Schottky Junction Photodetectors Research Articles

Next-Generation Self-Powered Photodetectors using 2D Bismuth Oxide Selenide Crystals.

The concept of self-powered photodetectors has attracted significant attention due to their versatile applications in areas such as intelligent systems and hazardous substance detection. Among these, p-n junction and Schottky junction photodetectors are the most widely studied types; however, their fabrication processes are often complex and costly. To overcome these challenges, we focused on the emerging self-powered, ultrasensitive photodetector platform based on photoelectrochemical (PEC) principles. This platform leverages the unique properties of the emerging material bismuth oxide selenide (Bi2O2Se), which features a wide bandgap (∼2 eV) and a high absorption coefficient. We utilized chemical exfoliation to obtain thin layers of Bi2O2Se, enabling highly efficient photodetection. The device characterization demonstrated impressive performance metrics, including a responsivity of 97.1 μA W-1 and a specific detectivity of 2 × 108 cm Hz 1/2 W-1. The PEC photodetector also exhibits broad-spectrum sensitivity, from blue to infrared wavelengths, and features an ultrafast response time of ∼82 ms and a recovery time of ∼86 ms, highlighting its practical potential. Moreover, these self-powered photodetectors show excellent stability in electrochemical environments, positioning them promising candidates for integration into future high-efficiency devices.

Van der Waals Schottky Junction Photodetector with Ultrahigh Rectifying Ratio and Switchable Photocurrent Generation.

Metal-semiconductor junctions play an important role in the development of electronic and optoelectronic devices. A Schottky junction photodetector based on two-dimensional (2D) materials is promising for self-powered photodetection with fast response speed and large signal-to-noise ratio. However, it usually suffers from an uncontrolled Schottky barrier due to the Fermi level pinning effect arising from the interface states. In this work, all-2D Schottky junctions with near-ideal Fermi level depinning are realized, attributed to the high-quality interface between 2D semimetals and semiconductors. We further demonstrate asymmetric diodes based on multilayer graphene/MoS2/PtSe2 with a current rectification ratio exceeding 105 and an ideality factor of 1.2. Scanning photocurrent mapping shows that the photocurrent generation mechanism in the heterostructure switches from photovoltaic effect to photogating effect at varying drain biases, indicating both energy conversion and optical sensing are realized in a single device. In the photovoltaic mode, the photodetector is self-powered with a response time smaller than 100 μs under the illumination of a 405 nm laser. In the photogating mode, the photodetector exhibits a high responsivity up to 460 A/W originating from a high photogain. Finally, the photodetector is employed for single-pixel imaging, demonstrating its high-contrast photodetection ability. This work provides insight into the development of high-performance self-powered photodetectors based on 2D Schottky junctions.

Improving ZnO ultraviolet Schottky photodetectors by inserting a MoS2 layer

ZnO Schottky junction photodetectors (PDs) has become a research focus due to their wide application, high-performance and low-cost. However, their development has been limited by the low photo-response. Two-dimensional MoS2 exhibit numerous advantages, including a tunable band gap, a strong exciton effect, and broadband absorption. In this work, we incorporate MoS2 into ZnO thin films using a simple spin-coating method to create Schottky ultraviolet (UV) PDs that show a remarkably increased responsivity (by 885%) and a substantially improved photo-current (by one order of magnitude). Furthermore, they exhibit a relatively low noise equivalent power (5.11×10−13 W) and a high normalized detectivity 2.96×1011 Jones. This outstanding performance can be attributed to the enhanced absorption and efficient charge transfer of ZnO film after introduction of MoS2 layer. In this study, an easy method is presented for creating high-performance ZnO Schottky PDs.

Fabricating the Ti-DLC/Au/Si heterostructure films and high-performance NIR photo-detecting

Titanium-doped Diamond-like carbon (Ti-DLC) has been previously used in photodetectors. However, these photodetectors suffer from large dark currents and long response times, limiting their practicality. In this study, we propose a Ti-DLC/Au/Si Schottky junction photodetector. We effectively suppressed the dark current by incorporating a thin layer of gold while enhancing the light current. The results showed the device shows the optimal performance when the gold is at 3 nm and the Ti-DLC thickness is 68 nm, the specific detectivity of the device reaches 1.8 × 1011 Jones and an optical-to-dark ratio exceeding 105 at zero bias voltage, and the response speed is in the range of tens of microseconds, significantly improving its performance. With its ability to suppress dark current, this Schottky junction photodetector holds excellent potential for various applications in the market.

In-situ fabrication of on-chip 1T’-MoTe2/Ge Schottky junction photodetector for self-powered broadband infrared imaging and position sensing

In-situ fabrication of on-chip 1T’-MoTe2/Ge Schottky junction photodetector for self-powered broadband infrared imaging and position sensing

Facile construction of MXene/Ge van der Waals Schottky junction with Al2O3 interfacial layer for high performance photodetection

MXene/bulk semiconductor vdW Schottky junctions are considered to be a hopeful construction strategy for photodetection applications. However, the existence of interfacial states is an obstacle for their actualization. Herein, we developed a kind of Ti3C2Tx/Ge vdW Schottky junction photodetector with Al2O3 interfacial layer through a facile drop of Ti3C2Tx MXene solution on the well-defined Al2O3/Ge substrate. The Al2O3 interfacial layer brings a positive impact on the suppression of dark current and the improvement of light current. Actually, the device shows remarkable photodetection characteristics at 1550 nm with self-powered mode in term of a high responsivity of 665 mA/W, a large specific detectivity of 1.24 × 1013 Jones, a fast response speed of 73.5/81.5 μs. The device also exhibits a broadband response spectrum from 405 to 1550 nm. These fascinating performances and the simple device preparation make the Ti3C2Tx/Al2O3/Ge vdW Schottky junction be promising for the low cost but high performance optoelectronic devices.

Ultrafast self-powered visible blind UV photodetectors based on MgZnO vertical Schottky junction in crossbar geometry

In order to achieve ultrafast response in MgZnO based self-powered Schottky type photodetectors, it is crucial to decrease both the junction capacitance and carrier transit time. To meet these criteria, Au/MgZnO/ITO Schottky junction photodetectors have been realised in crossbar pattern, wherein the thickness of the MgZnO thin film deposited on patterned ITO-glass substrate is ∼ 200 nm and the cross-sectional area of the devices is 0.032 mm2. The semi-transparent 10 nm Au electrode on top of the MgZnO film serves as the Schottky electrode through which light enters the devices. The vertical geometry of the crossbar pattern and the associated small device cross-section results in a low junction capacitance of the devices of ∼ 27 pF at zero bias, which in turn produces very fast visible blind self-powered ultraviolet (UV) photoresponse with both the rise and fall times of ∼ 1.5 μs, that is hitherto unreported for MgZnO based Schottky junction photodetectors. The devices also demonstrate a peak responsivity of ∼ 49 mA/W at ∼ 280 nm with a cut-off wavelength of 336 nm. These Au/MgZnO/ITO Schottky photodetectors in crossbar pattern, with optimized device area, could be useful in applications requiring fast response, such as UV communication and UV imaging.

High‐Performance Self‐Powered Broadband Schottky Junction Photodetector Based on Graphene‐Silicon van der Waals Heterostructure

The development of information sensing technology depends on overcoming the difficulties of high‐performance broadband photodetection by developing novel devices that incorporate new materials and structural innovations. The combination of silicon with two‐dimensional materials has made a breakthrough in the discoveries of high‐speed, highly sensitive, low‐power broadband photodetectors. Graphene (Gra) is an attractive 2D material because of its unique optical, electrical, mechanical, and thermal properties. Over a wide spectral range, the coupling of Gra and Si can exhibit appealing photosensing behavior. Herein, a high‐performance, self‐powered broadband Schottky junction photodetector formed by the van der Waals stacking of Gra over the n‐Si substrate is demonstrated. The device exhibits a remarkable broadband spectral response from the visible (405 nm) range to the infrared region (1,550 nm). The remarkable values of responsivity, detectivity, and external quantum efficiency of 300 mA W−1, 3.37×1011 Jones, and 90% are achieved, respectively, at 532 nm illumination with a fast rise time of 320 μs. The high‐speed, broadband photoresponse and economical manufacturing of this device make it a potential candidate for the optoelectronics market.

Phase-controlled van der Waals growth of wafer-scale 2D MoTe2 layers for integrated high-sensitivity broadband infrared photodetection

Being capable of sensing broadband infrared (IR) light is vitally important for wide-ranging applications from fundamental science to industrial purposes. Two-dimensional (2D) topological semimetals are being extensively explored for broadband IR detection due to their gapless electronic structure and the linear energy dispersion relation. However, the low charge separation efficiency, high noise level, and on-chip integration difficulty of these semimetals significantly hinder their further technological applications. Here, we demonstrate a facile thermal-assisted tellurization route for the van der Waals (vdW) growth of wafer-scale phase-controlled 2D MoTe2 layers. Importantly, the type-II Weyl semimetal 1T′-MoTe2 features a unique orthorhombic lattice structure with a broken inversion symmetry, which ensures efficient carrier transportation and thus reduces the carrier recombination. This characteristic is a key merit for the well-designed 1T′-MoTe2/Si vertical Schottky junction photodetector to achieve excellent performance with an ultrabroadband detection range of up to 10.6 µm and a large room temperature specific detectivity of over 108 Jones in the mid-infrared (MIR) range. Moreover, the large-area synthesis of 2D MoTe2 layers enables the demonstration of high-resolution uncooled MIR imaging capability by using an integrated device array. This work provides a new approach to assembling uncooled IR photodetectors based on 2D materials.

Self-driven near infrared photoelectric detector based on C<sub>14</sub>H<sub>31</sub>O<sub>3</sub>P-Ti<sub>3</sub>C<sub>2</sub>/Au Schottky junction

Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>, as one of new two-dimensional materials MXene, has abundant surface functional groups (—OH, —F, and —O, etc.) and can exhibit semiconductor properties through further surface functionalization. In addition, it has excellent absorption capabilities for both infrared and visible light. Currently, there is limited research on applying the semiconductor properties of Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> to infrared photodetectors. In this study, a self-driven near-infrared photodetector based on a C<sub>14</sub>H<sub>31</sub>O<sub>3</sub>P-Ti<sub>3</sub>C<sub>2</sub>/Au Schottky junction is developed. The modified C<sub>14</sub>H<sub>31</sub>O<sub>3</sub>P-Ti<sub>3</sub>C<sub>2</sub> two-dimensional semiconductor is prepared by a simple solution method, in which the phosphonic acid group reacts with the hydroxyl group on the Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> surface. The C<sub>14</sub>H<sub>31</sub>O<sub>3</sub>P-Ti<sub>3</sub>C<sub>2</sub>/Au photodetector is constructed by using a drop-coating method at room temperature. The observation of an S-shaped curve in the <i>I</i>-<i>V</i> characteristics indicates the formation of a Schottky junction between C<sub>14</sub>H<sub>31</sub>O<sub>3</sub>P-Ti<sub>3</sub>C<sub>2</sub> nanosheets and the Au electrode. The device exhibits good detection performance in the near-infrared band (808–1342 nm), with a maximum responsivity of 0.28 A/W, a detectivity of 4.3×10<sup>7</sup> Jones and an external quantum efficiency (EQE) of 32.75% under 1064 nm infrared light illumination. The <i>I</i><sub>on</sub>/<i>I</i><sub>off</sub> ratio is 10.4, which is about 7.3 times higher than that under 1342 nm light. The response time and the recovery time of the device are 0.9 s and 0.5 s, respectively. After 10 cycles of <i>I</i>-<i>t</i>, the photocurrent does not show any significant decay, indicating excellent repeatability and cycle stability of the device. Owing to the built-in electric field formed by the Schottky junction, photo-generated electrons and holes can quickly separate and produce photocurrent in the external circuit without the need for external voltage driving. In addition, the C<sub>14</sub>H<sub>31</sub>O<sub>3</sub>P-Ti<sub>3</sub>C<sub>2</sub> film obtained by drop-casting on Au is composed of several layers of nanosheets that are randomly stacked, which can effectively relax the plasma momentum limitation, promote the generation of hot electrons, and contribute to the photocurrent. As the C<sub>14</sub>H<sub>31</sub>O<sub>3</sub>P-Ti<sub>3</sub>C<sub>2</sub>/Au Schottky junction photodetector possesses self-driven characteristics and simple fabrication process, it exhibits great potential applications in detecting weak light signals, such as in the fields of astronomy and biomedical science. The successful fabrication of this photodetector provides a new approach for designing and developing MXene-based near-infrared detectors, thus promoting further advancements in this field.

Graphene-silicon-graphene Schottky junction photodetector with field effect structure.

Graphene has unique advantages in ultrabroadband detection. However, nowadays graphene-based photodetectors cannot meet the requirements for practical applications due to their poor performance. Here, we report a graphene-silicon-graphene Schottky junction photodetector assisted by field effect. Two separate graphene sheets are located on both sides of the n-doped silicon to form two opposite lateral series heterojunctions with silicon, and a transparent top gate is designed to modulate the Schottky barrier. Low doping concentration of silicon and negative gate bias can significantly raise the barrier height. Under the combined action of these two measures, the barrier height increases from 0.39 eV to 0.77 eV. Accordingly, the performance of the photodetector has been greatly improved. The photoresponsivity of the optimized device is 2.6 A/W at 792 nm, 1.8 A/W at 1064 nm, and 0.42 A/W at 1550 nm, and the on/off photo-switching ratio reaches 104. Our work provides a feasible solution for the development of graphene-based optoelectronic devices.

Weyl-Semimetal TaIrTe4/Si Nanostructures for Self-Powered Schottky Photodetectors

Weyl semimetal-based photodetectors have attracted great attention due to their high performance in fast, self-powered, and ultra-broad-band photodetection. However, the inherent large dark current of the semimetal hinders further improvement of their performance. Thus, it is urgent to utilize a van der Waals (vdW) heterojunction strategy to effectively decrease the dark current and separate the carriers. Herein, a vertical Schottky junction photodetector based on Weyl semimetal TaIrTe4 and n-Si nanostructures has been studied. The junction presents a high photoresponsivity of 910 mA W–1, a specific detectivity of ∼1.04 × 1011 jones, and a fast response speed of 15.1/18.2 μs under 808 nm irradiation. Furthermore, a stable and reproducible broad-band detection (325–2000 nm) is achieved, due to the efficient NIR light absorption of TaIrTe4. In particular, the device presents impressive responsivities of 14/1.32/0.45 mA W–1 under 1310/1550/2000 nm light, respectively. Notably, these excellent performances of the TaIrTe4/Si nanostructures are superior to those of most of the previously explored 2D materials/Si-based devices and are comparable to those of several commercial silicon photodiode sensors. It is believed that the above results can provide ideas for the research of Weyl semimetals in the application of high-performance nanoscale optoelectronic devices.

High performance broadband self-driven photodetector based on MXene (Ti3C2Tx)/GaAs Schottky junction

As a novel family of 2D materials, MXenes are supposed to play a vital role in optoelectronic devices and systems due to their high conductivity, good optical properties, and favorable compatibility with water and organic solvents. However, the application of MXenes in highly sensitive photodetection is far scarcely investigated. Here, we demonstrate high-quality Ti3C2Tx/GaAs Schottky junction by simply dripping Ti3C2Tx MXene solution on a pre-patterned GaAs substrate. Owing to the wide absorption of MXene and the good quality junction, the self-driven Ti3C2Tx/GaAs Schottky junction photodetector with an impressive performance is realized. The assembled photodetector exhibits a high sensitivity over a wide waveband with a good responsivity of ~1.46 A/W, a large specific detectivity of ~1.23 × 1013 Jones, and a high Ilight/Idark ratio of 5.6 × 105. Significantly, the photodetector is capable of sensing infrared light signal up to 980 nm which exceeds the absorption edge of GaAs (874 nm) due to the generation of hot electrons in Ti3C2Tx MXene film. Given the superior device performance along with a simple and facile fabrication method, the Ti3C2Tx/GaAs Schottky junction photodetector may find the great potential in high performance broadband, self-driven photodetection applications.

Highly sensitive solar-blind deep ultraviolet photodetector based on graphene/PtSe2/β-Ga2O3 2D/3D Schottky junction with ultrafast speed

There is an emerging need for high-sensitivity solar-blind deep ultraviolet (DUV) photodetectors with an ultra-fast response speed. Although nanoscale devices based on Ga2O3 nanostructures have been developed, their practical applications are greatly limited by their slow response speed as well as low specific detectivity. Here, the successful fabrication of two-/three-dimensional (2D/3D) graphene (Gr)/PtSe2/β-Ga2O3 Schottky junction devices for high-sensitivity solar-blind DUV photodetectors is demonstrated. Benefitting from the high-quality 2D/3D Schottky junction, the vertically stacked structure, and the superior-quality transparent graphene electrode for effective carrier collection, the photodetector is highly sensitive to DUV light illumination and achieves a high responsivity of 76.2 mA/W, a large on/off current ratio of ~ 105, along with an ultra-high ultraviolet (UV)/visible rejection ratio of 1.8 × 104. More importantly, it has an ultra-fast response time of 12 µs and a remarkable specific detectivity of ~ 1013 Jones. Finally, an excellent DUV imaging capability has been identified based on the Gr/PtSe2/β-Ga2O3 Schottky junction photodetector, demonstrating its great potential application in DUV imaging systems.

High responsivity of Gr/ n-Si Schottky junction near-infrared photodetector

Si PN junction (p-Si/n-Si) photodetectors have been widely used in the near-infrared band. In this paper, the original p-Si is replaced by graphene to form a Gr/n-Si Schottky junction photodetector. Due to the excellent photoelectric properties of graphene, the incident light can irradiate the depletion region of the Schottky junction to generate more photo-generated carriers and has a higher barrier height, which corresponds to large electric field, and accelerates the photogenerated carriers to the electrodes, resulting in the effective collection of photogeneration of charges. The experimental results show that the Gr/n-Si Schottky junction photodetector has better performance. Under the illumination of 808 nm laser lamp, the I–V characteristic of the device was measured, the dark current of Gr/n-Si Schottky junction photodetector has reduced by two orders of magnitude, while the photocurrent was improved, the barrier height reaches 0.938eV, and the quantum efficiency increases to 71%. Besides, the light responsivity and detectivity are significantly improved to about 0.456A/W and 7.96×1011cmHz1/2W−1 compared with the p-Si/n-Si photodetector.

Van der Waals Epitaxial Growth of Mosaic-Like 2D Platinum Ditelluride Layers for Room-Temperature Mid-Infrared Photodetection up to 10.6 µm.

Mid-infrared (MIR) photodetection, covering diverse molecular vibrational regions and atmospheric transmission windows, is vital to civil and military purposes. Versatile use of MIR photodetectors is commonly dominated by HgCdTe alloys, InSb, and quantum superlattices, which are limited by strict operation demands, high-cost, and environmental toxicity. Despite the rapid advances of black phosphorus (BP)-based MIR photodetectors, these are subject to poor stability and large-area integration difficulty. Here, the van der Waals (vdW) epitaxial growth of a wafer-scale 2D platinum ditelluride (PtTe2 ) layer is reported via a simple tellurium-vapor transformation approach. The 2D PtTe2 layer possesses a unique mosaic-like crystal structure consisting of single-crystal domains with highly preferential [001] orientation along the normal direction, reducing the influence of interface defects and ensuring efficient out-of-plane carrier transportation. This characteristic, combined with the wide absorption of PtTe2 and well-designed vertical device architecture, makes the PtTe2 /Si Schottky junction photodetector capable of sensing ultra-broadband light of up to 10.6 µm with a high specific detectivity. Also, the photodetector exhibits an excellent room-temperature infrared-imaging capability. This approach provides a new design concept for high-performance, room-temperature MIR photodetection based on 2D layered materials.

Improvement of Photoresponse Properties of Self-Powered ITO/InP Schottky Junction Photodetector by Interfacial ZnO Passivation

A self-powered ITO/ZnO/InP heterojunction photodetector has been demonstrated with a 10-nm ZnO interfacial layer deposited by atomic layer deposition as a hole-blocking layer. The presence of a valence band offset between InP and ZnO enhances the photocurrent. The valence band offset between InP and ZnO creates a sufficient barrier for hole movement. Low surface recombination under 520-nm laser irradiation produced maximum photoresponsivity of 44.2 mAW−1 with an illumination power of 1 µW at zero bias. The ZnO-passivated self-powered photodetector shows fast response and improved photo-detecting properties. Furthermore, the highly sensitive photodetectors are demonstrated to record the heart pulse wave by measuring relative changes in blood volume of the finger vessels.

Role of nanowire length on the performance of a self-driven NIR photodetector based on mono/bi-layer graphene (camphor)/Si-nanowire Schottky junction

In this article, we have demonstrated a solid carbon source such as camphor as a natural precursor to synthesize a large area mono/bi-layer graphene (MLG) sheet to fabricate a nanowire junction-based near infrared photodetectors (NIRPDs). In order to increase the surface-to-volume ratio, we have developed Si-nanowire arrays (SiNWAs) of varying lengths by etching planar Si. Then, the camphor-based MLG/Si and MLG/SiNWAs Schottky junction photodetectors have been fabricated to achieve an efficient response with self-driven properties in the near infrared (NIR) regime. Due to a balance between light absorption capability and surface recombination centers, devices having SiNWAs obtained by etching for 30 min shows a better photoresponse, sensitivity and detectivity. Fabricated NIRPDs can also be functioned as self-driven devices which are highly responsive and very stable at low optical power signals up to 2 V with a fast rise and decay time of 34/13 ms. A tremendous enhancement has been witnessed from 36 μA W−1 to 22 mA W−1 in the responsivity at 0 V for MLG/30 min SiNWAs than planar MLG/Si PDs indicating an important development of self-driven NIRPDs based on camphor-based MLG for future optoelectronic devices.

Probing bias and power dependency of high-performance broadband Mg/ZnSnP2/Sn back-to-back Schottky junction photodetectors

Two non-identical Mg/ZnSnP2 and ZnSnP2/Sn Schottky diodes connected in coplanar back-to-back configuration are fabricated on p-type silicon (100) substrate for photodetection in the UV-VIS-NIR spectral region. A detailed study of the power and bias dependent responsivity, detectivity, and response and recovery speed of the devices is reported. The responsivity and detectivity were found to be 0.2 A W-1 and 4.62 × 1012 Jones for the Mg/ZnSnP2 and 0.03 A W-1 and 1.62 × 1011 Jones for the Sn/ZnSnP2 junctions, respectively when they were operated without bias. However, under a reverse bias of 2.5 V, these values changed to 4.7 A W-1 and 1.19 × 1012 Jones in the case of Mg/ZnSnP2 and 12.7 A W-1 and 4.78 × 1011 Jones for Sn/ZnSnP2 junctions, respectively. The photocurrents associated with both the junctions were increased superlinearly with illumination power which is correlated to the conversion of the existing traps within the forbidden energy gap to the recombination centers. The response and recovery speed of the photodetectors were also studied under variable bias and illumination power. Under an incident power of 0.34 mW, the rise and decay times for the Mg/ZnSnP2 and Sn/ZnSnP2 junctions were 200 μs, 2300 μs and 390 μs, 240 μs, respectively at 2.5 V. The Mg/ZnSnP2 showed an anomalous bias dependent secondary decay channel which disappeared at self-powered configuration. The frequency-dependent capacitance in the dark and illumination power-dependent capacitance of the structure were also performed to understand the presence of defect states and the capture of photogenerated carriers by the traps and recombination centers.

Self-driven all-inorganic perovskite microplatelet vertical Schottky junction photodetectors with a tunable spectral response

An all-inorganic perovskite self-driven vertical Schottky junction photodetector with a tunable spectral response is reported.