Plasmonic Photodetectors Research Articles

On-Chip Ge Photodetector Efficiency Enhancement by Local Laser-Induced Crystallization.

Metal-semiconductor-metal plasmonic nanostructures enable both on-chip efficient manipulation and ultrafast photodetection of strongly confined modes by enhancing local electrostatic and optical fields. The latter is achieved by making use of nanostructured thin-film germanium (Ge) plasmonic-waveguide photodetectors. While their sizes and locations can be accurately controlled during the nanofabrication, the detector efficiencies are significantly reduced due to deposited Ge amorphous nature. We demonstrate that the efficiency of waveguide-integrated Ge plasmonic photodetectors can be increased significantly (more than 2 orders of magnitude) by spatially controlled laser-induced Ge crystallization. We investigate both free-space and waveguide-integrated Ge photodetectors subjected to 800 nm laser treatment, monitoring the degree of crystallization with Raman spectroscopy, and demonstrate the efficiency enhancement by detecting the telecom radiation. The demonstrated local postprocessing technique can be utilized in various nanophotonic devices for efficient and ultrafast on-chip radiation monitoring and detection, offering significantly improved detector characteristics without jeopardizing the performance of other components.

Hot electron photoemission in metal–semiconductor structures aided by resonance tunneling

Enhancement of the surface photoemission from metal into semiconductor by resonance tunneling of photoexcited electrons through (quasi-) discrete level in quantum well, located within Schottky barrier of the metal–semiconductor interface, is studied theoretically taking into account the difference between the electron masses in metal and semiconductor. It is shown, in particular, that resonance tunneling through the discrete level can lead to the redshift of the threshold wavelength of surface photoeffect, higher slope linear growth in photocurrent near the threshold (in contrast to quadratic growth, i.e., Fowler's law), and the possibility to increase substantially the photoemission efficiency similarly to recent experimental results on hot carrier generation in plasmonic structures with a discrete energy level at metal interface. The difference in the effective masses is shown to significantly affect the results. Double-barrier tunneling structures with resonant tunneling may become attractive for applications in photochemistry and in plasmonic photodetectors in near IR and middle IR regions of the spectrum.

Patterning of transition metal dichalcogenides catalyzed by surface plasmons with atomic precision

Summary Plasmon-induced charge transfer has drawn considerable interests and spurred rapid developments of photovoltaics and photocatalysis. Various plasmonic metal/transition metal dichalcogenide (TMD) heterostructures have been developed to promote charge separation. For plasmon-induced catalysis, the transformation of TMDs is rare, and the erosion of TMDs has not yet been reported. Here, we report the etching of two-dimensional TMDs by planar surface plasmon polaritons (SPPs). We found that SPPs can etch various TMDs into desired layers and lateral size through controlling the light power and incident direction. In aqueous media, the strong plasmonic coupling at Au/MoS2 interface generates holes in the valence band of MoS2 that can weaken its interlayer interaction. As a synergistic effect, the plasmonic hot electrons produce oxidizing H2O2 to dissolve MoS2 from the top layers. Our results provide a new perspective for understanding the plasmonic coupling at metal-TMD interfaces and a reliable route toward fabricating well-defined TMDs.

Engineering plasmonic hot carrier dynamics toward efficient photodetection

Nonradiative decay of surface plasmons (SPs) is usually considered an unwanted process. However, recent studies have proven that hot carriers generated from nonradiative SP decay can be used for photodetection that circumvents the bandgap limitation in semiconductors. The major problem plaguing the plasmonic hot carrier photodetectors stems from the low quantum efficiency. In this review, we discuss recent progress of engineering plasmonic hot carrier dynamics and describe a host of plasmon-enhanced photodetectors, including optical antenna-based photodetectors, planar photodetectors, photodetectors coupled with 2D materials, functionalized photodetectors, photodetectors for integrated nanophotonics, and hot-hole photodetectors. Finally, we herein highlight some new directions in the plasmonic photodetection.

Surface plasmon enhanced GeSn photodetectors operating at 2 µm.

Au-hole array and Au-GeSn grating structures were designed and incorporated in GeSn metal-semiconductor-metal (MSM) photodetectors for enhanced photo detection at 2 µm. Both plasmonic structures are beneficial for effective optical confinement near the surface due to surface plasmon resonance (SPR), contributing to an enhanced responsivity. The responsivity enhancement for Au hole-array structure is insensitive to the polarization direction, while the enhancement for Au-GeSn grating structure depends on the polarization direction. The responsivity for GeSn photodetector with Au hole-array structure has ∼50% reinforcement compared with reference photodetector. On the other hand, Au-GeSn grating structure benefits a 3× enhanced responsivity of 0.455 A/W at 1.5V under TM-polarized illumination. The achieved responsivity is among the highest values for GeSn photodetectors operating at 2 µm. The plasmonic GeSn photodetectors in this work offer an alternative solution for high-efficiency photo detection, manifesting their great potentials as candidates for 2 µm optical communication and other emerging applications.

Investigating the impact of metallic nanoparticles on performance of nanowire‐based plasmonic photodetectors

In this study, the authors have theoretically investigated the effects of metallic nanoparticles (NPs) on the performance of nanowire-based plasmonic photodetectors. For this goal, they propose a novel structure for plasmonic photodetectors in which the metallic NPs are deposited on a semiconductor nanowire sandwiched between two ohmic contacts. To calculate the eigenstates of the system, they have solved the Schrodinger equation for the nanowire in a nanostructure system with metallic NPs. Obtaining the system's eigenstates, the nanowires absorption coefficient, dielectric constant, and refractive index have been calculated. Also, the dependency of these parameters on the input wavelength has discussed. Besides, to find out the impact of metallic NPs, they have calculated the current of the system. They also have made a comparison of the system's responsivity in the simple condition (where there are no NPs effects) and the hybrid condition, in which the effects of NPs are also be considered. In fact, the effects of the NPs in the enhancement of the electrical field, and their role in the scattering of the field are the main fields of studies in this work.

Graphene-on-plasmonic slot waveguide photodetector

Integrated silicon-based plasmonic photodetectors have attracted more and more attention recently, due to their potential applications in THz bandwidth. In this paper, by utilizing a simplified two-step lithography process, the photoconductive detector is fabricated with the core structure of plasmonic slot waveguide in two symmetric metallic slabs as microwave electrodes to integrate with mechanically exfoliated graphene. The 3-dB bandwidth of the graphene-on-plasmonic slot waveguide photodetector is exceeded 120 GHz under the theoretical calculation, and the measured bandwidth is still beyond 70 GHz due to the lack of larger-bandwidth equipment. High-speed data reception is demonstrated for 72 Gbit/s NRZ and 64 Gbit/s PAM-4 signals with a BER below 15% soft-decision FEC threshold. Based on the enhanced interactions of light and graphene induced by the subwavelength confinement from the plasmonic structure, the responsivity of 0.13 A/W is achieved under the condition of the 7-μm long detection zone and the 0.4-V bias voltage. With the advantages of ultra-compact, high-speed, large-bandwidth and compatible with the CMOS process, our photodetector has the potential to be used in high-speed optical interconnection, terahertz transmission and terahertz communication.

Hot-Hole versus Hot-Electron Transport at Cu/GaN Heterojunction Interfaces.

Among all plasmonic metals, copper (Cu) has the greatest potential for realizing optoelectronic and photochemical hot-carrier devices, thanks to its CMOS compatibility and outstanding catalytic properties. Yet, relative to gold (Au) or silver (Ag), Cu has rarely been studied and the fundamental properties of its photoexcited hot carriers are not well understood. Here, we demonstrate that Cu nanoantennas on p-type gallium nitride (p-GaN) enable hot-hole-driven photodetection across the visible spectrum. Importantly, we combine experimental measurements of the internal quantum efficiency (IQE) with ab initio theoretical modeling to clarify the competing roles of hot-carrier energy and mean-free path on the performance of hot-hole devices above and below the interband threshold of the metal. We also examine Cu-based plasmonic photodetectors on corresponding n-type GaN substrates that operate via the collection of hot electrons. By comparing hot hole and hot electron photodetectors that employ the same metal/semiconductor interface (Cu/GaN), we further elucidate the relative advantages and limitations of these complementary plasmonic systems. In particular, we find that harnessing hot holes with p-type semiconductors is a promising strategy for plasmon-driven photodetection across the visible and ultraviolet regimes. Given the technological relevance of Cu and the fundamental insights provided by our combined experimental and theoretical approach, we anticipate that our studies will have a broad impact on the design of hot-carrier optoelectronic devices and plasmon-driven photocatalytic systems.

Au grating on SiC substrate: simulation of high performance plasmonic Schottky barrier photodetector in visible and NIR regions

Plasmonically enhanced light absorption in Schottky barrier photodetectors (PDs) can be achieved by engineering metallic nanostructures. In this context, gold (Au) gratings on titanium (Ti)/silicon carbide (SiC) based Schottky barrier is proposed in this work for photodetection application. Further, the effects of various grating parameters and incident angle on absorbance are demonstrated. The grating based structure is able to provide ~85% incident light absorption leading to a significantly high responsivity value as compared with that of conventional (without metallic grating) structure. High unbiased responsivity values of 4.396 mA W−1 and 2.496 mA W−1 are obtained for Au/Ti/6H-SiC Schottky barrier PD at wavelengths of 694.5 nm and 1035 nm, respectively based on Fowler’s model. In view of advanced properties of SiC, the present work will open new opportunities for plasmonic PDs based on SiC platform.

Reconfigurable Surface Plasmon Resonance Photodetector with a MEMS Deformable Cantilever

Plasmonic photodetectors have many useful characteristics, such as wavelength- or polarization-specific photodetection. Although reconfigurable plasmonic structures have been intensively studied, r...

Applicability of Plasmonic Photodetectors with Dynamic Reconfiguration of Detectable Wavelength for Spectroscopy

Applicability of Plasmonic Photodetectors with Dynamic Reconfiguration of Detectable Wavelength for Spectroscopy

Infrared plasmonic photodetectors: the emergence of high photon yield toroidal metadevices

Plasmon excitations in metallic nanostructures can decay directly into dynamic electron–hole pairs, exploitable for photocurrent generation. This approach has extensively been employed to develop nanoplasmonic light-sensing devices with significant responsivity and quantum efficiency. Among the devices, infrared plasmonic photodetectors have gained particular interest for their wide range of technological applications, including spectroscopy, biosensing, and surveillance. This Review discusses the fundamentals, recent advances, and trending mechanisms in the understanding and applications of plasmon-enhanced photocurrent generation in nanostructures across the infrared spectrum. By highlighting and comparing the developed techniques, we demonstrate the newly introduced directions toward achieving high photon yield infrared plasmonic photodetection tools. As a promising concept in modern metaphotonics, we present the emergence of toroidal meta-atoms as plasmon-induced carrier generators with unconventionally exquisite properties for designing advanced, rapid, and next-generation plasmonic photodetectors with significantly high responsivity and photocurrent.

High-bandwidth and high-responsivity waveguide-integrated plasmonic germanium photodetector

Here we propose a waveguide-integrated germanium plasmonic photodetector that is based on a long-range dielectric-loaded surface plasmon polariton waveguide configuration. As this configuration ensures a long propagation distance, i.e., small absorption into metal, and a good mode field confinement, i.e., high interaction of the electric field with a germanium material, it is perfect for a realization of plasmonic germanium photodetectors. Such a photodetector even without optimization provides a responsivity exceeding 1 A/W for both wavelengths of 1310 nm and 1550 nm. To achieve such a responsivity, only a 5 {\mu}m-long waveguide is required for 1310 nm and 30 {\mu}m-long for 1550 nm. With optimization this value can be highly improved. In the proposed arrangement a metal stripe simultaneously supports a propagating mode and serves as one of the electrodes, while the second electrode is located a short distance from the waveguide. As a propagating mode is tightly confined to the germanium ridge, the external electrode can be placed very close to the waveguide without disturbing it. As such, the distance between electrodes can be smaller than 350 nm which allows one to achieve a bandwidth exceeding 100 GHz. However, as most of the carriers are generated inside a distance of 100 nm from a stripe, a bandwidth exceeding 150 GHz can be achieved for a bias voltage of -4 V.

Low‐Dimensional Plasmonic Photodetectors: Recent Progresses and Future Opportunities

Low‐Dimensional Plasmonic Photodetectors: Recent Progresses and Future Opportunities

Plasmonic hole-transport-layer enabled self-powered hybrid perovskite photodetector using a modified perovskite deposition method in ambient air

Herein, we report on an air-processed high performance self-powered hybrid perovskite (Pe) photodetector with plasmonic Silver nanoparticle (Ag NP) embedded hole-transport-layer (HTL), without the use of any electron-transporting layer (ETL). It is demonstrated that in the absence of ETL in the device, the Ag NPs embedded PEDOT:PSS HTL improves the photodetection performance significantly. We used a novel N2 gas assisted fast crystallization method for the deposition of perovskite film in ambient condition to form uniform Pe layer as compared to the nonuniform film obtained in conventional deposition method. The Pe film on Ag NPs embedded PEDOT:PSS layer shows enhanced optical absorption in the UV–visible region due to the plasmonic absorption by the Ag NPs. At zero bias, the ETL-free Ag NPs-Pe hybrid device shows ∼45% enhanced responsivity and ∼3 times faster photoresponse compared to the pristine device. The enhancements in the performance of hybrid photodetector are attributed to plasmon-enhanced optical absorption and hot electron generation, as well as improvement in charge extraction and transport by Ag NPs, which are corroborated by steady-state and time-resolved photoluminescence measurements. Impedance analysis of the devices shows the reduced carrier transfer resistance of the hybrid device, which results in superior transport of photo-generated charge carriers. Direct evidence for the increase in the work function by ∼47 meV for Ag NPs doped PEDOT:PSS film is provided from the Kelvin probe force microscopy analysis. This increase in work function enables favorable band alignment with reduced energy barrier and a superior carrier transport resulting in improved photodetection performance for the hybrid device. Our results are significant for the development of high-performance, low-cost, ETL free plasmonic perovskite photodetectors for futuristic applications.

Generation of magnetoelectric photocurrents using toroidal resonances: a new class of infrared plasmonic photodetectors.

The detection of photons by plasmonic subwavelength devices underpins spectroscopy, low-power wavelength division multiplexing for short-distance optical communication, imaging, and time-gated distance measurements. In this work, we demonstrate infrared light-sensing using toroidal dipole-resonant plasmonic multipixel meta-atoms. As a key factor, the toroidal dipolar mode is an extremely localized electromagnetic excitation independent of the conventional multipoles. The exquisite behavior of this mode enables significant enhancements in the localized electromagnetic field and absorption cross-section, which boost the field confinement at the metal-dielectric interfaces. The proposed novel approach offers an advanced photodetection of the incident light based on substantial confinement of electromagnetic fields in a tiny spot, giving rise to the generation of hot carriers and a large photocurrent. Using both n- and p-type silicon (Si) substrates, we exploited the free-carrier absorption advantage of p-type Si to devise a high-responsivity device. Our findings show an unprecedented performance for infrared plasmonic photodetectors with low noises, high detectivity and remarkable internal quantum efficiency (IQE). Moreover, the tailored photodetection device provides a significant linear dynamic range of 46 dB and a fast operation speed. Our narrowband infrared light sensing photodevice offers a promising approach for further research studies over the optoelectronic and plasmonic tools and paves a viable route for low-dimensional photonic systems.

Plasmonic Photodetectors

Plasmonic photodetectors are attracting the attention of the photonics community. Plasmonics is attractive because metallic structures have the ability to confine light by coupling an electromagnetic wave to charged carrier oscillations at the surface of the metal. The wavelength of such oscillations can be much smaller than the corresponding light wavelength in vacuum. This enables the light-matter interaction on a deep subwavelength scale, which in turn allows for more compact and potentially higher speed devices. In this review, we discuss different types of photodetectors and ways in which plasmonics can be applied to them. We elucidate several plasmonic photodetector concepts/schemes and discuss the main physical principles behind their operation. Finally, we reflect on the characteristics of an “ideal” photodetector and propose a device that might be the perfect plasmonic detector.

Low‐Dimensional Plasmonic Photodetectors: Recent Progress and Future Opportunities

AbstractPlasmonic nanostructures can achieve subdiffraction‐limit light confinement with enhanced electric fields. By taking advantage of the light‐confinement effect, various plasmonic photodetectors that combine low‐dimensional (LD) semiconductor structures and plasmonic materials have recently demonstrated excellent plasmon‐enhanced device performance and attracted significant research interest. In this review, the state‐of‐the‐art progress in the development of various LD photodetectors with different plasmonic structures is briefly surveyed, in order to provide a clear picture of related fabrication methods, leading to maximized plasmonic enhancement. The fundamentals of localized surface‐plasmon resonance and plasmonic hot electrons are first introduced, followed by a summary of several prototypical LD photodetectors enhanced by metal nanoparticles (NPs), including noble‐metal NPs, poor‐metal NPs, and some plasmonic doped‐semiconductor NPs. The recent achievement of the newly developed LD photodetectors propelled by plasmonic hot carriers is also highlighted. Finally, some challenges and issues that need to be resolved in this field are proposed.

Highly Desirable Photodetectors Derived from Versatile Plasmonic Nanostructures

AbstractWith unique ability to concentrate and manipulate light at nanoscale, surface plasmon resonance technologies create additional opportunities for fabricating superintegration photodetectors with desirable functionalities. To gain an insight into the state‐of‐the‐art of plasmonic photodetectors, recent advances in novel devices as well as potential building blocks are presented herein. The article focuses particularly on understanding the enhancement mechanism of different architectures such as nanoparticles, gratings, waveguides, antennas, and microcavities. Meanwhile, challenges and potential design schemes are proposed in this inspiring field.

Superior Plasmonic Photodetectors Based on Au@MoS2 Core-Shell Heterostructures.

Integrating plasmonic materials into semiconductor media provides a promising approach for applications such as photosensing and solar energy conversion. The resulting structures introduce enhanced light-matter interactions, additional charge trap states, and efficient charge-transfer pathways for light-harvesting devices, especially when an intimate interface is built between the plasmonic nanostructure and semiconductor. Herein, we report the development of plasmonic photodetectors using Au@MoS2 heterostructures-an Au nanoparticle core that is encapsulated by a CVD-grown multilayer MoS2 shell, which perfectly realizes the intimate and direct interfacing of Au and MoS2. We explored their favorable applications in different types of photosensing devices. The first involves the development of a large-area interdigitated field-effect phototransistor, which shows a photoresponsivity ∼10 times higher than that of planar MoS2 transistors. The other type of device geometry is a Si-supported Au@MoS2 heterojunction gateless photodiode. We demonstrated its superior photoresponse and recovery ability, with a photoresponsivity as high as 22.3 A/W, which is beyond the most distinguished values of previously reported similar gateless photodetectors. The improvement of photosensing performance can be a combined result of multiple factors, including enhanced light absorption, creation of more trap states, and, possibly, the formation of interfacial charge-transfer transition, benefiting from the intimate connection of Au and MoS2.