Binita Tongbram - Academia.edu (original) (raw)

Papers by Binita Tongbram

Materials Science in Semiconductor Processing, 2020

It is already established that Poole-Frenkel (PF) transport is the dominant method of current tra... more It is already established that Poole-Frenkel (PF) transport is the dominant method of current transport in goldcatalyzed, Vapor-Liquid-Solid (VLS) grown, intrinsic silicon nanowires. However, this is contrary to common knowledge in the field. PF transport is often used to model the current-voltage (IV) relationship of materials without long-range order. In this study, the physical nature of the coulomb traps responsible for PF transport in VLS grown silicon nanowires has been investigated. It has been found that, VLS grown, single crystal silicon nanowires have small regions (<25 nm 2) of crystallographic misorientation throughout their volume. This, along with the twin boundaries found in the analysis, can periodically trap and detrap charge carriers traversing between the metal contacts on silicon nanowires. It is proposed that the omnipresence of these defects in the channel region to be the origin of PF transport in VLS grown silicon nanowires.

Materials Research Bulletin, 2017

Abstract GaAs 1−x N x /GaAs multiple quantum wells (MQWs) were grown on GaAs(001) substrates thro... more Abstract GaAs 1−x N x /GaAs multiple quantum wells (MQWs) were grown on GaAs(001) substrates through solid-source molecular beam epitaxy under various nitrogen background pressures (NBPs), and the crystal quality at the interface of GaAs 1−x N x and GaAs was investigated. X-ray diffraction and electron microscopy confirmed the low interface roughness of MQWs grown at a NBP of 5 × 10 −6 Torr. Surface morphology measurements revealed a smooth surface without whisker-like defect structures. The fabricated MQWs exhibited high photoluminescence intensity because of the reduction in surface recombination with high nitrogen incorporation. Raman spectroscopy confirmed the presence of N-like local vibrational mode, and this was attributed to the presence of phase separation in GaAsN alloys. Rapid thermal annealing improved photoluminescence intensity by 100-fold and substantially reduced full width at half maximum because of MQW homogenization. These results evidence the favorable crystal interface of GaAs 0.978 N 0.022 alloys. Hence, GaAs 0.978 N 0.022 /GaAs MQWs grown under high pressure might be useful in fabricating optoelectronic devices.

Journal of Luminescence, 2020

Epitaxial growth of III-V heterostructures on non-native substrates such as Silicon (Si) or Germa... more Epitaxial growth of III-V heterostructures on non-native substrates such as Silicon (Si) or Germanium (Ge) is one of the promising research topics for the last two decades. The interface between polar III-V semiconductors and non-polar substrates (Si or Ge) plays a crucial role in monolithic integration. However, there is an anticipation of epitaxial GaAs growth on Ge substrate because of the lower mismatch of lattice constants and thermal expansion coefficients between them. Therefore, the high-quality growth of III-V semiconductor heterostructures on Ge substrates would overcome the impediment to Si-photonics, where the monolithic integration of optoelectronic device structures can be done using a Ge graded layer on Si. Here, we have explored the epitaxial growth of multi-layer InGaAs/GaAs quantum dot heterostructures on Ge substrates and compared the optical and structural properties with the QDs grown on GaAs substrate. The optical properties of all samples are investigated with the help of photoluminescence (PL) and time-resolved photoluminescence (TRPL), whereas the morphology of the QDs is observed through cross-sectional transmission electron microscopy (XTEM) images. An enhancement in the optical characteristics (PL peak wavelength, activation energy, carrier lifetime) is found for the QDs grown on Ge substrate with the super-lattice buffer (SLB) layer. The minimization of defects and dislocations in the heterostructure is also realized for the structure with the SLB layer. Furthermore, a twofold enhancement in PL intensity and 24 meV increment in activation energy is achieved through ex-situ H À ion-implantation, which approached the values obtained for the QD heterostructure grown on GaAs substrate.

Journal of Alloys and Compounds

Quantum Dots and Nanostructures: Synthesis, Characterization, and Modeling XII, 2015

Materials Science in Semiconductor Processing, 2020

It is already established that Poole-Frenkel (PF) transport is the dominant method of current tra... more It is already established that Poole-Frenkel (PF) transport is the dominant method of current transport in goldcatalyzed, Vapor-Liquid-Solid (VLS) grown, intrinsic silicon nanowires. However, this is contrary to common knowledge in the field. PF transport is often used to model the current-voltage (IV) relationship of materials without long-range order. In this study, the physical nature of the coulomb traps responsible for PF transport in VLS grown silicon nanowires has been investigated. It has been found that, VLS grown, single crystal silicon nanowires have small regions (<25 nm 2) of crystallographic misorientation throughout their volume. This, along with the twin boundaries found in the analysis, can periodically trap and detrap charge carriers traversing between the metal contacts on silicon nanowires. It is proposed that the omnipresence of these defects in the channel region to be the origin of PF transport in VLS grown silicon nanowires.

Materials Research Bulletin, 2017

Abstract GaAs 1−x N x /GaAs multiple quantum wells (MQWs) were grown on GaAs(001) substrates thro... more Abstract GaAs 1−x N x /GaAs multiple quantum wells (MQWs) were grown on GaAs(001) substrates through solid-source molecular beam epitaxy under various nitrogen background pressures (NBPs), and the crystal quality at the interface of GaAs 1−x N x and GaAs was investigated. X-ray diffraction and electron microscopy confirmed the low interface roughness of MQWs grown at a NBP of 5 × 10 −6 Torr. Surface morphology measurements revealed a smooth surface without whisker-like defect structures. The fabricated MQWs exhibited high photoluminescence intensity because of the reduction in surface recombination with high nitrogen incorporation. Raman spectroscopy confirmed the presence of N-like local vibrational mode, and this was attributed to the presence of phase separation in GaAsN alloys. Rapid thermal annealing improved photoluminescence intensity by 100-fold and substantially reduced full width at half maximum because of MQW homogenization. These results evidence the favorable crystal interface of GaAs 0.978 N 0.022 alloys. Hence, GaAs 0.978 N 0.022 /GaAs MQWs grown under high pressure might be useful in fabricating optoelectronic devices.

Journal of Luminescence, 2020

Epitaxial growth of III-V heterostructures on non-native substrates such as Silicon (Si) or Germa... more Epitaxial growth of III-V heterostructures on non-native substrates such as Silicon (Si) or Germanium (Ge) is one of the promising research topics for the last two decades. The interface between polar III-V semiconductors and non-polar substrates (Si or Ge) plays a crucial role in monolithic integration. However, there is an anticipation of epitaxial GaAs growth on Ge substrate because of the lower mismatch of lattice constants and thermal expansion coefficients between them. Therefore, the high-quality growth of III-V semiconductor heterostructures on Ge substrates would overcome the impediment to Si-photonics, where the monolithic integration of optoelectronic device structures can be done using a Ge graded layer on Si. Here, we have explored the epitaxial growth of multi-layer InGaAs/GaAs quantum dot heterostructures on Ge substrates and compared the optical and structural properties with the QDs grown on GaAs substrate. The optical properties of all samples are investigated with the help of photoluminescence (PL) and time-resolved photoluminescence (TRPL), whereas the morphology of the QDs is observed through cross-sectional transmission electron microscopy (XTEM) images. An enhancement in the optical characteristics (PL peak wavelength, activation energy, carrier lifetime) is found for the QDs grown on Ge substrate with the super-lattice buffer (SLB) layer. The minimization of defects and dislocations in the heterostructure is also realized for the structure with the SLB layer. Furthermore, a twofold enhancement in PL intensity and 24 meV increment in activation energy is achieved through ex-situ H À ion-implantation, which approached the values obtained for the QD heterostructure grown on GaAs substrate.

Journal of Alloys and Compounds

Quantum Dots and Nanostructures: Synthesis, Characterization, and Modeling XII, 2015