film surface from the height difference correlation functions of the measured topographs. Homogeneous roughening occurs over the film surface due to the collective behavior of the flux of depositing radical species and their interactions with the growth surface. ͓S0163-1829͑97͒04932-1͔

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Section: E Diffusion Lengthmentioning

confidence: 99%

Surface roughening during plasma-enhanced chemical-vapor deposition of hydrogenated amorphous silicon on crystal silicon substrates

1997

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“…28 If we assume as in Mason 7 and Richardson et al 17 that H coverage prevents contaminants, such as C and O, from depositing onto the surface, but does allow Si to deposit, then at higher substrate temperatures increased hydrogen desorption leads to higher contaminant incorporation, which would increase the surface roughness with increasing substrate temperature. 13,17,29 Moreover, given that the H coverage of the Si͑100͒ surface at high H dilutions is large and temperature independent below 300°C, 30 then as we lower the substrate temperature from 270°C to 230°C, we suggest that film growth becomes surface mobility limited and there is an increase in the film roughness once more.…”

Section: A Thin Film Structure and Crystallinitymentioning

confidence: 99%

Surface evolution during crystalline silicon film growth by low-temperature hot-wire chemical vapor deposition on silicon substrates

2006

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We investigate the low-temperature growth of crystalline thin silicon films: epitaxial, twinned, and polycrystalline, by hot-wire chemical vapor deposition ͑HWCVD͒. Using Raman spectroscopy, spectroscopic ellipsometry, and atomic force microscopy, we find the relationship between surface roughness evolution and ͑i͒ the substrate temperature ͑230-350°C͒ and ͑ii͒ the hydrogen dilution ratio ͑H 2 / SiH 4 =0-480͒. The absolute silicon film thickness for fully crystalline films is found to be the most important parameter in determining surface roughness, hydrogen being the second most important. Higher hydrogen dilution increases the surface roughness as expected. However, surface roughness increases with increasing substrate-temperature, in contrast to previous studies of crystalline Si growth. We suggest that the temperature-dependent roughness evolution is due to the role of hydrogen during the HWCVD process, which in this high hydrogen dilution regime allows for epitaxial growth on the rms roughest films through a kinetic growth regime of shadow-dominated etch and desorption and redeposition of growth species.

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“…Amorphous Si deposited by PECVD is subjected to significant H incorporation into the Si during deposition, with hydrogen concentrations of approximately 10 at. % depending on the deposition conditions [44,45]. At concentrations greater than 10 at.…”

Section: Designmentioning

confidence: 99%

“…However, the Ge growth rates at low temperature are slow, with growth rates observed at between 75 nm h-1 to 100 nm h-1, depending on growth pressure. Therefore, it is impractical to grow a single crystallite to tens of microns in order to fill the trench because growth times would be several 45 Chapter 2. Germanium Growth on Amorphous Substrates days to weeks long.…”

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confidence: 99%

Germanium photodetectors on amorphous substrates for electronic-photonic integration

Pearson

Kimerling

Michel³

2016

2016 IEEE 13th International Conference on Group IV Photonics (GFP)

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Silicon photonics has emerged as a leading technology to overcome the bandwidth and energy efficiency bottlenecks of standard metal interconnects. Integration of photonics in the back-end-of-line (BEOL) of a standard CMOS process enables the advantages of optical interconnects while benefiting from the low cost of monolithic integration. However, processing in the BEOL requires device fabrication on amorphous substrates, and constrains processing to <450C. In this thesis, a germanium photodetector is fabricated while adhering to these processing constraints in order to demonstrate a proof of concept for BEOL integration.In order to obtain high quality active material, crystalline Ge was grown on Si0 2 by implementing selective deposition in geometrically confined channels. The emerging Ge grains were coalesced to fill a lithographically defined trench, forming the active area of a photodetector. The Ge was measured to have a significant tensile strain of 0.5 %, which was caused by thermal expansion mismatch with the substrate, and concentrated by small voids from imperfect coalescence. The associated resolved shear stress was determined to be below the critical resolved shear stress, verifying that dislocation generation does not occur in this material. The strain was shown to increase the absorption of Ge at long wavelengths, allowing for implementation along the entire telecom window.A Schottky barrier to p-type Ge was developed by the addition of a 1 nm tunneling A1 2 0 3 layer between an Al/Ge metal contact. This successfully de-pinned the Fermi level, creating a barrier height of 0.46 eV. The Schottky contacts enabled the fabrication of metal-semiconductor-metal (MSM) photodetectors on standard epitaxial Ge with state-of-the-art dark current densities of 2.1 x 10-2 A cm-2. Gain was observed in these photodetectors, with internal quantum efficiencies (IQE) of 405 %. MSM detectors were also made using Ge on Si0 2 , exhibiting an IQE of 370 %. This is the first demonstration of IQE >100% in a Ge MSM or pin photodetector and proves the feasibility of making high performance active photonic devices while adhering to BEOL processing constraints. AcknowledgmentsFinishing this thesis was more challenging than I expected it would be when I started at MIT nearly six years ago. I doubt I would have been able to complete my PhD if it were not for a tremendous amount of help along the way.My two advisors, Kim and Jurgen have both helped guide me through this entire process. There were some challenges associated with having two advisors. At times I was pulled in different directions as Kim was always more interested in materials development and analysis, while Jurgen was always more interested in final device performance. Ultimately, it was in my benefit to constantly have both perspectives pushing me to have a well-rounded project. It seems as if there is nothing that Kim does not know, and Jurgen has always been available when I knock on his door at a random time seeking his help. They were both crucial to my ...

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Defect formation during growth of hydrogenated amorphous silicon

Cited by 163 publications

References 51 publications

Surface roughening during plasma-enhanced chemical-vapor deposition of hydrogenated amorphous silicon on crystal silicon substrates

Surface roughening during plasma-enhanced chemical-vapor deposition of hydrogenated amorphous silicon on crystal silicon substrates

Surface evolution during crystalline silicon film growth by low-temperature hot-wire chemical vapor deposition on silicon substrates

Germanium photodetectors on amorphous substrates for electronic-photonic integration

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