Range Of Photodetectors Research Articles

High‐Performance Broadband Photodetectors of Heterogeneous 2D Inorganic Molecular Sb2O3/Monolayer MoS2 Crystals Grown via Chemical Vapor Deposition

AbstractThe newly emerged 2D materials heterostructures, including layered and nonlayered structures, are regarded as the building blocks for future high performance optoelectronic devices. However, it still remains a great challenge to directly synthesize 2D heterostructures for realizing broadband detection in photodetectors. In this work, the growth of vertically stacked inorganic molecular Sb2O3/monolayer MoS2 heterostructures through a two‐step chemical vapor deposition method is demonstrated, and high performance ultraviolet/near‐infrared photodetectors based on the achieved heterostructures are further developed. Excellent responsivity of 5.3 × 104 A W−1 and detectivity of 2.0 × 1015 Jones are obtained under 457 nm illumination. Additionally, the photodetection range can be extended to near‐infrared region. Maximum responsivity of 7.8 A W−1, detectivity of 3.4 × 1011 Jones, and fast response speed (<60 ms) are obtained under 1064 nm laser illumination at room temperature, which is far superior to those of the previously reported ultra‐thin 2D van de Waals heterostructures. The inorganic molecular Sb2O3/monolayer MoS2 heterostructures enrich the family of 2D materials heterostructures, showing potential applications in high performance functional electronics and optoelectronics.

Bandgap engineering in CuO nanostructures: Dual-band, broadband, and UV-C photodetectors

In this work, the bandgap of CuO (p-type semiconductor) has been engineered from an indirect bandgap of ∼1 eV to a direct bandgap of 4 eV just by tuning the nanostructure morphology and midgap defect states. The absorption in near-infrared (NIR) and visible regions is ordinarily suppressed by controlling the growth parameters. Considering the increasing scope and demand of varying spectral range (UV-C to NIR) photodetectors, the systematic variation of the available density of states (DOS) at a particular energy level in CuO nanostructures has been utilized to fabricate dual-band (250 nm and 900 nm), broadband (250 nm–900 nm), and UV-C (250 nm) photodetectors. The sensitivity and detectivity of the photodetector for broadband detectors were ∼103 and 2.24 × 1011 Jones for the wavelengths of 900 nm and 122 and 2.74 × 1010 Jones for 250 nm wavelength light, respectively. The UV-C detector showed a sensitivity of 1.8 and a detectivity of 4 × 109 Jones for 250 nm wavelength light. A plausible mechanism for the photoconduction has been proposed for explaining the device operation and the effect of variation in available DOS. The obtained photodetectors are the potential candidates for future optoelectronic applications.

GeSn resonant-cavity-enhanced photodetectors for efficient photodetection at the 2 µm wavelength band.

The 2 µm wavelength band has recently gained increased attention for potential applications in next-generation optical communication. However, it is still challenging to achieve effective photodetection in the 2 µm wavelength band using group-IV-based semiconductors. Here we present an investigation of GeSn resonant-cavity-enhanced photodetectors (RCEPDs) on silicon-on-insulator substrates for efficient photodetection in the 2 µm wavelength band. Narrow-bandgap GeSn alloys are used as the active layer to extend the photodetection range to cover the 2 µm wavelength band, and the optical responsivity is significantly enhanced by the resonant cavity effect as compared to a reference GeSn photodetector. Temperature-dependent experiments demonstrate that the GeSn RCEPDs can have a wider photodetection range and higher responsivity in the 2 µm wavelength band at higher temperatures because of the bandgap shrinkage. These results suggest that our GeSn RCEPDs are promising for complementary metal-oxide-semiconductor-compatible, efficient, uncooled optical receivers in the 2 µm wavelength band for a wide range of applications.

Silicon-based high-responsivity GeSn short-wave infrared heterojunction phototransistors with a floating base.

We demonstrate silicon-based $p \text{-} n \text{-} p$p-n-p floating-base GeSn heterojunction phototransistors with enhanced optical responsivity for efficient short-wave infrared (SWIR) photodetection. The narrow-bandgap GeSn active layer sandwiched between the $p \text{-} {\rm Ge}$p-Ge collector and $n \text{-} {\rm Ge}$n-Ge base effectively extends the photodetection range in the SWIR range, and the internal gain amplifies the optical response by a factor of more than three at a low driving voltage of 0.4 V compared to that of a reference GeSn $p \text{-} i \text{-} n$p-i-n photodetector (PD). We anticipate that our findings will be leveraged to realize complementary metal-oxide-semiconductor-compatible, sensitive, low driving voltage SWIR PDs in a wide range of applications.

Ultrafast Photodetector by Integrating Perovskite Directly on Silicon Wafer.

Single-crystal (SC) perovskite is currently a promising material due to its high quantum efficiency and long diffusion length. However, the reported perovskite photodetection range (<800 nm) and response time (>10 μs) are still limited. Here, to promote the development of perovskite-integrated optoelectronic devices, this work demonstrates wider photodetection range and shorter response time perovskite photodetector by integrating the SC CH3NH3PbBr3 (MAPbBr3) perovskite on silicon (Si). The Si/MAPbBr3 heterojunction photodetector with an improved interface exhibits high-speed, broad-spectrum, and long-term stability performances. To the best of our knowledge, the measured detectable spectrum (405-1064 nm) largely expands the widest response range reported in previous perovskite-based photodetectors. In addition, the rise time is as fast as 520 ns, which is comparable to that of commercial germanium photodetectors. Moreover, the Si/MAPbBr3 device can maintain excellent photocurrent performance for up to 3 months. Furthermore, typical gray scale face imaging is realized by scanning the Si/MAPbBr3 single-pixel photodetector. This work using an ultrafast photodetector by directly integrating perovskite on Si can promote advances in next-generation integrated optoelectronic technology.

Porous Si-SiO2 UV Microcavities to Modulate the Responsivity of a Broadband Photodetector.

Porous Si-SiO2 UV microcavities are used to modulate a broad responsivity photodetector (GVGR-T10GD) with a detection range from 300 to 510 nm. The UV microcavity filters modified the responsivity at short wavelengths, while in the visible range the filters only attenuated the responsivity. All microcavities had a localized mode close to 360 nm in the UV-A range, and this meant that porous Si-SiO2 filters cut off the photodetection range of the photodetector from 300 to 350 nm, where microcavities showed low transmission. In the short-wavelength range, the photons were absorbed and did not contribute to the photocurrent. Therefore, the density of recombination centers was very high, and the photodetector sensitivity with a filter was lower than the photodetector without a filter. The maximum transmission measured at the localized mode (between 356 and 364 nm) was dominant in the UV-A range and enabled the flow of high energy photons. Moreover, the filters favored light transmission with a wavelength from 390 nm to 510 nm, where photons contributed to the photocurrent. Our filters made the photodetector more selective inside the specific UV range of wavelengths. This was a novel result to the best of our knowledge.

Tunable electronic properties of multilayer InSe by alloy engineering for high performance self-powered photodetector

Multilayer indium selenide (InSe) is a good candidate for high performance electronic and optoelectronic devices. The electrical performance of InSe is effectively regulated by dielectric layers, contact electrodes and surface doping. However, as a powerful tool to tune properties of materials, alloy engineering is absent for multilayer InSe. In this letter, for the first time, we investigate the electrical property of InSe1-xTex alloys and optoelectronic property of InSe-InSe0.82Te0.18p-n heterojunction. The electrical transport properties of InSe1-xTex alloys strongly depend on the content of Te composition. With the ratio of Te/Se increasing, the n-type electron transport behavior of InSe gradually transfers to the p-type hole transport behavior of InSe0.82Te0.18. The p-n InSe-InSe0.82Te0.18 heterojunction shows a rectification effect and a self-powered photodetection. The self-powered photodetector (SPPD) has a broad photodetection range from visible light (400 nm) to near-infrared (NIR) light (1000 nm). The responsivity (R) of SPPD is 14.1 mA/W under illuminated by NIR light (900 nm) at zero bias, which is comparable to some of the 2D heterojunctions NIR photodetectors measured with an external bias. The SPPD also shows a stable and fast response to NIR light (900 nm). This work demonstrates that the electrical transport properties of InSe1-xTex alloys significantly rely on the ratio of Te/Se and suggests that InSe-InSe1-xTex p-n heterojunction has a excellent potential for application in the self-powered optoelectronic device.

Photoelectrical properties of graphene/doped GeSn vertical heterostructures.

GeSn is a group IV alloy material with a narrow bandgap, making it favorable for applications in sensing and imaging. However, strong surface carrier recombination is a limiting factor. To overcome this, we investigate the broadband photoelectrical properties of graphene integrated with doped GeSn, from the visible to the near infrared. It is found that photo-generated carriers can be separated and transported with a higher efficiency by the introduction of the graphene layer. Considering two contrasting arrangements of graphene on p-type and n-type GeSn films, photocurrents were suppressed in graphene/p-type GeSn heterostructures but enhanced in graphene/n-type GeSn heterostructures when compared with control samples without graphene. Moreover, the enhancement (suppression) factor increases with excitation wavelength but decreases with laser power. An enhancement factor of 4 is achieved for an excitation wavelength of 1064 nm. Compared with previous studies, it is found that our graphene/n-type GeSn based photodetectors provide a much wider photodetection range, from 532 nm to 1832 nm, and maintain comparable responsivity. Our experimental findings highlight the importance of the induced bending profile on the charge separation and provides a way to design high performance broadband photodetectors.

Enhanced UV–visible detection of InGaZnO phototransistors via CsPbBr3 quantum dots

Indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) exhibit high field-effect carrier mobility and low off-state current, which are attractive for high speed and low noise photodetectors and image sensor applications. However, with an optical band gap of ∼3.3 eV, the photodetection range of IGZO TFTs is limited to short wavelength ultraviolet (UV) light. Here, we demonstrate a simple approach to enhance the performance of IGZO-based phototransistors by incorporating layers of solution-processed perovskite quantum dots (QDs) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM). Owing to the fast transfer of photogenerated electrons by CsPbBr3 QDs absorbing layer, the photoresponse of QD-decorated IGZO phototransistor is extended to the visible range (500 nm), and the responsivity and detectivity of QD-decorated device are more than two order higher than those of original IGZO TFTs. Moreover, the QD-decorated IGZO phototransistor also exhibits enhanced performance under UV light (350 nm), achieving a responsivity of 9.72 A W−1, a detectivity of 2.96 × 1012 Jones, and a light to dark current ratio in the order of 106 at a wavelength of 350 nm (a light intensity of 207.3 μW cm−2).

Infrared Detectable MoS2 Phototransistor and Its Application to Artificial Multilevel Optic-Neural Synapse.

Layered two-dimensional (2D) materials have entered the spotlight as promising channel materials for future optoelectronic devices owing to their excellent electrical and optoelectronic properties. However, their limited photodetection range caused by their wide bandgap remains a principal challenge in 2D layered materials-based phototransistors. Here, we developed a germanium (Ge)-gated MoS2 phototransistor that can detect light in the region from visible to infrared (λ = 520-1550 nm) using a detection mechanism based on band bending modulation. In addition, the Ge-gated MoS2 phototransistor is proposed as a multilevel optic-neural synaptic device, which performs both optical-sensing and synaptic functions on one device and is operated in different current ranges according to the light conditions: dark, visible, and infrared. This study is expected to contribute to the development of 2D material-based phototransistors and synaptic devices in next-generation optoelectronics.

High-Performance, Room Temperature, Ultra-Broadband Photodetectors Based on Air-Stable PdSe2.

Photodetection over a broad spectral range is crucial for optoelectronic applications such as sensing, imaging, and communication. Herein, a high-performance ultra-broadband photodetector based on PdSe2 with unique pentagonal atomic structure is reported. The photodetector responds from visible to mid-infrared range (up to ≈4.05 µm), and operates stably in ambient and at room temperature. It promises improved applications compared to conventional mid-infrared photodetectors. The highest responsivity and external quantum efficiency achieved are 708 A W-1 and 82 700%, respectively, at the wavelength of 1064 nm. Efficient optical absorption beyond 8 µm is observed, indicating that the photodetection range can extend to longer than 4.05 µm. Owing to the low crystalline symmetry of layered PdSe2 , anisotropic properties of the photodetectors are observed. This emerging material shows potential for future infrared optoelectronics and novel devices in which anisotropic properties are desirable.

Effect of Stone-Wales defect on an armchair graphene nanoribbon-based photodetector

Abstract The effect of Stone-Wales (SW) defect on the performance of an armchair graphene nanoribbon (AGNR)-based photodetector is studied. To model the SW defect two new tight-binding (TB) parameters are proposed that provide results that are in good agreement with density functional theory calculations. SW defect is introduced in different locations in the channel of the AGNR detector and the photocurrent, quantum efficiency and responsivity of defected structures are calculated using TB approximation and non-equilibrium Green's function formalism. By inspecting the photo-generated hole density in different points of the channel, the way that photocurrent is affected by SW defect in different defected structures is investigated. Our results show that the photocurrent of AGNR photodetector varies with the number and position of SW defect in the channel. Among the defected structures highest quantum efficiency is observed in the structure in which the SW defect is located near the contact with a higher bias voltage. However, the quantum efficiency in all defected structures is lower than their perfect counterpart. Since the low ratio of the photocurrent to the dark current limits the performance of photodetectors, improving this ratio is of great importance. We show that the presence of SW defect in the channel of AGNR photodetector increases this ratio. It is observed that the ratio of photocurrent to the dark current in the double-defect structure in which two SW defects are located at two ends of the channel is 4.7 times larger than the perfect photodetector. Our results also show that by inserting SW defect in the channel of AGNR photodetector its photo-detection range can be tuned to higher energies.

Photodetection by Hot Electrons or Hot Holes: A Comparable Study on Physics and Performances.

Hot-carrier photodetectors are drawing significant attention; nevertheless, current researches focus mostly on the hot-electron devices, which normally show low quantum efficiencies. In contrast, hot-hole photodetectors usually have lower barriers and can provide a wide spectral range of photodetection and an improved photoconversion efficiency. Here, we report a comparable study of the hot-electron and hot-hole photodetectors from both underlying physics and optoelectronic performance perspectives. Taking the typical Au/Si Schottky contact as an example, we find obvious differences in the energy band diagram and the sequent hot-carrier generation/transport/emission processes, leading to very distinguished photodetection performances. Compared with hot electrons, hot holes show higher density below the Fermi level, the longer mean free path arising under the lower electron–electron and electron–phonon scatterings, a lower barrier height, and a lighter effective mass in Si, all of which lead to larger number of high-energy hot holes, larger transport probability, higher emission efficiency, and higher photoresponsivity. However, the low barrier height can cause poor performances of hot-hole device in dark current density and detectivity. The study elucidates the intrinsic physical differences and compares the key performance parameters of the hot-hole and hot-electron photodetections, with the objective of providing complete information for designing hot-carrier devices.

Noise analysis of optimized $${\text{Ge}}/{\text{Ge}}_{{1 - {\text{x}}}} {\text{Sn}}_{\text{x}} /{\text{Ge}}$$ Ge / Ge 1 - x Sn x / Ge p–n–p heterojunction phototransistors for long-wavelength optical receivers

Present literature investigates noise analysis and optimal design for \({\text{Ge}}/{\text{Ge}}_{1 - {\text{x}}} {\text{Sn}}_{\text{x}} /{\text{Ge}}\) based p–n–p heterojunction phototransistors (HPT) for long-wavelength optical receivers. We calculate gain, noise powers, signal-to-noise ratio, absorption coefficient and optical responsivity of proposed GeSn-based HPT and investigate their dependence on various structural parameters to optimize the design. The proposed HPT incorporates \({\text{Ge}}_{{1 - {\text{x}}}} {\text{Sn}}_{\text{x}}\) alloy in the base layer as the active layer, allow to extend the photo detection range from near infrared to mid-infrared to achieve a wide range of detection. The results show that the signal-to-noise ratio (SNR) is strongly dependent on the operating frequency and the introduction of Sn in the base layer can improve the signal-to-noise ratio in the high-frequency region. The calculated results also show that even in the presence of small defects and misfit dislocations at the heterointerfaces, high SNR is still achievable for the proposed structure.

Comprehensive Analysis and Optimal Design of Ge/GeSn/Ge p-n-p Infrared Heterojunction Phototransistors

We present a comprehensive analysis of practical p-n-p Ge/Ge1– x Sn x /Ge heterojunction phototransistors (HPTs) for design optimization for efficient infrared detection. Our design includes a Ge1– x Sn x narrow-bandgap semiconductor as the active layer in the base layer, enabling extension of the photodetection range from near-infrared to mid-infrared to perform wide-range infrared detection. We calculate the current gain, signal-to-noise ratio (SNR), and optical responsivity and investigate their dependences on the structural parameters to optimize the proposed Ge1– x Sn x p-n-p HPTs. The results show that the SNR is strongly dependent on the operation frequency and that the introduction of Sn into the base layer can improve the SNR in the high-frequency region. In addition, the current gain strongly depends on the Sn content in the Ge1– x Sn x base layer, and a Sn content of 6%–9% maximizes the optical responsivity achievable in the infrared range. These results provide useful guidelines for designing and optimizing practical p-n-p Ge1– x Sn x HPTs for high-performance infrared photodetection.

UV-SWIR broad range photodetectors made from few-layer α-In2Se3 nanosheets.

Photodetectors are very important for many applications. However, inexpensive infrared photodetectors with high performance at room temperature are still rare. Furthermore, it is still a great challenge to realize on-chip wide-spectrum detection by using conventional photodetectors. van der Waals semiconductors are promising for high performance optoelectronic devices. Here, we report broad range photodetectors made from few-layer α-In2Se3 nanosheets. The photodetectors show response in an unexpected broad range from ultraviolet (325 nm) to short-wavelength infrared (1800 nm) at room temperature. The optical response in the long wavelengths beyond the bandgap is attributed to oxygen absorption and oxygen-associated selenium defects in In2Se3, supported by theoretical simulation and controlled experiments. High responses to 700 nm and 1550 nm lasers are demonstrated on the same In2Se3 device. The stability of In2Se3 under the atmosphere at room temperature and the low power consumption of the devices make the In2Se3 photodetectors promising for optoelectronic applications.

Optimized Ge1−&lt;italic&gt;x&lt;/italic&gt;Sn&lt;italic&gt;x&lt;/italic&gt;/Ge Multiple-Quantum-Well Heterojunction Phototransistors for High-Performance SWIR Photodetection

We present the design and analysis of three-terminal Ge1− x Sn x /Ge multiple-quantum-well (MQW) heterojunction phototransistors (HPTs) for high-performance short-wave infrared (SWIR) photodetection. The active layer incorporates Ge1− x Sn x /Ge MQW structures between base–collector junctions pseudomorphically grown on Ge-on-Si substrates, thereby providing compatibility with CMOS platforms for low cost and scalable manufacturing technology. Introducing Sn into the MQW structures can effectively reduce the direct bandgap, thereby considerably extending the photodetection range in the SWIR spectral range with improved absorption efficiencies. In addition, the use of MQW structures as the active layer can enhance the absorption coefficient via quantum-confinement effects, thus further enhancing the photoresponses. We develop theoretical models to calculate the strained electronic band structures and optical absorption coefficients for the Ge1− x Sn x /Ge MQW structures, and the current gain is evaluated as a function of the barrier/well thicknesses, number of periods of the MQW structures, and doping concentrations of the layers for the HPT structures. The calculation results show that the absorption coefficient can be significantly enhanced by increasing the Sn content in the Ge1− x Sn x /Ge MQW active layer, and the current gain can be considerably enhanced by optimizing the HPT structures. With the enhanced absorption coefficient and current gain, high-responsivity photodetection can be achieved in the SWIR spectral range, thus making this device very promising for a wide range of SWIR photodetection applications.

GeSn resonant-cavity-enhanced photodetectors on silicon-on-insulator platforms

We report GeSn p-i-n resonant-cavity-enhanced photodetectors (RCEPDs) grown on silicon-on-insulator substrates. A vertical cavity, composed of a buried oxide as the bottom reflector and a deposited SiO2 layer on the top surface as the top reflector, is created for the GeSn p-i-n structure to enhance the light-matter interaction. The responsivity experiments demonstrate that the photodetection range is extended to 1820nm, completely covering all the telecommunication bands, because of the introduction of 2.5% Sn in the photon-absorbing layer. In addition, the responsivity is significantly enhanced by the resonant cavity effects, and a responsivity of 0.376A/W in the telecommunication C-band is achieved that is significantly higher than that of conventional GeSn-based PDs. These results demonstrate the feasibility of CMOS-compatible, high-responsivity GeSn-based PDs for shortwave infrared applications.

Fabrication of Bi19S27I3 nanorod cluster films for enhanced photodetection performance.

Thin-film photodetectors built from one-dimensional nanostructures have attracted extensive attention due to their significance in basic scientific research and potential technological applications. It is still desirable to develop new materials with a wide response range for application in photodetectors. In this work, a Bi19S27I3 nanorod cluster film has been successfully fabricated on various rigid substrates by a facile solvothermal method. The component nanorods exhibit an oriented growth along the [001] direction. The UV-Vis-NIR absorption spectrum shows a continuous strong absorption spanning the whole visible light to near-infrared region and presents a direct band gap of 0.83 eV for the prepared Bi19S27I3 nanorod clusters. The spectral photoresponse of the Bi19S27I3-based photodetector device demonstrates a broad photoresponse ranging from ultraviolet to near infrared. The photocurrent results reveal that the photodetector exhibits a more sensitive response towards near-infrared light than visible light. Furthermore, the photodetector based on the Bi19S27I3 nanorod cluster film shows significantly enhanced photodetection performance compared to Bi19S27I3 nanorod powder. The photocurrent and on-off ratio of the prepared nanorod cluster film are respectively up to 400 times and several times higher than those of the powder sample. The on-off ratios are about 265 and 66 under NIR illumination and 48 and 11 under visible light for the film and powder samples, respectively. These results suggest a great potential application of the prepared Bi19S27I3 nanorod cluster film in optoelectronic devices.

Electronic properties and potential applications of the heterojunction between silicon and multi‐nanolayer amorphous selenium

The electronic properties of the junction formed between multi-nanolayer amorphous selenium and silicon are studied. The current–voltage (I–V) relationship of this type of junction was characterised and the result showed pn junction rectification. Capacitance–voltage (C–V) measurements were also used to obtain the value of the diffusion potential of the junction. From these data, the ideality factor and built-in potential were evaluated. The results show potential in the application of amorphous selenium and silicon as materials in tandem photovoltaic cells and in wide spectral range photodetectors.