Efficient Assembly of Bridged β‐Ga2O3 Nanowires for Solar‐Blind Photodetection

An increasing number of applications using ultraviolet radiation have renewed interest in ultraviolet photodetector research. Particularly, solar‐blind photodetectors sensitive to only deep UV (<280 nm), have attracted growing attention because of their wide applicability. Among recent advances in UV detection, nanowire (NW)‐based photodetectors seem promising, however, none of the reported devices possesses the required attributes for practical solar‐blind photodetection, namely, an efficient fabrication process, a high solar light rejection ratio, a low photocurrent noise, and a fast response. Herein, the assembly of β‐Ga₂O₃ NWs into high‐performance solar‐blind photodetectors by use of an efficient bridging method is reported. The device is made in a single‐step chemical vapor deposition process and has a high 250‐to‐280‐nm rejection ratio (～2 × 10³), low photocurrent fluctuation (<3%), and a fast decay time (<<20 ms). Further, variations in the synthesis parameters of the NWs induce drastic changes in the photoresponse properties, which suggest a possibility for tuning the performance of the photodetectors. The efficient fabrication method and high performance of the bridged β‐Ga₂O₃ NW photodetectors make them highly suitable for solar‐blind photodetection.     

A high efficient 820 nm MOS Ge quantum dot photodetector

A Ge quantum dot photodetector has been demonstrated using a metal-oxide-semiconductor (MOS) tunneling structure. The oxide film was grown by liquid phase deposition (LPD) at 50/spl deg/C. The photodetector with five-period Ge quantum dot has responsivity of 130, 0.16, and 0.08 mA/W at wavelengths of 820 nm, 1300 nm, and 1550 nm, respectively. The device with 20-period Ge quantum dot shows responsivity of 600 mA/W at the wavelength of 850 nm. The room temperature dark current density is as low as 0.06 mA/cm/sup 2/. The high performance of the photodetectors at 820 nm makes it feasible to integrate electrooptical devices into Si chips for short-range optical communication.     

PbS量子点同质P-N结光电探测器

PbS胶体量子点因其带隙可调、可溶液加工、吸收系数高等优异特性而广泛应用于光电探测器领域。然而基于光电二极管结构的PbS量子点光电探测器通常会使用不同的材料来制备N型层,从而增加了器件设计和工艺的复杂性,不利于这类光电探测器未来在面阵成像芯片中的应用。为简化制备工艺,提出了一种PbS量子点同质P-N结光电探测器,仅通过一种工艺过程实现了器件P型层和N型层的制备。经测试,探测器对不同入射光强度的探测表现出了良好的线性响应;在0.5 V反向偏压作用下,器件在700 nm处的响应度为0.11 A/W,比探测率为3.41×1011 Jones,展现出了其对弱光探测的优异能力。结果表明文中提出的PbS量子点同质PN结光电探测器有助于推动其在面阵成像领域中的发展。     

Optical properties of photodetectors based on single GaN nanowires with a transparent graphene contact

We report the fabrication and optical and electrical characterization of photodetectors for the UV spectral range based on single p–n junction nanowires with a transparent contact of a new type. The contact is based on CVD-grown (chemical-vapor deposition) graphene. The active region of the nitride nanowires contains a set of 30 radial In_0.18Ga_0.82N/GaN quantum wells. The structure is grown by metal-organic vaporphase epitaxy. The photodetectors are fabricated using electron-beam lithography. The current–voltage characteristics exhibit a rectifying behavior. The spectral sensitivity of the photodetector is recorded starting from 3 eV and extending far in the UV range. The maximal photoresponse is observed at a wavelength of 367 nm (sensitivity 1.9 mA/W). The response switching time of the photodetector is less than 0.1 s.     

高功率共振腔增强型光电探测器研究进展

共振腔增强型光电探测器(RCE-PD)作为一种新型光电探测器,具有高量子效率、高响应度和波长选择性等优点,成为目前光纤通信领域中最为重要的探测器之一.在数字和模拟光传输系统中,高功率探测器由于具有高信噪比、低插入损耗等优点,在国际上越来越受到重视.综述了这两种探测器的基本结构、发展状况,展望了其发展前景等.指出高功率共振腔增强型光电探测器将是今后最有发展前途的探测器.     

光电探测器结构对光响应特性的影响

为了研究不同结构光电探测器的光响应特性,采用脉冲激光沉积技术在玻璃衬底上制备了ZnO基紫外探测器。X射线衍射谱、扫描电子显微镜和光致发光光谱显示,ZnO膜为多晶结构,表面平整,并具有良好的化学配比。比较平面结构探测器和夹层式探测器的光响应特性可知,探测器结构对光电探测特性具有重要影响。结果表明,平面结构探测器中的电极宽度引起响应时间和响应度之间的竞争,而具有透明电极氧化铟锡的夹层式探测器则不存在这一问题。     

Broadband Photoresponse Enhancement of a High‐Performance t‐Se Microtube Photodetector by Plasmonic Metallic Nanoparticles

Broadband responsivity enhancement of single Se microtube (Se‐MT) photodetectors in the UV–visible region is presented in this research. The pristine Se‐MT photodetector demonstrates broadband photoresponse from 300 to 700 nm with peak responsivity of ≈19 mA W^?1 at 610 nm and fast speed (rise time 0.32 ms and fall time 23.02 ms). To further enhance the responsivity of the single Se‐MT photodetector, Au and Pt nanoparticles (NPs) are sputtered on these devices. In contrast to only enhancement of responsivity in UV region by Pt NPs, broadband responsivity enhancement (≈600% to ≈800%) of the Se‐MT photodetector is realized from 300 to 700 nm by tuning the size and density of Au NPs. The broadband responsivity enhancement phenomena are interpreted by both the surface modification and surface plasmon coupling. The experimental results of this work provide an additional opportunity for fabricating high‐performance UV–visible broadband photodetectors.     

3D Solar‐Blind Ga2O3 Photodetector Array Realized Via Origami Method

A 3D solar‐blind photodetector array is realized from amorphous Ga₂O₃ films grown on polyethylene terephthalate substrates via an origami route. The photodetector cells exhibit a dark current of 0.17 nA, and the peak responsivity is about 8.9 A W^?1 at 250 nm with a quantum efficiency of 4450%. The photodetector shows a distinct cut‐off wavelength at 268 nm with a solar‐blind ratio of more than two orders of magnitude (photocurrent ratio between 250 nm/300 nm). The photodetector cells reveal excellent electrical stability after thousands of bending cycles. All the photodetector cells of the 3D photodetector array have a highly consistent performance. In addition, the device can execute the functions of capturing a real‐time light trajectory and identifying multipoint light spatial distribution, which cannot be achieved in all the previously reported 2D solar‐blind photodetectors. The results suggest new pathways to fabricate 3D photodetectors from conventional semiconductor films, which may find potential applications in optical positioning, tracking, imaging and communications, etc.     

Narrow band green organic photodiodes for imaging

Accurate color reproduction using image sensors requires four narrow-band absorbing photodetectors (blue, green, yellow and red). Current photodetectors use a broadband photodetector in combination with color filters, which generally do not have sufficient wavelength discrimination for illuminant independent color recognition. We have developed a green-sensitive organic photodetector, in which color selection is achieved using a narrow-absorbing ketocyanine chromophore, coupled with a low finesse electro-optical cavity inducing further spectral narrowing. The optimized device contained a bulk heterojunction light-absorbing layer comprised of a ketocyanine dye blended with [6,6]-phenyl-C₆₁-butyric acid methyl ester. The photodetector had a response full width at half maximum of 80 nm centered around 525 nm, and an external quantum efficiency of 15% at −1.0 V, which is the highest so far reported for a narrow band green-absorbing organic photodetector. The performance of this detector is sufficient to meet the specifications required by machine vision systems.     

高速、大饱和输出光电流1·55μm波段光电探测器的研究进展及其在光控相控阵雷达中的应用

光控相控阵雷达相对于传统机械式雷达和相控阵雷达,具有更加优异的性能,可适应未来国际形势和军事上的发展需求。光电探测器作为光控相控阵雷达上的关键组件,在整个雷达系统中起着非常重要的作用,直接决定了输出微波信号的质量和雷达探测的最终效果。本文从光控相控阵雷达的基本技术需求出发分析了1．55μm波段光电探测器的必要性和重要性,并且综述了当今国际国内高速、大饱和输出光电流光电探测器的现状,指出了其未来的发展方向。     

Optimization of Solubility,Film Morphology and Photodetector Performance by Molecular Side‐Chain Engineering of Low‐Bandgap Thienothiadiazole‐Based Polymers

A series of donor–acceptor (D‐A) type low‐bandgap polymers containing the terthiophene and thieno[3,4‐b]thiadiazole units in the main chain but different numbers of identical side chains are designed and synthesized in order to study the effect of side chain on the polymer properties and optimize the performance of polymer photodetectors. Variation in the side chain content can influence the polymer solubility, molecular packing, and film morphology, which in turn affects the photodetector performance, particularly with regard to the photoresponsivity and dark current. X‐ray diffraction patterns indicate that molecular ordering increases with more side chains. Atomic force microscopy shows that appropriate morphology of the active layer in the polymer photodetector is necessary for high photocurrent and low dark current. Using BCP as a hole blocking layer (10 nm), the photodetector based on P4 exhibits the optimized performance with specific detectivity of 1.4 × 10¹² Jones at 800 nm, which is among the best reported values for polymer photodetectors and even comparable to that of a silicon photodetector.     

Polarization sensitive photodetector based on quasi-1D ZrSe3

The in-plane anisotropy of transition metal trichalcogenides (MX₃) has a significant impact on the molding of materials and MX₃ is a perfect choice for polarized photodetectors. In this study, the crystal structure, optical and optoelectronic anisotropy of one kind of quasi-one-dimensional (1D) semiconductors, ZrSe₃, are systematically investigated through experiments and theoretical studies. The ZrSe₃-based photodetector shows impressive wide spectral response from ultraviolet (UV) to near infrared (NIR) and exhibits great optoelectrical properties with photoresponsivity of 11.9 mA·W^-1 and detectivity of ~10⁶ at 532 nm. Moreover, the dichroic ratio of ZrSe₃-based polarized photodetector is around 1.1 at 808 nm. This study suggests that ZrSe₃ has potential in optoelectronic applications and polarization detectors.     

Solution‐Processed Self‐Powered Transparent Ultraviolet Photodetectors with Ultrafast Response Speed for High‐Performance Communication System

Transparent ultraviolet (UV) photodetectors are an essential component of next‐generation “see‐through” electronics. However, the current photodetectors often suffer from relatively slow response speeds and high driving voltages. Here, all‐solution‐processed UV photodetectors are reported that are facilely prepared from environmentally friendly and abundant materials. The UV photodetectors are composed of a titanium dioxide thin film as the photosensitive layer sandwiched between two different transparent electrodes to form asymmetric Schottky junctions. The photodetector with high optical transparency can operate at zero bias because of spontaneous separation of photogenerated electron–hole pairs by the built‐in electric field. The resulting self‐powered photodetector displays high sensitivity to broadband UV light (200–400 nm). In particular, an ultrafast response speed up to 44 ns is obtained, representing a significant improvement over those of the conventional transparent photodetectors. Moreover, the photodetector has been successfully applied, for the first time, in a UV communication system as the self‐powered signal receiver. This work uniquely combines the features of high optical transparency and self‐power ability into UV photodetectors and would enable a broad range of optoelectronic applications.     

Modeling and performance of wafer-fused resonant-cavity enhancedphotodetectors

We discuss wavelength tuning and its corresponding quantum efficiency modulated by the standing wave effects in a resonant-cavity enhanced (RCE) photodetector. Specific design conditions are made for a thin In_0.53Ga_0.47As (900 Å) photodetector wafer-fused to a GaAs-AlAs quarter wavelength stacks (QWS). Analytic expressions for the calculation of resonant wavelength and standing wave effects are derived, using a hard mirror concept of fixed phase upon reflection, and are found to agree reasonably well with the exact numerical approach, using a transmission matrix method. We then experimentally demonstrate that wavelength tuning as large as 140 nm and its corresponding quantum efficiency modulated by the standing wave effects are clearly observed in our wafer-fused photodetectors, consistent with the predictions. The external quantum efficiency at 1.3 μm wavelength and absorption bandwidth for the wafer-fused RCE photodiodes integrated with an amorphous Si-SiO₂ dielectric mirror are measured to be 94% and 14 nm, respectively. This technique allows the formation of multichannel photodetectors with high quantum efficiency and small crosstalk, suitable for application to wavelength demultiplexing and high-speed, high-sensitivity optical communication systems     

Analysis and circuit modeling of waveguide-separated absorption charge multiplication-avalanche photodetector (WG-SACM-APD)

Waveguide photodetectors are considered leading candidates to overcome the bandwidth efficiency tradeoff of conventional photodetectors. In this paper, a theoretical physics-based model of the waveguide separated absorption charge multiplication avalanche photodetector (WG-SACM-APD) is presented. Both time and frequency modeling for this photodetector are developed and simulated results for different thicknesses of the absorption and multiplication layers and for different areas of the photodetector are presented. These simulations provide guidelines for the design of these high-performance photodiodes. In addition, a circuit model of the photodetector is presented in which the photodetector is a lumped circuit element so that circuit simulation of the entire photoreceiver is now feasible. The parasitics of the photodetector are included in the circuit model and it is shown how these parasitics degrade the photodetectors performance and how they can be partially compensated by an external inductor in series with the load resistor. The results obtained from the circuit model of the WG-SACM-APD are compared with published experimental results and good agreement is obtained. This circuit modeling can easily be applied to any WG-APD structure. The gain-bandwidth characteristic of WG-SACM-APD is studied for different areas and thicknesses of both the absorption and the multiplication layers. The dependence of the performance of the photodetector on the dimensions, the material parameters and the multiplication gain are also investigated.     

超宽带高饱和单行载流子光探测器研究 （特邀）

超宽带单行载流子（UTC）光电探测器因其仅需快速的电子输运过程,较传统PIN探测器具有明显宽带优势,是6G宽带无线通信、太赫兹成像、超宽带噪声发生器等亚太赫兹频段系统中的核心光电子器件之一。面向亚太赫兹频段光电转换需求,针对UTC探测器中大带宽与高饱和功率之间的矛盾问题,分别研究并突破了光生载流子高速输运机理、感性共面波导器件（CPW）结构等关键技术,研制成功带宽106 GHz、饱和输出功率7.3 dBm的双漂移层结构MUTC探测器芯片,和带宽超过150 GHz的超宽带MUTC探测器芯片。     

Ultrahigh‐Performance Flexible and Self‐Powered Photodetectors with Ferroelectric P(VDF‐TrFE)/Perovskite Bulk Heterojunction

Flexible and self‐powered perovskite photodetectors attract widespread research interests due to their potential applications in portable and wearable optoelectronic devices. However, the reported devices mainly adopt an independent layered structure with complex fabrication processes and high carrier recombination. Herein, an integrated ferroelectric poly(vinylidene‐fluoride‐trifluoroethylene) (P(VDF‐TrFE)) and perovskite bulk heterojunction film photodetector on the polyethylene naphthalate substrate is demonstrated. Under the optimum treatment conditions (the polarization voltage and time, and the concentration of P(VDF‐TrFE)), the photodetector exhibits a largely enhanced performance compared to the pristine perovskite device. The resulting device exhibits ultrahigh performance with a large detectivity (1.4 × 10¹³ Jones) and fast response time (92/193 µs) at the wavelength of 650 nm. The improved performance is attributed to the fact that the polarized P(VDF‐TrFE)/perovskite hybrid film provides a stronger built‐in electric field to facilitate the separation and transportation of photogenerated carriers. These findings provide a new route to design self‐powered photodetectors from the aspect of device structure and carrier transport.     

Travelling-wave photodetectors with 172-GHz bandwidth and 76-GHzbandwidth-efficiency product

Results of the first fabrication and measurement of travelling-wave photodetectors are reported. The devices have bandwidths as high as 172 GHz, the highest reported for a p-i-n photodetector, and bandwidth-efficiency products as large as 76 GHz, the largest reported for any photodetector without gain. Comparisons with vertically illuminated and waveguide photodetectors fabricated on the same wafer establish the superior performance of travelling-wave photodetectors. Microwave loss on the travelling-wave photodetector structure is identified as a bandwidth limitation     

金属-半导体-金属(MSM)结构4H-SiC紫外光电探测器的研制

MSM结构探测器具有结构与工艺简单、制备成本低、量子效率高等特点而在探测器应用中得到重视。本文制备了采用镍作为肖特基接触形成的MSM4H—SiC紫外光电探测器，并测量和分析了在不同的偏压下其光电特性。结果表明，该探测器的暗电流非常小，在偏压为15V的时候，漏电流密度约为70nA／cm^2，光电流比暗电流高约2个数量级，其光谱响应表明，其最高光谱响应与380nm的比值约为1000倍，说明该探测器具有良好的紫外可见比。     

光通信波段超高速PIN光电探测器的新进展

对自20世纪90年代以来在InGaAs PIN超高速光电探测器的研究上所取得的进展进行了综述,介绍了传统型的面入射光电探测器、波导型光电探测器、渐变耦合型光电探测器、小平面折射型光电探测器、反射型光电探测器和单极型光电探测器等的新进展,同时也介绍了超高速光电探测器封装结构。探讨了超高速光电探测器的发展趋势。