Saurabh Chopra | University of Lucknow (original) (raw)

Papers by Saurabh Chopra

BMJ Case Reports

Hyperekplexia is an exaggerated startle to external stimuli associated with a generalised increas... more Hyperekplexia is an exaggerated startle to external stimuli associated with a generalised increase in tone seen in neonates with both sporadic and genetic predisposition. This is an uncommon neurological entity that is misdiagnosed as seizure. A 28-days-old infant was admitted to us with characteristic intermittent generalised tonic spasm being treated as a seizure disorder. The infant had characteristic stiffening episode, exaggerated startle and non-habituation on tapping the nose. Hyperekplexia was suspected and confirmed by genetic testing (mutation in the β subunit of glycine was found). Initial improvement was seen with the use of clonazepam, which was not sustained. At the age of 4.5 years, the child is still having neurobehavioural issues like hyperactivity and sensory hyper-responsiveness. Usually, hyperekplexia is benign in nature. We report a case of hyperekplexia with non-sense mutation in the β subunit of GlyR gene having abnormal neurodevelopmental findings at 4.5 years.

ECS Transactions, 2020

Since ultra-highly doped, highly tensile strained Si:P epitaxy was reported about 10 years ago, i... more Since ultra-highly doped, highly tensile strained Si:P epitaxy was reported about 10 years ago, it quickly replaced Si:CP and become key processes for advanced nodes. With greater than 3E21 doping level, these films exhibit significant tensile stress and low resistivity, both enhanced the nMOS performance. As the technology scales, contact resistance is becoming a major factor for device performance, even higher activation level is desired. In this paper, the mechanisms for high doping level and tensile strain are briefly reviewed and discussed. Despite epitaxially grown, these films showed similar thermal equilibrium behavior as implant-annealed samples and could be predicted with well established model. Diffusion and strain analysis shed some lights on the processes involved in the carrier activation and deactivation. Formation of group V - vacancy complex, V4V, or Si3P4-like, structure is key to understand the behavior, especially dopant diffusion and interaction with vacancy. Un...

ECS Meeting Abstracts, 2012

not Available.

2013 5th IEEE International Memory Workshop, 2013

ABSTRACT Bipolar RRAM memory cells show different extents of asymmetry in set/reset voltages. Rec... more ABSTRACT Bipolar RRAM memory cells show different extents of asymmetry in set/reset voltages. Recently, our group has demonstrated a symmetric Si epitaxy based 4F2 punch-through diode based NPN selector. Here, we demonstrate that a modification of the doping profile of the NPN diode selector produces designable asymmetry in the I-V characteristics. We demonstrate based on a TCAD study that replacing the uniform p region in the symmetric NPN structure by an asymmetric p/p-bi-layer could lead to an asymmetry in the turn-on voltage |Von+|/|Von-| by a factor of ~1:2. Our calculations show that the on-current (few μA at 20nm technology node or >1MA/cm2) and on-voltage asymmetry control is adequate for various promising bipolar RRAM memory elements from literature. Finally, the on-voltage asymmetry control is experimentally demonstrated based on a low temperature (<;700°C) Si epitaxy process; the measured asymmetry in the new experimental devices is about |Von+|/|Von-|=1:2.1 compared to the a|Von+|/|Von-|=1:1.2 in the symmetric devices.

ABSTRACT Segmented-channel Si and SiGe P-MOSFETs (SegFETs) are compared against control devices f... more ABSTRACT Segmented-channel Si and SiGe P-MOSFETs (SegFETs) are compared against control devices fabricated using the same process but starting with non-corrugated substrates, with respect to key analog/RF performance metrics. SegFETs are found to have significant benefits due to their enhanced electrostatic integrity, lower series resistance and greater mobility enhancement, and hence show promise for future System-on-Chip applications.

70th Device Research Conference, 2012

ABSTRACT Resistive RAM is a very promising candidate for high density non-volatile memory. Althou... more ABSTRACT Resistive RAM is a very promising candidate for high density non-volatile memory. Although bipolar operation has been shown to work at lower current (essential for low power, mobile computing) [1], a suitable selector device that delivers high current density and high on/off current ratio is challenging [2–4]. We demonstrate a 4F2 bipolar selector device based on the punch-through mechanism. An npn vertical junction device fabricated using in-situ doped epitaxial silicon is presented. Superior on-current density (Jon=1MA/cm2) and high on-off current ratio (Ion/Ioff) of 300–5000 is experimentally demonstrated. TCAD simulations based performance, variability and scalability are presented.

68th Device Research Conference, 2010

For the first time, ultra shallow junctions (xj 1×1020 cm-3) is achieved for all dopant atoms (P/... more For the first time, ultra shallow junctions (xj 1×1020 cm-3) is achieved for all dopant atoms (P/As/Sb/B) using Laser Thermal Processing. We also show ultrathin (0.6nm), high quality GeO2 interfacial layer for gate dielectric, which provides substrate orientation independent Dit and mobility enhancement for Ge high-k N/P MOSFETs.

ECS Transactions, 2013

In-situ phosphorus doped silicon epitaxial film with 2.8 X 1021cm-3 doping level is found to show... more In-situ phosphorus doped silicon epitaxial film with 2.8 X 1021cm-3 doping level is found to show high tensile stress comparable to carbon doped silicon with 1.8% substitutional carbon. As-grown samples show electrically activated dopant concentration of less than 2 X 1020 cm-3. The high tensile and low activation could be well explained by formation of a pseudocubic Si3P4 structure in silicon lattice. Film resistivity of 0.29 mOhm-cm could be obtained with 0.25 ms annealing at 1200 {degree sign}C, with slight reduction in tensile strain. Also, 0.23 mOhm-cm could be obtained by millisecond anneal at 1300 {degree sign}C, but with 30% reduction in tensile strain.

ECS Transactions, 2008

Epitaxially grown Silicon Carbon (Si:C) in recessed junction regions has been shown to induce ten... more Epitaxially grown Silicon Carbon (Si:C) in recessed junction regions has been shown to induce tensile stress in the nMOS channel and thereby enhance the transistor performance. In addition to the stress induced in the channel, this technology also needs to achieve low resistivity junctions for widespread use. This work discusses epitaxially grown heavily doped Si/ Si:C layers which can be used in nMOS junctions and can address both these requirements. Si:C epitaxial layers are shown to have phosphorus concentrations as high as 1.25 X 10^21 cm^-3 with resistivities as low as 0.3 mOhm.cm. Applications of these layers can range from Si:P cap layers for low series resistance to Si:PC layers for inducing stress in the nMOS channel.

ECS Transactions, 2010

A continuous scaling of transistor devices is carried out by not only increasing the drive curren... more A continuous scaling of transistor devices is carried out by not only increasing the drive current but also reducing the off-state leakage current. For short channel devices, the reduction of leakage current is increasingly difficult and hence the use of multi-gate devices is looking increasingly more promising. One of the main areas of concern for multi-gate devices is the higher junction resistance due to high aspect ratio structures in these devices. Hence the use of epitaxy in these junctions is inevitable. In this work, we study the impact of process parameters on the final epitaxial junction shapes and how this affects the junction resistance. It is shown that the epitaxial junctions for n- and p-MOS have different shapes and hence will have to be controlled differently for the most optimum integration scheme.

Solid-State Electronics, 2013

Abstract Si n–i–p tunnel field-effect transistor (TFET) fabricated by plasma implantation and las... more Abstract Si n–i–p tunnel field-effect transistor (TFET) fabricated by plasma implantation and laser annealing is proposed. This TFET has sharp lateral source doping profile, which can reduce the tunneling distance and improve carrier tunneling. Enhanced on-current (12 μA/μm) and improved I ON / I OFF ratio (6 × 10 6 ) are observed in this TFET [ V DS = ( V GS − V BTBT ) = −1.1 V; V BTBT is the V GS at the lowest subthreshold current observed at given V DS ] at T = 300 K. In addition, the TFET fabricated by laser annealing shows improved subthreshold characteristics, reduced tunneling resistance and smaller threshold voltage than TFET fabricated by rapid thermal annealing. Low-temperature measurements of this TFET were also performed to confirm the carrier injection mechanism of band-to-band tunneling. Plasma implantation and laser annealing are effective and suitable to be applied in current CMOS technology for low power devices.

IEEE Electron Device Letters, 2011

ABSTRACT Highly activated n-type dopant is essential for n+/p germanium diodes which will be in u... more ABSTRACT Highly activated n-type dopant is essential for n+/p germanium diodes which will be in use for source/drain regions in Ge n-MOSFET as the geometry scaling proceeds. This letter has investigated a combination of ion implantation of Sb in Ge and subsequent laser annealing, which resulted in highly activated Sb beyond 1020 cm-3. Well-behaved Sb-doped nv/p Ge diode I-V characteristics have been demonstrated combined with TEM, SIMS, and spreading resistance profiling characterization.

Applied Physics Letters, 2006

The impact of heavy boron doping on the biaxial compressive strain in Si1−xGex layers grown on Si... more The impact of heavy boron doping on the biaxial compressive strain in Si1−xGex layers grown on Si has been investigated using Raman spectroscopy and theoretical calculations. It is shown that one boron atom is sufficient to compensate the strain due to approximately 6.9 Ge atoms. This effect is appreciably large for boron concentrations as low as 1%, typical for applications, which employ heavily boron doped layers. Using strain compensation, the Ge content can be substantially increased without increasing the stored strain energy. This phenomenon can be useful in applications, which require low-resistivity p-type strained Si1−xGex layers with high Ge content.

Proceedings of IEEE Sensors, 2004.

We present the design and development of a highly sensitive and fast response microwave resonant ... more We present the design and development of a highly sensitive and fast response microwave resonant sensor for monitoring the presence of gases present in the environment. The sensor consists of a circular disk electromagnetic resonant circuit coated with multi/single-walled carbon nanotubes that are highly sensitive to adsorbed gas molecules. Trace amounts (ppb) of gases or organic solvent vapors (polar or

infection (PANDAS) is a unique constellation of signs and symptoms that exist in a subset of chil... more infection (PANDAS) is a unique constellation of signs and symptoms that exist in a subset of children with rapid onset or exacerbation of obsessive-compulsive disorder (OCD) and/or tic disorders due to an initial autoimmune reaction to a Group A Beta Hemolytic Streptococcas (GABHS) infection which produce antibodies that interfere with the basal ganglia function. In PANDAS the usual onset is known to be before 12 years of age, however, it may also present (although rarely) in adolescence. With an aim to substantiate the existing database as well as create awareness about the same we report a case of PANDAS with adolescent onset.

2002 IEEE MTT-S International Microwave Symposium Digest (Cat. No.02CH37278)

... SC-29634 ' Dept. of Physics and Astronomy, Clemson University, Clemson, SC-29634 Abs... more ... SC-29634 ' Dept. of Physics and Astronomy, Clemson University, Clemson, SC-29634 Absfracf - We ... and sensors. The authors would like to thank Mr. Kris McGuire and Ms. B. Sadanadao for providing carbon nanotubes. This work ...

International Journal of Research in Pharmaceutical Sciences, 2019

Megaloblastic anemia and Myelodysplastic syndrome are generally considered mutually exclusive dia... more Megaloblastic anemia and Myelodysplastic syndrome are generally considered mutually exclusive diagnosis and at times becomes difficult to diagnose on the first encounter even after performing bone marrow examination. Aim of this study is to evaluate the role of LDH in the diagnosis of Megaloblastic anemia by treatment response at a tertiary care center in the northeastern part of India. Patients with age more than 12 years, Hemoglobin of patients less than 10 gm/dl, MCV ≥ 100 fl, Reticulocyte count <2.5 were included in the study. Based on serum LDH level patients were divided into two groups. Group A with serum LDH level ≥ 1200 U/L and Group B with serum LDH level of less than 1200 U/L. All these patients of serum LDH ≥1200 U/L were given a treatment trial of injectable Vitamin B12 containing 1000 μg of Vitamin B12 for 14 days. The response to treatment was monitored by an increment in reticulocyte count at day 5 and day 14. Bone marrow aspiration was done in all patients who ha...

BMJ Case Reports

Hyperekplexia is an exaggerated startle to external stimuli associated with a generalised increas... more Hyperekplexia is an exaggerated startle to external stimuli associated with a generalised increase in tone seen in neonates with both sporadic and genetic predisposition. This is an uncommon neurological entity that is misdiagnosed as seizure. A 28-days-old infant was admitted to us with characteristic intermittent generalised tonic spasm being treated as a seizure disorder. The infant had characteristic stiffening episode, exaggerated startle and non-habituation on tapping the nose. Hyperekplexia was suspected and confirmed by genetic testing (mutation in the β subunit of glycine was found). Initial improvement was seen with the use of clonazepam, which was not sustained. At the age of 4.5 years, the child is still having neurobehavioural issues like hyperactivity and sensory hyper-responsiveness. Usually, hyperekplexia is benign in nature. We report a case of hyperekplexia with non-sense mutation in the β subunit of GlyR gene having abnormal neurodevelopmental findings at 4.5 years.

ECS Transactions, 2020

Since ultra-highly doped, highly tensile strained Si:P epitaxy was reported about 10 years ago, i... more Since ultra-highly doped, highly tensile strained Si:P epitaxy was reported about 10 years ago, it quickly replaced Si:CP and become key processes for advanced nodes. With greater than 3E21 doping level, these films exhibit significant tensile stress and low resistivity, both enhanced the nMOS performance. As the technology scales, contact resistance is becoming a major factor for device performance, even higher activation level is desired. In this paper, the mechanisms for high doping level and tensile strain are briefly reviewed and discussed. Despite epitaxially grown, these films showed similar thermal equilibrium behavior as implant-annealed samples and could be predicted with well established model. Diffusion and strain analysis shed some lights on the processes involved in the carrier activation and deactivation. Formation of group V - vacancy complex, V4V, or Si3P4-like, structure is key to understand the behavior, especially dopant diffusion and interaction with vacancy. Un...

ECS Meeting Abstracts, 2012

not Available.

2013 5th IEEE International Memory Workshop, 2013

ABSTRACT Bipolar RRAM memory cells show different extents of asymmetry in set/reset voltages. Rec... more ABSTRACT Bipolar RRAM memory cells show different extents of asymmetry in set/reset voltages. Recently, our group has demonstrated a symmetric Si epitaxy based 4F2 punch-through diode based NPN selector. Here, we demonstrate that a modification of the doping profile of the NPN diode selector produces designable asymmetry in the I-V characteristics. We demonstrate based on a TCAD study that replacing the uniform p region in the symmetric NPN structure by an asymmetric p/p-bi-layer could lead to an asymmetry in the turn-on voltage |Von+|/|Von-| by a factor of ~1:2. Our calculations show that the on-current (few μA at 20nm technology node or &gt;1MA/cm2) and on-voltage asymmetry control is adequate for various promising bipolar RRAM memory elements from literature. Finally, the on-voltage asymmetry control is experimentally demonstrated based on a low temperature (&lt;;700°C) Si epitaxy process; the measured asymmetry in the new experimental devices is about |Von+|/|Von-|=1:2.1 compared to the a|Von+|/|Von-|=1:1.2 in the symmetric devices.

ABSTRACT Segmented-channel Si and SiGe P-MOSFETs (SegFETs) are compared against control devices f... more ABSTRACT Segmented-channel Si and SiGe P-MOSFETs (SegFETs) are compared against control devices fabricated using the same process but starting with non-corrugated substrates, with respect to key analog/RF performance metrics. SegFETs are found to have significant benefits due to their enhanced electrostatic integrity, lower series resistance and greater mobility enhancement, and hence show promise for future System-on-Chip applications.

70th Device Research Conference, 2012

ABSTRACT Resistive RAM is a very promising candidate for high density non-volatile memory. Althou... more ABSTRACT Resistive RAM is a very promising candidate for high density non-volatile memory. Although bipolar operation has been shown to work at lower current (essential for low power, mobile computing) [1], a suitable selector device that delivers high current density and high on/off current ratio is challenging [2–4]. We demonstrate a 4F2 bipolar selector device based on the punch-through mechanism. An npn vertical junction device fabricated using in-situ doped epitaxial silicon is presented. Superior on-current density (Jon=1MA/cm2) and high on-off current ratio (Ion/Ioff) of 300–5000 is experimentally demonstrated. TCAD simulations based performance, variability and scalability are presented.

68th Device Research Conference, 2010

For the first time, ultra shallow junctions (xj 1×1020 cm-3) is achieved for all dopant atoms (P/... more For the first time, ultra shallow junctions (xj 1×1020 cm-3) is achieved for all dopant atoms (P/As/Sb/B) using Laser Thermal Processing. We also show ultrathin (0.6nm), high quality GeO2 interfacial layer for gate dielectric, which provides substrate orientation independent Dit and mobility enhancement for Ge high-k N/P MOSFETs.

ECS Transactions, 2013

In-situ phosphorus doped silicon epitaxial film with 2.8 X 1021cm-3 doping level is found to show... more In-situ phosphorus doped silicon epitaxial film with 2.8 X 1021cm-3 doping level is found to show high tensile stress comparable to carbon doped silicon with 1.8% substitutional carbon. As-grown samples show electrically activated dopant concentration of less than 2 X 1020 cm-3. The high tensile and low activation could be well explained by formation of a pseudocubic Si3P4 structure in silicon lattice. Film resistivity of 0.29 mOhm-cm could be obtained with 0.25 ms annealing at 1200 {degree sign}C, with slight reduction in tensile strain. Also, 0.23 mOhm-cm could be obtained by millisecond anneal at 1300 {degree sign}C, but with 30% reduction in tensile strain.

ECS Transactions, 2008

Epitaxially grown Silicon Carbon (Si:C) in recessed junction regions has been shown to induce ten... more Epitaxially grown Silicon Carbon (Si:C) in recessed junction regions has been shown to induce tensile stress in the nMOS channel and thereby enhance the transistor performance. In addition to the stress induced in the channel, this technology also needs to achieve low resistivity junctions for widespread use. This work discusses epitaxially grown heavily doped Si/ Si:C layers which can be used in nMOS junctions and can address both these requirements. Si:C epitaxial layers are shown to have phosphorus concentrations as high as 1.25 X 10^21 cm^-3 with resistivities as low as 0.3 mOhm.cm. Applications of these layers can range from Si:P cap layers for low series resistance to Si:PC layers for inducing stress in the nMOS channel.

ECS Transactions, 2010

A continuous scaling of transistor devices is carried out by not only increasing the drive curren... more A continuous scaling of transistor devices is carried out by not only increasing the drive current but also reducing the off-state leakage current. For short channel devices, the reduction of leakage current is increasingly difficult and hence the use of multi-gate devices is looking increasingly more promising. One of the main areas of concern for multi-gate devices is the higher junction resistance due to high aspect ratio structures in these devices. Hence the use of epitaxy in these junctions is inevitable. In this work, we study the impact of process parameters on the final epitaxial junction shapes and how this affects the junction resistance. It is shown that the epitaxial junctions for n- and p-MOS have different shapes and hence will have to be controlled differently for the most optimum integration scheme.

Solid-State Electronics, 2013

Abstract Si n–i–p tunnel field-effect transistor (TFET) fabricated by plasma implantation and las... more Abstract Si n–i–p tunnel field-effect transistor (TFET) fabricated by plasma implantation and laser annealing is proposed. This TFET has sharp lateral source doping profile, which can reduce the tunneling distance and improve carrier tunneling. Enhanced on-current (12 μA/μm) and improved I ON / I OFF ratio (6 × 10 6 ) are observed in this TFET [ V DS = ( V GS − V BTBT ) = −1.1 V; V BTBT is the V GS at the lowest subthreshold current observed at given V DS ] at T = 300 K. In addition, the TFET fabricated by laser annealing shows improved subthreshold characteristics, reduced tunneling resistance and smaller threshold voltage than TFET fabricated by rapid thermal annealing. Low-temperature measurements of this TFET were also performed to confirm the carrier injection mechanism of band-to-band tunneling. Plasma implantation and laser annealing are effective and suitable to be applied in current CMOS technology for low power devices.

IEEE Electron Device Letters, 2011

ABSTRACT Highly activated n-type dopant is essential for n+/p germanium diodes which will be in u... more ABSTRACT Highly activated n-type dopant is essential for n+/p germanium diodes which will be in use for source/drain regions in Ge n-MOSFET as the geometry scaling proceeds. This letter has investigated a combination of ion implantation of Sb in Ge and subsequent laser annealing, which resulted in highly activated Sb beyond 1020 cm-3. Well-behaved Sb-doped nv/p Ge diode I-V characteristics have been demonstrated combined with TEM, SIMS, and spreading resistance profiling characterization.

Applied Physics Letters, 2006

The impact of heavy boron doping on the biaxial compressive strain in Si1−xGex layers grown on Si... more The impact of heavy boron doping on the biaxial compressive strain in Si1−xGex layers grown on Si has been investigated using Raman spectroscopy and theoretical calculations. It is shown that one boron atom is sufficient to compensate the strain due to approximately 6.9 Ge atoms. This effect is appreciably large for boron concentrations as low as 1%, typical for applications, which employ heavily boron doped layers. Using strain compensation, the Ge content can be substantially increased without increasing the stored strain energy. This phenomenon can be useful in applications, which require low-resistivity p-type strained Si1−xGex layers with high Ge content.

Proceedings of IEEE Sensors, 2004.

We present the design and development of a highly sensitive and fast response microwave resonant ... more We present the design and development of a highly sensitive and fast response microwave resonant sensor for monitoring the presence of gases present in the environment. The sensor consists of a circular disk electromagnetic resonant circuit coated with multi/single-walled carbon nanotubes that are highly sensitive to adsorbed gas molecules. Trace amounts (ppb) of gases or organic solvent vapors (polar or

infection (PANDAS) is a unique constellation of signs and symptoms that exist in a subset of chil... more infection (PANDAS) is a unique constellation of signs and symptoms that exist in a subset of children with rapid onset or exacerbation of obsessive-compulsive disorder (OCD) and/or tic disorders due to an initial autoimmune reaction to a Group A Beta Hemolytic Streptococcas (GABHS) infection which produce antibodies that interfere with the basal ganglia function. In PANDAS the usual onset is known to be before 12 years of age, however, it may also present (although rarely) in adolescence. With an aim to substantiate the existing database as well as create awareness about the same we report a case of PANDAS with adolescent onset.

2002 IEEE MTT-S International Microwave Symposium Digest (Cat. No.02CH37278)

... SC-29634 &#x27; Dept. of Physics and Astronomy, Clemson University, Clemson, SC-29634 Abs... more ... SC-29634 &#x27; Dept. of Physics and Astronomy, Clemson University, Clemson, SC-29634 Absfracf - We ... and sensors. The authors would like to thank Mr. Kris McGuire and Ms. B. Sadanadao for providing carbon nanotubes. This work ...

International Journal of Research in Pharmaceutical Sciences, 2019

Megaloblastic anemia and Myelodysplastic syndrome are generally considered mutually exclusive dia... more Megaloblastic anemia and Myelodysplastic syndrome are generally considered mutually exclusive diagnosis and at times becomes difficult to diagnose on the first encounter even after performing bone marrow examination. Aim of this study is to evaluate the role of LDH in the diagnosis of Megaloblastic anemia by treatment response at a tertiary care center in the northeastern part of India. Patients with age more than 12 years, Hemoglobin of patients less than 10 gm/dl, MCV ≥ 100 fl, Reticulocyte count <2.5 were included in the study. Based on serum LDH level patients were divided into two groups. Group A with serum LDH level ≥ 1200 U/L and Group B with serum LDH level of less than 1200 U/L. All these patients of serum LDH ≥1200 U/L were given a treatment trial of injectable Vitamin B12 containing 1000 μg of Vitamin B12 for 14 days. The response to treatment was monitored by an increment in reticulocyte count at day 5 and day 14. Bone marrow aspiration was done in all patients who ha...