Review on III-V semiconductor single nanowire-based room temperature infrared photodetectors

Recently, III-V semiconductor nanowires have been widely explored as promising candidates for high-performance photodetectors due to their one-dimensional morphology, direct and tunable bandgap, as well as unique optical and electrical properties. Here, the recent development of III-V semiconductor-based single nanowire photodetectors for infrared photodetection is reviewed and compared, including material synthesis, representative types (under different operation principles and novel concepts), and device performance, as well as their challenges and future perspective

Dhyani, Veerendra Georgiev, Yordan M. Gangnaik, Anushka S. Biswas, Subhajit Holmes, Justin D. Das, Amit K. Ray, Samit K. Das, Samaresh

Here, we report the observation of negative photoconductance (NPC) effect in highly arsenic-doped germanium nanowires (Ge NWs) for the infrared light. NPC was studied by light-assisted Kelvin probe force microscopy, which shows the depletion of carriers in n-Ge NWs in the presence of infrared light. The trapping of photocarriers leads to high recombination of carriers in the presence of light, which is dominant in the n-type devices. Furthermore, a carrier trapping model was used to investigate the trapping and detrapping phenomena and it was observed that the NPC in n-Ge occurred, because of the fast trapping of mobile charge carriers by interfacial states. The performance of n-type devices was compared with p-type NW detectors, which shows the conventional positive photoconductive behavior with high gain of 104. The observed results can be used to study the application of Ge NWs for various optoelectronic applications involving light tunable memory device applications

Gallium Arsenide Based Metal-Semiconductor-Metal Devices and Detectors

Each year the creation and refinement of new material growth techniques give rise to novel material systems for electronic device exploration. A metal-semiconductor-metal (MSM) device is the simplest electronic device possible, consisting of two metal contacts on a semiconducting channel. Despite their simplicity, these devices can operate as high performance detectors as well as enable rapid characterization of novel electronic materials. This thesis will discuss the fabrication and characterization of MSM devices on a two-dimensional electron hole gas (2DEHG) and GaAs-based nanowires. 2DEHG structures consist of two spatial separated quantum wells of opposite charge. These devices exhibit a high-speed photo-response, a two plateau varactor response and give rise to several unexplained photoluminescence peaks. GaAs-based nanowire MSMs offer the opportunity to fabricate many of the well known bulk III-V semiconductor devices on the nanoscale. Accomplishing this requires quality ohmic contacts. Several fabrication methods to create ohmic contacts on GaAs nanowires are described, as well as characterization of the light response of these devices and results demonstrating ambipolar transport in a wide bandgap material. The devices offer promise as high speed on-chip interconnects for digital circuits.Ph.D., Electrical Engineering -- Drexel University, 201

Miniaturized Silicon Photodetectors

Silicon (Si) technologies provide an excellent platform for the design of microsystems where photonic and microelectronic functionalities are monolithically integrated on the same substrate. In recent years, a variety of passive and active Si photonic devices have been developed, and among them, photodetectors have attracted particular interest from the scientific community. Si photodiodes are typically designed to operate at visible wavelengths, but, unfortunately, their employment in the infrared (IR) range is limited due to the neglectable Si absorption over 1100 nm, even though the use of germanium (Ge) grown on Si has historically allowed operations to be extended up to 1550 nm. In recent years, significant progress has been achieved both by improving the performance of Si-based photodetectors in the visible range and by extending their operation to infrared wavelengths. Near-infrared (NIR) SiGe photodetectors have been demonstrated to have a “zero change” CMOS process flow, while the investigation of new effects and structures has shown that an all-Si approach could be a viable option to construct devices comparable with Ge technology. In addition, the capability to integrate new emerging 2D and 3D materials with Si, together with the capability of manufacturing devices at the nanometric scale, has led to the development of new device families with unexpected performance. Accordingly, this Special Issue of Micromachines seeks to showcase research papers, short communications, and review articles that show the most recent advances in the field of silicon photodetectors and their respective applications

Group III-Nitrides and Their Hybrid Structures for Next-Generation Photodetectors

In the last few decades, there has been a phenomenal rise and evolution in the field of III–Nitride semiconductors for optoelectronic applications such as lasers, sensors and detectors. However, certain hurdles still remain in the path of designing high-performance photodetectors (PDs) based on III-Nitride semiconductors considering their device performance. Recently, a lot of progress has been achieved in devices based on the high quality epilayers grown by molecular beam epitaxy (MBE). Being an ultra-high vacuum environment based-technique, MBE has enabled the realization of high-quality and highly efficient PDs which have exhibited competitive figures of merit to that of the commercial PDs. Moreover, by combining the novel properties of 2D materials with MBE-grown III-Nitrides, devices with enhanced functionalities have been realized which would pave a way towards the next-generation photonics. In the current chapter, the basic concepts about photodetection have been presented in detail, followed by a discussion on the basic properties of the III-Nitride semiconductors, and the recent advancements in the field of MBE-grown III-Nitrides-based PDs, with an emphasis on their hybrid structures. Finally, an outlook has been provided highlighting the present shortcomings as well as the unresolved issues associated with the present-day devices in this emerging field of research

Hot-carrier extraction in nanowires

A hot-carrier solar cell aims to generate power from energetic, photoexcited, charge carriers, so called hot carriers, in order to reach higher conversion efficiencies than current solar cell technology.Creating a hot-carrier solar cell has proven challenging for two main reasons: hot carriers lose their energy very quickly, and they need to be extracted over distances of a few hundrednanometers via energy selective filters.Semiconducting III-V nanowires offer high flexibility and control in heterostructure growth, enabling the realisation of numerous types of energy filters, in combination with promising properties such as reduced thermal conductivity, increased hot-carrier temperatures, and various possibilities to tune optical absorption.This thesis aims to expand current knowledge of how to optimally design devices for hot-carrier extraction in practice.Specifically, three experimental papers (I-III) study the generation of electrical power by extracting charge carriers across energy selective filters within single semiconducting nanowires. The fourth paper (IV) reviews current literature relating to hot carriers in nanowires.The experiments are based on InAs nanowires with epitaxially defined heterostructures of InP or InAsP that form energy filters. Charge carrier extraction is studied by three different means: excitation of a non-equilibrium distribution by optical or electron-beam exposure, or the generation of an equilibrium distribution by heat. In Papers I and II, hot-carrier extraction is spatially resolved over a rectangular InP barrier. Paper I uses the high spatial resolution of an electron beam, while Paper II studies the operation of a similar devices under highly focused optical excitation. Both papers observe hot-carrier extraction around the barrier. The mechanism for extraction is better understood and valuable input for the future design of hot-carrier photovoltaic devices is extracted, such as hot-electron diffusion lengths on the order of a few hundred nanometers. Paper III studies thermoelectric power generation in a nonlinear transport regime of a ramp-shaped potential barrier, realised by gradually changing x in InAs_xP_(1-x). It is observed that fill factor, and thus maximum output power, can be tuned beyond the linear response limits. This opens up a new door of possibility for tuning the performance of both thermoelectric and hot-carrier photovoltaic systems

Substrate-Dependent Photodetection with Functional Nanomaterials

Dielektrische Einflüsse auf nanostrukturierte Materialien sind bekannt, jedoch in Bezug auf die Geschwindigkeit der Photodetektion noch kaum erforscht. Diese Arbeit behandelt den Einfluss des Substrates auf die Schaltgeschwindigkeit funktioneller Nanomaterialien am Beispiel von CdSe Quantenpunkten und WSe2 Kristallen und berücksichtigt dabei sowohl die Zeit, die bis zum Erreichen des Gleichgewichtszustandes benötigt wird, als auch das Verhalten des Detektors im instationären (Nicht-Gleichgewichts) Zustand. Ersteres kann Informationen bezüglich des geschwindigkeitsbestimmenden Faktors des Photodetektors liefern, während letzteres die im Detektor vorliegenden Abklingmechanismen aufzeigen kann.Dielectric influences on nanostructured materials are widely known but hardly explored in terms of the speed of photodetection. This work deals with the influence of the substrate on the speed of response of functional nanomaterials considering CdSe quantum dots and WSe2 crystals as examples, and takes into account both the time required to reach the steady state and the performance of the detector in the transient (non-steady state) condition. The former can provide information regarding the speed limiting factor of the photodetector, while the latter can reveal the decay mechanisms present in the detector

Electronic Nanodevices

The start of high-volume production of field-effect transistors with a feature size below 100 nm at the end of the 20th century signaled the transition from microelectronics to nanoelectronics. Since then, downscaling in the semiconductor industry has continued until the recent development of sub-10 nm technologies. The new phenomena and issues as well as the technological challenges of the fabrication and manipulation at the nanoscale have spurred an intense theoretical and experimental research activity. New device structures, operating principles, materials, and measurement techniques have emerged, and new approaches to electronic transport and device modeling have become necessary. Examples are the introduction of vertical MOSFETs in addition to the planar ones to enable the multi-gate approach as well as the development of new tunneling, high-electron mobility, and single-electron devices. The search for new materials such as nanowires, nanotubes, and 2D materials for the transistor channel, dielectrics, and interconnects has been part of the process. New electronic devices, often consisting of nanoscale heterojunctions, have been developed for light emission, transmission, and detection in optoelectronic and photonic systems, as well for new chemical, biological, and environmental sensors. This Special Issue focuses on the design, fabrication, modeling, and demonstration of nanodevices for electronic, optoelectronic, and sensing applications