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- Physics, Engineering, Materials Science and Engineering, Materials Characterisation, Nanoelectronics, Electronics, and 12 moreNanotechnology, Materials Science, Materials Engineering, Materials, Semiconductor Physics, Microelectronics And Semiconductor Engineering, Materials Chemistry, Semiconductors, Semiconductor Devices, Semiconductor Nanostructures, Electronic Materials, and Siliconedit
- Fundamental study of Material processing, Electrical characterization and the defect analysis of Epitaxial filmsedit
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We perform a systematic study on the growth of epitaxial Silicon–Oxygen superlattices (SLs) and investigate the impact ofstructural properties on the electrical performance. Si layers and O atomic layers (ALs) are deposited using SiH4 and... more
We perform a systematic study on the growth of epitaxial Silicon–Oxygen superlattices (SLs) and investigate the impact ofstructural properties on the electrical performance. Si layers and O atomic layers (ALs) are deposited using SiH4 and O3 reactions respectively. Although the deposition of O ALs and epitaxial Si thereon, i.e. 1st period of Si–O SL is well documented, the controlled deposition in maintaining the overall crystalline quality of SL is stilla challenge. This is due to inability to limit the O layer to sub-AL content (1AL = 6.7 × 1014 at/cm2) at higher periods (≥2). The Si surface prior to O AL deposition is chemically modified with H-passivation and sub-AL O-contentis achieved. This ensures minimum structural distortions, enabling epitaxial ordering of Si and hence the epitaxial Si–O SLup to 5-periods. No SiOx clusters are detected and O layers are stable at Si deposition temperature. Electrically, donor defects increase with Si–Operiods and partially reduced with forming gas anneal. The presence of defects and increased roughness during the growth,degrade the mobility due to coulomb and surface scattering respectively. It can be circumvented by optimizing SL parametersand other process integration parameters subjected for future research.status: publishe
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Abstract The epitaxial growth of Si layers on Si substrates in the presence of O atoms is generally considered a challenge, as O atoms degrade the epitaxial quality by generating defects. Here, we investigate the growth mechanisms for Si... more
Abstract The epitaxial growth of Si layers on Si substrates in the presence of O atoms is generally considered a challenge, as O atoms degrade the epitaxial quality by generating defects. Here, we investigate the growth mechanisms for Si epitaxy on O atomic layers (ALs) with different O-contents and structures. O ALs are deposited by ozone (O3) or oxygen (O2) exposure on H-terminated Si at 50 °C and 300 °C respectively. Epitaxial Si is deposited by chemical vapor deposition using silane (SiH4) at 500 °C. After O3 exposure, the O atoms are uniformly distributed in Si-Si dimer/back bonds. This O layer still allows epitaxial seeding of Si. The epitaxial quality is enhanced by lowering the surface distortions due to O atoms and by decreasing the arrival rate of SiH4 reactants, allowing more time for surface diffusion. After O2 exposure, the O atoms are present in the form of SiOx clusters. Regions of hydrogen-terminated Si remain present between the SiOx clusters. The epitaxial seeding of Si in these structures is realized on H-Si regions, and an epitaxial layer grows by a lateral overgrowth mechanism. A breakdown in the epitaxial ordering occurs at a critical Si thickness, presumably by accumulation of surface roughness.
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Photonic Integrated Circuits (PICs) in the visible wavelength range have been extensively used for life science applications. Silicon Nitride has been the most widely used material, as it allows to fabricate low loss waveguides with the... more
Photonic Integrated Circuits (PICs) in the visible wavelength range have been extensively used for life science applications. Silicon Nitride has been the most widely used material, as it allows to fabricate low loss waveguides with the refractive index ranging from 1.9 to 2.1. For downscaling of PICs, many investigations into Titanium Oxide (TiO2) have been studied. The refractive index of TiO2 ranges from 2.3 to 2.6. Despite a high refractive index, TiO2 tends to crystallize at temperatures above 300oC, limiting its potential for CMOS compatible fabrication. In addition, the presence of oxygen vacancies in TiO2 results into photon absorption in the visible range, leading to high propagation losses. We investigate Niobium Oxide (Nb2O5) as an alternative waveguide material, focusing on material and optical properties for light propagation in the visible wavelength range. Physical vapor deposition of the Nb target in Oxygen atmosphere results in stoichiometric Nb2O5. On a 200mm wafer, a 90nm Nb2O5 is deposited on 2.3µm bottom clad (SiO2). The extracted refractive index is above 2.3, while the extinction coefficient is 0 for visible wavelengths. From X-ray diffraction, the as-deposited layers were amorphous, while the surface roughness was below 0.3 nm. Waveguides were patterned using 193 nm lithography and etched using chlorine based chemistry. In the visible range, optical losses for un-cladded waveguides were below 5 dB/cm, comparable to our in-house SiN platform. There were no significant changes in optical losses after 400oC anneal, signifying its potential for improved propagation after top-cladding deposition.
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This work reports on the deep levels observed in Pt/Al2O3/p-type Si metal-oxide-semiconductor capacitors containing a silicon-oxygen superlattice (SL) by deep-level transient spectroscopy. It is shown that the presence of the SL gives... more
This work reports on the deep levels observed in Pt/Al2O3/p-type Si metal-oxide-semiconductor capacitors containing a silicon-oxygen superlattice (SL) by deep-level transient spectroscopy. It is shown that the presence of the SL gives rise to a broad band of hole traps occurring around the silicon mid gap, which is absent in reference samples with a silicon epitaxial layer. In addition, the density of states of the deep layers roughly scales with the number of SL periods for the as- deposited samples. Annealing in a forming gas atmosphere reduces the maximum concentration significantly, while the peak energy position shifts from close-to mid-gap towards the valence band edge. Based on the flat-band voltage shift of the Capacitance-Voltage characteristics it is inferred that positive charge is introduced by the oxygen atomic layers in the SL, indicating the donor nature of the underlying hole traps. In some cases, a minor peak associated with P-b dangling bond centers at the Si/SiO2 interface has been observed as well.
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We perform a systematic study on the growth of epitaxial Silicon–Oxygen superlattices (SLs) and investigate the impact ofstructural properties on the electrical performance. Si layers and O atomic layers (ALs) are deposited using SiH4 and... more
We perform a systematic study on the growth of epitaxial Silicon–Oxygen superlattices (SLs) and investigate the impact ofstructural properties on the electrical performance. Si layers and O atomic layers (ALs) are deposited using SiH4 and O3 reactions respectively. Although the deposition of O ALs and epitaxial Si thereon, i.e. 1st period of Si–O SL is well documented, the controlled deposition in maintaining the overall crystalline quality of SL is stilla challenge. This is due to inability to limit the O layer to sub-AL content (1AL = 6.7 × 1014 at/cm2) at higher periods (≥2). The Si surface prior to O AL deposition is chemically modified with H-passivation and sub-AL O-contentis achieved. This ensures minimum structural distortions, enabling epitaxial ordering of Si and hence the epitaxial Si–O SLup to 5-periods. No SiOx clusters are detected and O layers are stable at Si deposition temperature. Electrically, donor defects increase with Si–Operiods and partially reduced with forming gas anneal. The presence of defects and increased roughness during the growth,degrade the mobility due to coulomb and surface scattering respectively. It can be circumvented by optimizing SL parametersand other process integration parameters subjected for future research.status: publishe
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In this paper, the deep levels found by Deep-Level Transient Spectroscopy in Si-O superlattices (SLs) on n-type silicon are reported. Samples have been grown with one, two or five silicon-oxygen layers, separated by 3 nm of silicon. A Cr... more
In this paper, the deep levels found by Deep-Level Transient Spectroscopy in Si-O superlattices (SLs) on n-type silicon are reported. Samples have been grown with one, two or five silicon-oxygen layers, separated by 3 nm of silicon. A Cr Schottky barrier (SB) is thermally evaporated on top of the SL. Similar as for p-type silicon, no deep levels have been found for a bias pulse in depletion, while a broad distribution of electron traps shows up when pulsing into forward bias. At the same time, these bands are absent in a zero SL reference sample. Similar as for the p-type results, the trap filling of the electron states exhibits a logarithmic capture. The possible origin of this slow filling will be discussed.
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In this paper, the deep levels found by deep-level transient spectroscopy in Si-O superlattices on p-type silicon substrates are compared with the band of near mid-gap hole traps typically observed at the Si/SiO2 interface. In addition,... more
In this paper, the deep levels found by deep-level transient spectroscopy in Si-O superlattices on p-type silicon substrates are compared with the band of near mid-gap hole traps typically observed at the Si/SiO2 interface. In addition, the impact of a post-deposition Forming Gas Annealing is investigated. A large similarity between the two material systems is reported, which indicates that similar silicon-oxygen bonds may be responsible for the deep hole traps.(© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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Photonic Integrated Circuits (PICs) in the visible wavelength range have been extensively used for life science applications. Silicon Nitride has been the most widely used material, as it allows to fabricate low loss waveguides with the... more
Photonic Integrated Circuits (PICs) in the visible wavelength range have been extensively used for life science applications. Silicon Nitride has been the most widely used material, as it allows to fabricate low loss waveguides with the refractive index ranging from 1.9 to 2.1. For downscaling of PICs, many investigations into Titanium Oxide (TiO2) have been studied. The refractive index of TiO2 ranges from 2.3 to 2.6. Despite a high refractive index, TiO2 tends to crystallize at temperatures above 300oC, limiting its potential for CMOS compatible fabrication. In addition, the presence of oxygen vacancies in TiO2 results into photon absorption in the visible range, leading to high propagation losses. We investigate Niobium Oxide (Nb2O5) as an alternative waveguide material, focusing on material and optical properties for light propagation in the visible wavelength range. Physical vapor deposition of the Nb target in Oxygen atmosphere results in stoichiometric Nb2O5. On a 200mm wafer...
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We investigate niobium oxide (NbO) as an alternative waveguide material for applications in the visible spectral range. NbO has a refractive index ranging between 2.3 and 2.35, which is about 25% higher than SiN, the most widely used... more
We investigate niobium oxide (NbO) as an alternative waveguide material for applications in the visible spectral range. NbO has a refractive index ranging between 2.3 and 2.35, which is about 25% higher than SiN, the most widely used material for waveguides in the visible spectral range. This increased index contrast between NbO and the cladding material allows to fabricate optical components with much smaller footprint, and consequently to increase the density of photonic integrated circuits substantially. We benchmark this waveguide platform to imec’s CMOS compatible PECVD SiN platform and observe fairly similar loss numbers for both materials.
This work reports on the deep levels observed in Pt/Al2O3/p-type Si metal-oxide-semiconductor capacitors containing a silicon-oxygen superlattice (SL) by deep-level transient spectroscopy. It is shown that the presence of the SL gives... more
This work reports on the deep levels observed in Pt/Al2O3/p-type Si metal-oxide-semiconductor capacitors containing a silicon-oxygen superlattice (SL) by deep-level transient spectroscopy. It is shown that the presence of the SL gives rise to a broad band of hole traps occurring around the silicon mid gap, which is absent in reference samples with a silicon epitaxial layer. In addition, the density of states of the deep layers roughly scales with the number of SL periods for the as- deposited samples. Annealing in a forming gas atmosphere reduces the maximum concentration significantly, while the peak energy position shifts from close-to mid-gap towards the valence band edge. Based on the flat-band voltage shift of the Capacitance-Voltage characteristics it is inferred that positive charge is introduced by the oxygen atomic layers in the SL, indicating the donor nature of the underlying hole traps. In some cases, a minor peak associated with P-b dangling bond centers at the Si/SiO2 interface has been observed as well.
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ABSTRACT Applied Surface Science j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / a p s u s c Deposition of O atomic layers on Si(100) substrates for epitaxial Si-O superlattices: investigation of the... more
ABSTRACT Applied Surface Science j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / a p s u s c Deposition of O atomic layers on Si(100) substrates for epitaxial Si-O superlattices: investigation of the surface chemistry a b s t r a c t Epitaxial Si-O superlattices consist of alternating periods of crystalline Si layers and atomic layers of oxygen (O) with interesting electronic and optical properties. To understand the fundamentals of Si epitaxy on O atomic layers, we investigate the O surface species that can allow epitaxial Si chemical vapor deposition using silane. The surface reaction of ozone on H-terminated Si(100) is used for the O deposition. The oxygen content is controlled precisely at and near the atomic layer level and has a critical impact on the subsequent Si deposition. There exists only a small window of O-contents, i.e. 0.7–0.9 atomic layers, for which the epitaxial deposition of Si can be realized. At these low O-contents, the O atoms are incorporated in the Si-Si dimers or back bonds (-OSiH), with the surface Si atoms mainly in the 1+ oxidation state, as indicated by infrared spectroscopy. This surface enables epitaxial seeding of Si. For O-contents higher than one atomic layer, the additional O atoms are incorporated in the Si-Si back bonds as well as in the Si-H bonds, where hydroxyl groups (-Si-OH) are created. In this case, the Si deposition thereon becomes completely amorphous.
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ABSTRACT Applied Surface Science j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / a p s u s c Deposition of O atomic layers on Si(100) substrates for epitaxial Si-O superlattices: investigation of the... more
ABSTRACT Applied Surface Science j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / a p s u s c Deposition of O atomic layers on Si(100) substrates for epitaxial Si-O superlattices: investigation of the surface chemistry a b s t r a c t Epitaxial Si-O superlattices consist of alternating periods of crystalline Si layers and atomic layers of oxygen (O) with interesting electronic and optical properties. To understand the fundamentals of Si epitaxy on O atomic layers, we investigate the O surface species that can allow epitaxial Si chemical vapor deposition using silane. The surface reaction of ozone on H-terminated Si(100) is used for the O deposition. The oxygen content is controlled precisely at and near the atomic layer level and has a critical impact on the subsequent Si deposition. There exists only a small window of O-contents, i.e. 0.7–0.9 atomic layers, for which the epitaxial deposition of Si can be realized. At these low O-contents, the O atoms are incorporated in the Si-Si dimers or back bonds (-OSiH), with the surface Si atoms mainly in the 1+ oxidation state, as indicated by infrared spectroscopy. This surface enables epitaxial seeding of Si. For O-contents higher than one atomic layer, the additional O atoms are incorporated in the Si-Si back bonds as well as in the Si-H bonds, where hydroxyl groups (-Si-OH) are created. In this case, the Si deposition thereon becomes completely amorphous.
Research Interests:
We perform a systematic study on the growth of epitaxial Silicon–Oxygen superlattices (SLs) and investigate the impact of structural properties on the electrical performance. Si layers and O atomic layers (ALs) are deposited using SiH 4... more
We perform a systematic study on the growth of epitaxial Silicon–Oxygen superlattices (SLs) and investigate the impact of structural properties on the electrical performance. Si layers and O atomic layers (ALs) are deposited using SiH 4 and O 3 reactions respectively. Although the deposition of O ALs and epitaxial Si thereon, i.e. 1 st period of Si–O SL is well documented, the controlled deposition in maintaining the overall crystalline quality of SL is still a challenge. This is due to inability to limit the O layer to sub-AL content (1AL = 6.7 × 10 14 at/cm 2) at higher periods (≥2). The Si surface prior to O AL deposition is chemically modified with H-passivation and sub-AL O-content is achieved. This ensures minimum structural distortions, enabling epitaxial ordering of Si and hence the epitaxial Si–O SL up to 5-periods. No SiO x clusters are detected and O layers are stable at Si deposition temperature. Electrically, donor defects increase with Si–O periods and partially reduced with forming gas anneal. The presence of defects and increased roughness during the growth, degrade the mobility due to coulomb and surface scattering respectively. It can be circumvented by optimizing SL parameters and other process integration parameters subjected for future research.
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Abstract: We have investigated a novel approach of introducing a combined capping of quaternary alloy (InAlGaAs) and GaAs layer for the realization of stacked quantum dots (QD) heterostructure, in which the InAlGaAs act as a... more
Abstract: We have investigated a novel approach of introducing a combined capping of quaternary alloy (InAlGaAs) and GaAs layer for the realization of stacked quantum dots (QD) heterostructure, in which the InAlGaAs act as a surface-strain-driven phase separation alloy activated by the predeposited InAs QDs. For a heterostructure sample with thin barrier thickness, high resolution transmission electron microscopy (HRTEM) image showed the stacking of QDs only upto the 5th layer and in the upper layers the dots are missing. We ...
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This work reports on the deep levels observed in Pt/Al 2 O 3 /p-type Si metal-oxide-semiconductor capacitors containing a silicon–oxygen superlattice (SL) by deep-level transient spectroscopy. It is shown that the presence of the SL gives... more
This work reports on the deep levels observed in Pt/Al 2 O 3 /p-type Si metal-oxide-semiconductor capacitors containing a silicon–oxygen superlattice (SL) by deep-level transient spectroscopy. It is shown that the presence of the SL gives rise to a broad band of hole traps occurring around the silicon mid gap, which is absent in reference samples with a silicon epitaxial layer. In addition, the density of states of the deep layers roughly scales with the number of SL periods for the as-deposited samples. Annealing in a forming gas atmosphere reduces the maximum concentration significantly, while the peak energy position shifts from close-to mid-gap towards the valence band edge. Based on the flat-band voltage shift of the Capacitance–Voltage characteristics it is inferred that positive charge is introduced by the oxygen atomic layers in the SL, indicating the donor nature of the underlying hole traps. In some cases, a minor peak associated with P b dangling bond centers at the Si/SiO 2 interface has been observed as well.