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A leaky mode resonance induced dual-band photodetector is fabricated using graphene/silicon nanowire array heterojunctions, which exhibit two peak responsivities at 430 nm and 660 nm.

This review provides an overview of the basic concepts and operation mechanisms of ultraviolet (UV) photodetectors (PDs), the main research status, and future outlooks of II–VI group compound semiconductor-based UVPDs.

A schematic diagram of the device principle of a wavelength sensor consisting of two horizontally stacked MLG/Ge heterojunctions and the wavelength-dependent photocurrent ratio at different thicknesses of PD1.

Two-dimensional layered (2D) materials are currently attracting intensive research interest for high-performance photodetection and other optoelectronic applications. However, the study of device integration for multifunctional optoelectronic applications is still at a nascent stage. Here, the assembly of a multilayered PtSe2/pyramid-Si heterostructure-based photodetector array consisting of 8 × 8 device units is demonstrated. Owing to the pronounced light confinement effect of the heterostructures, the devices present an prominent photovoltaic effect, which enables efficient self-driven photodetection in a broadband wavelength spectrum. The Ilight/Idark ratio, responsivity, external quantum efficiency (EQE) and specific detectivity can attain values as high as 5.51 × 106, 567 mA W−1, 87% and 1.26 × 1013 jones, respectively, upon 810 nm near-infrared (NIR) light illumination. What is more, benefiting from the large-scale homogeneous material growth technique, the photodetector array exhibits excellent uniformity and repeatability in photoresponse performance with negligible unit-to-unit variation. The above characteristics provide the photodetector array with the capability of recording a simple image produced by NIR illumination and monitoring a moving photonic signal, showing the great possibility for NIR image sensing and light trajectory tracking applications.

Multispectral photodetection has garnered enormous research interest and has always been challenging to date. Here, we present the realization of an electrically adjusted single-band/dual-band photodetector based on an inorganic lead-free halide Cs3Cu2I5/two-dimensional (2D) PdTe2 multilayer/Ge multiheterostructure. Owing to its unique optical property and distinct carrier transport behaviour, the device can be easily converted from a single-band photodetector operating in the near-infrared (NIR) region to a dual-band photodetector working in both deep-ultraviolet (DUV) and NIR regimes, upon applying a reverse bias voltage. Significantly, the device shows a peak responsivity of ∼694.1 mA W−1 at 1550 nm at zero bias, and maximum responsivity values of ∼744.2 mA W−1 and ∼712.5 mA W−1 at 265 nm and 1550 nm, respectively, at a small reverse bias. This characteristic also endows the photodetector with an excellent DUV/NIR dual-band optical imaging capability. This work will offer a new opportunity for designing high-performance photodetectors with multiple functionalities operating in complicated circumstances.

GaSe microbelts were successfully synthesized using Ga/Ga2Se3 as the precursor mixture, where excess Ga was required to serve as the metal catalyst. Meanwhile, a spontaneously oxidized surface amorphous oxide (GaOx) layer formed, which induced a built-in electric field perpendicular to the surface. Benefiting from this effect, a GaSe microbelt-based photodetector attained a high responsivity of ∼3866 A W−1 and a photoconductive gain of up to ∼1.06 × 104. This study sheds light on the controlled synthesis of microstructures and provides a device design concept for high-performance micro/nano optoelectronics.

In this work, we present the assembly of a γ-In2Se3/GaAs heterostructure-based photodetector linear array composed of 1 × 10 device units. The layered γ-In2Se3 films with a well-defined pattern are deposited directly onto a planar GaAs substrate via radio-frequency (RF) magnetron sputtering deposition assisted by a pre-photolithography process. The as-fabricated heterojunction exhibits an apparent photovoltaic effect, which endows the device with a function to operate as a self-driven photodetector. The critical photoresponse performance parameters in terms of the Ilight/Idark ratio, responsivity (R), specific detectivity (D*) and response speed can reach 1.29 × 104, 0.25 A W−1, 7.34 × 1012 Jones and 23.6/146.7 μs (rise/fall times), respectively, upon 660 nm light irradiation at 0 V. What is more, further device evaluation reveals that the photodetector array shows good uniformity with a minor unit-to-unit variation. The above merits endow the photodetector array with the ability to monitor a moving optical signal and to record an “E” image produced by visible illumination. It is believed that the present photodetector array is very promising for some optoelectronic purposes such as real-time light trajectory tracking and visible light image sensing applications.

Light detection in the near-infrared (NIR) region is of particular importance due to its wide application for both military and civil purposes. In this study, we fabricated high-performance NIR photodetectors by simply transferring a multilayered PtSe2 film onto a Ge wafer to form vertical hybrid heterojunctions. These heterojunctions exhibit an apparent photovoltaic effect under NIR illumination, offering our devices the opportunity to operate without an external power supply. Based on further optoelectronic analysis, it was found that the devices were highly sensitive to the 1300, 1550, 1650 and even 2200 nm NIR illumination with good reproducibility and long-term air stability. Under the 1550 nm irradiation, the NIR photodetectors attained the high responsivity and specific detectivity of 602 mA W−1 and 6.3 × 1011 Jones, respectively, along with fast response speed of 7.4/16.7 μs at zero bias. Due to the excellent photoresponse performance and the simple device geometry, the present self-driven NIR photodetectors are very promising for application in future optoelectronic devices and systems.

In this study, we report on the synthesis of layered γ-In2Se3 for broadband photodetector and near infrared light image sensing applications. The layered γ-In2Se3 nanofilm with a thickness of around 74 nm was deposited onto a n-Si wafer through radio frequency magnetron sputtering. It is found that the as-assembled γ-In2Se3/n-Si shows an obvious photovoltaic behavior and can work properly as a self-powered broadband photodetector over a wide range of wavelengths (200–2200 nm). Such a unique spectral response beyond the absorption limit of both intrinsic γ-In2Se3 and n-Si can be ascribed to the existence of defect energy levels between the valence band and the conduction band, as a result of Se substitution of In atoms according to theoretical simulation based on first-principles calculations. Specifically, the γ-In2Se3/n-Si photodetector has a responsivity of 0.57 A W−1, a specific detectivity of 2.6 × 1012 Jones and a fast response speed (35/115 μs for τr/τf) under 808 nm light illumination, respectively, which are slightly better or comparable to other devices with similar geometries. Lastly, it was revealed that the γ-In2Se3/n-Si heterojunction photodetector can function as an effective near infrared (NIR) light image sensor with a decent spatial resolution, which suggests the great potential of the current device in future NIR optoelectronic systems.

In this study, a sensitive near-infrared (NIR) photodetector based on a CsBi3I10 perovskite/Si heterojunction is developed by directly coating a layer of inorganic perovskite onto a planar Si substrate. The as-constructed heterojunction displays a representative current rectifying behavior in the dark and remarkable photoresponse properties upon light irradiation. The distinct photovoltaic effect enables the device to function as a self-driven photodetector working at zero bias. Furthermore, it is observed that the photodetector is sensitive in a wide spectral region with peak sensitivity at ∼820 nm. Under 808 nm illumination, the critical photoresponse parameters of responsivity, external quantum efficiency and specific detectivity reached 178.7 mA W−1, 27.2% and 4.99 × 1010 Jones at zero bias, respectively, which can be further increased to as high as 492.1 mA W−1, 75.2% and 1.38 × 1011 Jones at a working bias of −1 V. What is more, the present device also holds a large Ilight/Idark ratio of ∼1 × 104, a rapid response speed of 73/36 μs, and excellent air stability even after 3 months of storage under ambient conditions. Considering the good photoresponse performance and facile assembly approach, the CsBi3I10 perovskite/Si heterojunction possesses huge potential for future cost-effective and high-performance photodetection applications.

A γ-In2Se3/Si heterostructure phototransistor with a broadened photoresponse has been developed, presenting a responsivity, specific detectivity and response speed of 10.24 A W−1, 8.63 × 1012 Jones and 0.76/0.85 ms (rise time/fall time) at 450 nm, respectively. The high responsivity could be attributed to the depressed dark current of the γ-In2Se3 nanofilm and the high gain arising from the gating effect of the phototransistor. Further analysis reveals that the relatively high responsivity and fast response speed facilitate the application of the device in real-time and accurate health monitoring, such as heart rate detection.

In this work, we have developed a wavelength sensor that is capable of distinguishing illumination with wavelengths ranging from ultraviolet (UV) to near infrared (NIR). The as-proposed wavelength sensor is geometrically composed of two parallelly stacking graphene (Gr)/thin Si/Gr heterojunction devices, which are identical in device structures, but can display completely different optical properties in terms of distribution of photo-absorption and photo-generation rates under various light illuminations, according to theoretical simulation. Such a discrepancy in optical properties due to a wavelength dependent absorption coefficient and the relatively thin Si wafer gives rise to completely different photocurrent evolution for varied wavelengths of illumination. The relationship between the photocurrent ratio of devices, the wavelength and intensity of incident light can be numerically described by an equation, through which the wavelength in the range from 265 to 1050 nm can be accurately determined. Notably, the average root-mean-square error of this wavelength sensor is about 2.30 nm, with a relative error as low as ±1.5%, which is much better than other wavelength detectors previously reported. These results suggest that the present wavelength sensor may find potential application for future optoelectronic systems.

Recently, by taking advantage of the synergistic effects of both graphene and ZnO, various photoelectric devices that combine graphene and ZnO have exhibited excellent device performances and attracted increasing research interest. However, although significant achievements have been made, many challenges still exist. In this review paper, we comprehensively summarize the recent advances in the fabrication of various graphene (also including reduced graphene oxide)–ZnO (e.g. ZnO films, nanowires, nanotubes, nanorods etc.) hybrid heterostructures, and their application in a number of optoelectronic devices, including photodiodes, phototransistors, solar cells, light emitting diodes (LEDs), lasers and so on. We start by briefly surveying the recent progress in the fabrication methodologies such as low-temperature and high-temperature methods. And then, we will elaborate on the optoelectronic device application in terms of device physics, performance analysis, and device optimization approaches. Finally, we close with some unresolved issues and challenges in this field.

Plasmonic optoelectronic device based non-noble metal nanostructures (e.g. Al, In, etc.) have recently received increasing research interest due to their relatively low fabrication cost and tunable plasmon wavelength. In this study, we present a new plasmonic red light nano-photodetector by decorating a multi-layer graphene (MLG)–CdSe nanoribbon (CdSeNR) Schottky junction with a highly ordered plasmonic copper nanoparticle (CuNP) array, which exhibited obvious localized surface plasmon resonance in the range of 700–900 nm. Optoelectronic analysis reveals that the device metrics including the switch ratio, the responsivity and the detectivity considerably increased after functionalization with plasmonic CuNPs. Moreover, the response speed was fastened by nearly one order of magnitude. The observed optimization in device performance, according to theoretical simulations based on the finite element method (FEM) and experimental analysis, could be attributed to localized surface plasmon resonance (LSPR) induced hot electron injection. The above results signify that the present plasmonic CuNPs are equally important candidates for boosting the device performance of nano-optoelectronic devices.

Monolayer hexagonal arsenene (hAs), a typical two-dimensional semiconducting material with a wide band gap and high stability, has attracted increasing research interest due to its potential applications in optoelectronics. Using first-principles calculations, we have investigated the electronic and magnetic properties of x-substituted hAs (x = B, C, N, O, Ga, Ge, Se, and monovacancy) and x-adsorbed hAs (x = As). Our results show that the B-, N-, and Ga-substituted hAs have spin-unpolarized semiconducting characters like pristine hAs, and indirect–direct band gap transitions are induced in the B- and N-substituted systems. In contrast, the O-, Se-, and monovacancy-substituted hAs are metallic, and the C- and Ge-substituted hAs show spin-polarized semiconducting characters with band gaps of 1.1 and 1.3 eV for the spin-up channels and 1.0 and 0.7 eV for the spin-down channels, respectively. For the As-adsorbed hAs, the Fermi level crosses the spin-up states, yielding metallic behavior, while the spin-down channel retains semiconducting character. Detailed analysis of electronic structures for the C-substituted, Ge-substituted, and As-adsorbed hAs shows that strong hybridizations between the doping atoms and As atoms lead to energy splitting near the Fermi level and consequently induce magnetic moments. By selective doping, hAs can be transformed from a spin-nonpolarized semiconductor to a spin-polarized semiconductor, to a half-metal, or even to a metal, which indicates that the doped hAs will have promising potential in future electronics, spintronics, and optoelectronics.

A highly sensitive near infrared light (NIR) photodetector was fabricated by coating a thin layer of Cu film onto a vertical n-type SiNW array through a solution based reduction reaction. The as-fabricated core–shell SiNW array/Cu Schottky junction exhibits an obvious rectifying behavior in the dark with a turn-on voltage of ∼0.5 V and a rectification ratio of about 102 at ±1.5 V. In addition, it shows a pronounced photovoltaic performance when illuminated by NIR light with a wavelength of 980 nm. Such photovoltaic characteristics can allow the device to detect NIR illumination without exterior power supply. Further device analysis reveals that the self-powered NIR photodetector is capable of monitoring ultrafast optical signals with a frequency as high as 30 kHz. What is more, the present device also has obvious advantages of high responsivity, detectivity, on/off ratio, and response speed. Further theoretical simulation reveals that the good device performance is associated with excellent optical and electrical properties of core–shell heterojunction geometry.

Tetragonal KCu7S4 nanobelts (NBs) with width of 200–600 nm and length of up to hundreds of micrometers were facially synthesized via a solution-based method. Electrical analysis reveals that the as-fabricated NB exhibits typical p-type semiconducting characteristics with an exceptionally high carrier mobility of ∼870 cm2 V−1 s−1, which may be attributed to the quasi-1D conduction path along the c axis in the structure of KCu7S4. A further study of a device based on the Cu/KCu7S4 NB/Au Schottky junction shows a stable memory behavior with a set voltage of about 0.6 V, a current ON/OFF ratio of about 104, and a retention time >104 s. Such resistive switching characteristics, according to our analysis are due to the interfacial oxide layers that can efficiently trap the electrons by the oxygen vacancies. This study will offer opportunities for the development of high-performance memory devices with new geometries.

In this study, we present a near infrared (NIR) light photodetector based on a topological insulator antimony telluride (Sb2Te3) film, which was grown on sapphire by molecular beam epitaxy (MBE). Electrical analysis reveals that the resistance of the topological insulator decreases with increasing temperature in the temperature range of 8.5–300 K. Further optoelectronic characterization showed that the as-fabricated photodetector exhibits obvious sensitivity to 980 nm light illumination. The responsivity, photoconductive gain and detectivity were estimated to be 21.7 A/W, 27.4 and 1.22 × 1011 Jones, respectively, which are much better than those of other topological insulators based devices. This study suggests that the present NIR photodetector may have potential application in future optoelectronic devices.

In this study, we reported on the construction of p–n junctions based on crystalline Ga-doped CdS–polycrystalline ZnTe nanostructures (NSs) for optoelectronic device application. The coaxial nano-heterojunction was fabricated by a two-step growth method. It is found that the absorption edge of CdS:Ga–ZnTe:Sb core–shell NSs red shifted to about 580 nm, compared with CdS nanowires (520 nm). The as-fabricated core–shell p–n junction exhibited obvious rectification characteristics with a low turn-on voltage of ∼0.25 V. What is more, it showed stable and repeatable photoresponse to 638 nm light illumination, with a responsivity and a detectivity of 1.55 × 103 A W−1 and 8.7 × 1013 cm Hz1/2 W−1, respectively, much higher than other photodetectors with similar device configurations. The generality of this study suggests that the present coaxial CdS:Ga–ZnTe:Sb core–shell nano-heterojunction will have great potential applications in future nano-optoelectronic devices.

We report a simple AlOx passivation approach to optimize the device performance of a bilayer graphene/gallium arsenide (BLG/GaAs) Schottky junction based near infrared photodetector (NIRPD). The as-fabricated NIRPD is highly sensitive to NIR illumination at zero bias voltage, with a detectivity of 2.88 × 1011, which is much higher than that without passivation (7.3 × 109 cm Hz1/2 W−1). The corresponding responsivity is 5 mA W−1. Additionally, the surface passivation can substantially increase both the response rate (rise/fall time τr/τf from 32/48 μs to 320/380 ns), and lift time. It is expected that such a self-driven NIRPD with fast response and high detectivity will have great potential in the future optoelectronic devices.