Sourav Adhikary

Bio: Sourav Adhikary is an academic researcher from Indian Institute of Technology Bombay. The author has contributed to research in topics: Quantum dot & Heterojunction. The author has an hindex of 16, co-authored 40 publications receiving 739 citations. Previous affiliations of Sourav Adhikary include Northwestern University & VIT University.

High performance bias-selectable three-color Short-wave/Mid-wave/Long-wave Infrared Photodetectors based on Type-II InAs/GaSb/AlSb superlattices

Abstract: We propose a new approach in device architecture to realize bias-selectable three-color shortwave-midwave-longwave infrared photodetectors based on InAs/GaSb/AlSb type-II superlattices. The effect of conduction band off-set and different doping levels between two absorption layers are employed to control the turn-on voltage for individual channels. The optimization of these parameters leads to a successful separation of operation regimes; we demonstrate experimentally three-color photodiodes without using additional terminal contacts. As the applied bias voltage varies, the photodiodes exhibit sequentially the behavior of three different colors, corresponding to the bandgap of three absorbers. Well defined cut-offs and high quantum efficiency in each channel are achieved. Such all-in-one devices also provide the versatility of working as single or dual-band photodetectors at high operating temperature. With this design, by retaining the simplicity in device fabrication, this demonstration opens the prospect for three-color infrared imaging.

Multi-stack InAs/InGaAs Sub-monolayer Quantum Dots Infrared Photodetectors

Abstract: We report on the design and performance of multi-stack InAs/InGaAs sub-monolayer (SML) quantum dots (QD) based infrared photodetectors (SML-QDIP). SML-QDIPs are grown with the number of stacks varied from 2 to 6. From detailed radiometric characterization, it is determined that the sample with 4 SML stacks has the best performance. The s-to-p (s/p) polarized spectral response ratio of this device is measured to be 21.7%, which is significantly higher than conventional Stranski-Krastanov quantum dots (∼13%) and quantum wells (∼2.8%). This result makes the SML-QDIP an attractive candidate in applications that require normal incidence.

High-performance, long-wave (∼10.2 μm) InGaAs/GaAs quantum dot infrared photodetector with quaternary In0.21Al0.21Ga0.58As capping

Abstract: A high-performance InGaAs/GaAs vertical quantum dot infrared photodetector (QDIP) with combined barrier of quaternary In0.21Al0.21Ga0.58As and GaAs was investigated in this study. A dominant long wavelength (∼10.2 μm) response was observed from the device. The device demonstrates large responsivity (2.16 A/W) with narrow spectral-width (Δλ/λ ∼0.14) and high detectivity (1.01 × 1011 cm Hz1/2/W at 0.3 V) at 10.2 μm at 77 K. In addition, the device has also produced a detectivity in the order of 6.4 × 1010 cm Hz1/2/W at 100 K at a bias of 0.2 V, indicating its suitability for high-temperature operations.

Sub-monolayer quantum dots in confinement enhanced dots-in-a-well heterostructure

Abstract: We have investigated optical properties and device performance of sub-monolayer quantum dots infrared photodetector with confinement enhancing (CE) barrier and compared with conventional Stranski-Krastanov quantum dots with a similar design. This quantum dots-in-a-well structure with CE barrier enables higher quantum confinement and increased absorption efficiency due to stronger overlap of wavefunctions between the ground state and the excited state. Normal incidence photoresponse peak is obtained at 7.5 μm with a detectivity of 1.2 × 1011 cm Hz1/2 W−1 and responsivity of 0.5 A/W (77 K, 0.4 V, f/2 optics). Using photoluminescence and spectral response measurements, the bandstructure of the samples were deduced semi-empirically.

A Review on Organic–Inorganic Halide Perovskite Photodetectors: Device Engineering and Fundamental Physics

Abstract: The last eight years (2009-2017) have seen an explosive growth of interest in organic-inorganic halide perovskites in the research communities of photovoltaics and light-emitting diodes. In addition, recent advancements have demonstrated that this type of perovskite has a great potential in the technology of light-signal detection with a comparable performance to commercially available crystalline Si and III-V photodetectors. The contemporary growth of state-of-the-art multifunctional perovskites in the field of light-signal detection has benefited from its outstanding intrinsic optoelectronic properties, including photoinduced polarization, high drift mobilities, and effective charge collection, which are excellent for this application. Photoactive perovskite semiconductors combine effective light absorption, allowing detection of a wide range of electromagnetic waves from ultraviolet and visible, to the near-infrared region, with low-cost solution processability and good photon yield. This class of semiconductor might empower breakthrough photodetector technology in the field of imaging, optical communications, and biomedical sensing. Therefore, here, the focus is specifically on the critical understanding of materials synthesis, design, and engineering for the next-stage development of perovskite photodetectors and highlighting the current challenges in the field, which need to be further studied in the future.

Multifunctional Skin-Inspired Flexible Sensor Systems for Wearable Electronics

Abstract: DOI: 10.1002/admt.201800628 applications (e.g., soft robotics, medical devices).[1–6] Despite state-of-the-art bulkbased planar integrated-circuit devices, their rigid and brittle nature gives rise to the incompatibility with curvilinear and soft human bodies, restricting the development of newborn human-friendly interactive electronics. In contrast, the bendable and flexible wearable electronics could be conformally attached onto human bodies almost without discomfort and succeed in performing a great deal of sensing functionalities. Realization of such promising goals requires the flexible sensor platforms provided with crucial characteristics of light weight, ultrathinness, superior flexibility, stretchability, high sensitivity as well as rapid response.[7–10] Inspired by the perceptive features of human skins, the wearable sensor systems are capable of acquiring abundant information from the external environment with the assistance of sensing modules, such as pressure sensors, strain sensors, temperature sensors, etc.[11] A typical example is their application in prosthetics that could afford the capacity to perceive touch or temperature for the disabled.[12] Additionally, the wearable sensor systems are able to identify physical or chemical signals produced by the human body, providing promising opportunities to evaluate health states.[5,13–15] Conventional skin-like sensor platforms primarily comprise one or two sensing modules, data processing units, and power supplies. Their unitary functionality, however, cannot satisfy the increasing demands of IoTs. Recently, the rapid advances in novel sensing materials, fabrication strategies, and innovative electronic constitution contribute to the development of versatile integration of multimodal sensors, which could synchronously distinguish diverse stimuli from the complex environment and monitor multiple vital signs from the human body.[16,17] In spite of several attempts done in terms of such multimodal sensor systems, one of the cumbersome issues originates from the crosscoupling effect among different categories of signals simultaneously generated by various sensors. Furthermore, the skin-like multiple sensor systems usually suffer from the limited number of repeated use, resulting in their high use-cost. The development of separable versatile devices may address this issue with one layer realized by costeffective materials and fabrication manners for disposable use and the other composed of relatively expensive components for repeatable applications.[18] Additionally, the multiple bending or Skin-inspired wearable devices hold great potentials in the next generation of smart portable electronics owing to their intriguing applications in healthcare monitoring, soft robotics, artificial intelligence, and human–machine interfaces. Despite tremendous research efforts dedicated to judiciously tailoring wearable devices in terms of their thickness, portability, flexibility, bendability as well as stretchability, the emerging Internet of Things demand the skininterfaced flexible systems to be endowed with additional functionalities with the capability of mimicking skin-like perception and beyond. This review covers and highlights the latest advances of burgeoning multifunctional wearable electronics, primarily including versatile multimodal sensor systems, self-healing material-based devices, and self-powered flexible sensors. To render the penetration of human-interactive devices into global markets and households, economical manufacturing techniques are crucial to achieve large-scale flexible systems with high-throughput capability. The booming innovations in this research field will push the scientific community forward and benefit human beings in the near future.

Atomically thin noble metal dichalcogenide: a broadband mid-infrared semiconductor.

Abstract: The interest in mid-infrared technologies surrounds plenty of important optoelectronic applications ranging from optical communications, biomedical imaging to night vision cameras, and so on. Although narrow bandgap semiconductors, such as Mercury Cadmium Telluride and Indium Antimonide, and quantum superlattices based on inter-subband transitions in wide bandgap semiconductors, have been employed for mid-infrared applications, it remains a daunting challenge to search for other materials that possess suitable bandgaps in this wavelength range. Here, we demonstrate experimentally for the first time that two-dimensional (2D) atomically thin PtSe2 has a variable bandgap in the mid-infrared via layer and defect engineering. Here, we show that bilayer PtSe2 combined with defects modulation possesses strong light absorption in the mid-infrared region, and we realize a mid-infrared photoconductive detector operating in a broadband mid-infrared range. Our results pave the way for atomically thin 2D noble metal dichalcogenides to be employed in high-performance mid-infrared optoelectronic devices.

Polarization-resolved black phosphorus/molybdenum disulfide mid-wave infrared photodiodes with high detectivity at room temperature

Abstract: Infrared photodetectors are currently subject to a rapidly expanding application space, with an increasing demand for compact, sensitive and inexpensive detectors. Despite continued advancement, technological factors limit the widespread usage of such detectors, specifically, the need for cooling and the high costs associated with processing of iii–v/ii–vi semiconductors. Here, black phosphorous (bP)/MoS2 heterojunction photodiodes are explored as mid-wave infrared (MWIR) detectors. Although previous studies have demonstrated photodiodes using bP, here we significantly improve the performance, showing that such devices can be competitive with conventional MWIR photodetectors. By optimizing the device structure and light management, we demonstrate a two-terminal device that achieves room-temperature external quantum efficiencies (ηe) of 35% and specific detectivities (D*) as high as 1.1 × 1010 cm Hz1/2 W−1 in the MWIR region. Furthermore, by leveraging the anisotropic optical properties of bP we demonstrate the first bias-selectable polarization-resolved photodetector that operates without the need for external optics.

Recent advances in two-dimensional-material-based sensing technology toward health and environmental monitoring applications

Abstract: Monitoring harmful and toxic chemicals, gases, microorganisms, and radiation has been a challenge to the scientific community for the betterment of human health and environment. Two-dimensional (2D)-material-based sensors are highly efficient and compatible with modern fabrication technology, which yield data that can be proficiently used for health and environmental monitoring. Graphene and its oxides, black phosphorus (BP), transition metal dichalcogenides (TMDCs), metal oxides, and other 2D nanomaterials have demonstrated properties that have been alluring for the manufacture of highly sensitive sensors due to their unique material properties arising from their inherent structures. This review summarizes the properties of 2D nanomaterials that can provide a platform to develop high-performance sensors. In this review, we have also discussed the advances made in the field of infrared photodetectors and electrochemical sensors and how the structural properties of 2D nanomaterials affect sensitivity and performance. Further, this review highlights 2D-nanomaterial-based electrochemical sensors that can be used to check for contaminations from heavy metals, organic/inorganic compounds, poisonous gases, pesticides, bacteria, antibiotics, etc., in water or air, which are severe risks to human wellbeing as well as the environment. Moreover, the limitations, future prospects, and challenges for the development of sensors based on 2D materials are also discussed for future advancements.