异质界面数字梯度超晶格对扩展波长InGaAs光电探测器性能的改善

采用气态源分子束外延方法生长了三种不同结构的扩展波长(室温下50%截止波长为2.4μm) In_xGa_(1-x)As光电探测器材料,并制成了台面型器件.材料的表面形貌、X射线衍射摇摆曲线及光致发光谱表明,在InAlAs/InGaAs异质界面处生长数字梯度超晶格可以明显提高材料质量;器件在室温下的暗电流结果显示,直径为300μm的器件在反向偏压为10mV时,没有生长超晶格结构的器件暗电流为0.521μA,而生长超晶格结构的器件暗电流降到0.480μA.同时,在生长In_xAl_(1-x)As组分线性渐变缓冲层之前首先生长一层InP缓冲层也有利于改善材料质量和器件性能.     

AlGaN日盲紫外雪崩光电探测器暗电流研究

为了提高AlGaN日盲紫外雪崩探测器的信噪比,降低暗电流,研制高性能日盲紫外探测器,针对AlGaN日盲紫外雪崩探测器暗电流机制进行了深入研究。首先对传统p-i-n-i-n结构雪崩探测器进行了初步研究,分别设计了GaN和AlGaN的两种雪崩探测器模型,分析了其不同暗电流特性,得到的模拟暗电流特性曲线与实验吻合。在此基础上,针对日盲紫外波段高Al组分AlGaN雪崩探测器,重点分析研究了不同异质界面的负极化电荷、p型有效掺杂以及温度等因素对暗电流的影响。在AlGaN日盲紫外雪崩探测器研究中得到的近零偏工作暗电流为2.510-13 A,在反向138 V左右发生雪崩击穿,雪崩开启电流为18.3 nA左右,击穿电压温度系数约为0.05 V/K,与实验及文献测试结果吻合。     

Dark current characteristics of GaAs metal-semiconductor-metal(MSM) photodetectors

Calculations of the electron and hole components of dark current in a GaAs metal-semiconductor-metal (MSM) photodetector are presented. A quantum-mechanical model for the electron and hole transport behavior in the contact regions which is used to determine dark current as a function of electric field is developed. The model reduces to a conventional thermionic emission model if an ideal barrier transmission coefficient is assumed. In order to assess the accuracy of the model, photodetectors have been fabricated and tested. Theoretical calculations and experimental data are compared, and good agreement is obtained. Possible modifications to enhance the usefulness of the model are discussed     

无平面结敏感区及其栅控光探测器

研制了在平面结内无敏感区的光探测器,测量结果表明其光电流是显著的。在这种器件的基础上,研制了受栅极控制的无平面结敏感区光探测器,实验测量说明这种器件的光电流输出不仅依赖于受光信号,还受到栅极电压信号的控制。这种输出信号受到光与电信号双重控制的特性,扩大了光探测器件的应用领域。     

改进器件工艺降低硅光电探测器暗电流

为降低硅光电探测器ＰＮ结反向暗电流，可在器件制作工艺中采用一系列完美晶体器件工艺（ＰＣＤＴ）。在实验过程中，对吸除工艺，应力补偿工艺等作了改进，进一步降低了反向暗电流。     

In2Ge2O7薄膜制备及其紫外光敏特性研究

以In2O3和GeO2为原料,采用碳还原法制备了In2Ge2O7多晶薄膜,利用XRD和SEM对薄膜的结构和形貌进行了表征。对基于In2Ge2O7薄膜的金属-半导体-金属(MSM)紫外探测器进行了紫外光电导特性测量,结果显示:在波长为250nm的紫外光照射下,在5V偏压下,器件的光电流为727μA(暗电流为12μA),光响应度达到262.9A.W-1,光响应上升时间约为67s,下降时间约为15s。分析认为较长的响应时间是由于内部的缺陷与位错造成的。初步研究结果表明:In2Ge2O7薄膜可以作为一种良好的日盲紫外探测材料。     

Terahertz Semiconductor Quantum Well Devices

For eventually providing terahertz science with compact and convenient devices,terahertz (1～10THz) quantum-well photodetectors and quantum-cascade lasers are investigated. The design and projected detector performance are presented together with experimental results for several test devices,all working at photon energies below and around optical phonons. Background limited infrared performance (BLIP) operations are observed for all samples (three in total) ,designed for different wavelengths. BLIP temperatures of 17,13, and 12K are achieved for peak detection frequencies of 9.7THz(31μm) ,5.4THz(56μm) ,and 3.2THz(93μm) ,respectively. A set of THz quantum-cascade lasers with identical device parameters except for doping concentration is studied. The δ-doping density for each period varies from 3.2 × 1010 to 4. 8 × 1010cm-2. We observe that the lasing threshold current density increases monotonically with doping concentration. Moreover, the measurements for devices with different cavity lengths provide evidence that the free carrier absorption causes the waveguide loss also to increase monotonically. Interestingly the observed maximum lasing temperature is best at a doping density of 3.6 × 1010cm-2.     

Resonant Terahertz InSb Waveguide Device for Sensing Polymers

We have demonstrated the possibility of employing a device, designed to operate at terahertz (THz) frequencies, for sensing materials. The device consists of a waveguide section with a pair of stubs located at the middle and oriented transversely to the waveguide axis. The two stubs function as a resonator and, hence, the device would behave as a filter in the THz domain. The device was fabricated by laser micromachining of InSb pellets and was characterized by THz time-domain transmission spectroscopy. For a waveguide width of 740 μm and stub length of 990 μm, a transmission minimum is seen to occur at 0.265 THz. We investigated the capability of the device to sense polystyrene, dissolved in toluene, loaded into the stubs. The consequent change in the refractive index in the stubs alters the transmitted signal intensity. Our results show that, a change in concentration of polystyrene even by 1 mol/L, leads to measurable change in the transmission coefficient close to the resonant frequency of the device. Thus, our device operating at THz frequencies shows promising potential as chemical and bio sensors.     

36-GHz High-Responsivity Ge Photodetectors Grown by RPCVD

We present high-speed Ge p-i-n photodetectors for vertical incidence with high responsivity, grown by reduced pressure chemical vapor deposition. From the high-resolution X-ray diffraction analysis, the Ge epilayer shows good crystalline homogeneity and the residual tensile strain of 0.16%. The fabricated device exhibits the 3-dB bandwidth of 36 GHz, the responsivity of 0.47 A/W, and low dark current of 42 nA at $lambda sim 1.55 mu$m. The same device also shows the responsivity of 0.7 A/W at $lambda sim 1.31 mu$m. The on-chip measurement of the eye diagram shows a good opening at 40-Gb/s data transmission.      

X-ray Sensitive hybrid organic photodetectors with embedded CsPbBr3 perovskite quantum dots

X-ray detection is an important technology for medical diagnosis as well as industrial and security inspections. While today's commercial X-ray detectors are bulky, photodetectors based on organic semiconductors have attracted increasing attention owing to their low temperature processing capabilities, flexibility and low cost. Nonetheless, the low X-ray attenuation coefficient of organic semiconductors still hinders their practical application. Herein, a new organic-inorganic hybrid strategy is proposed to improve the X-ray sensitivity of organic photodetectors (OPDs). A solution-processed X-ray sensitive hybrid OPD is fabricated by embedding CsPbBr₃ quantum dots (QDs) into a P3HT:PC₆₁BM bulk heterojunction photodiode. The QDs, acting as embedded scintillators in the organic active layer, maintain a high radioluminescence. The proposed hybrid structure enables indirect X-ray detection in a comprehensive manner. These hybrid photodetectors exhibit suppressed dark current densities in the range of tens of picoamperes per square centimeters for different weight ratios of blended QDs. The best OPD achieves a sensitivity of 229.6 e nGy⁻¹ mm⁻² (3.67 μC Gy⁻¹ cm⁻²) and a dark current of 23.3 pA cm⁻² at a low operating voltage (−3 V) for 20–80 kV “soft” X-rays, thus representing great potential for the development of next generation low cost, portable, and highly sensitive X-ray detectors.     

QUANTUM MECHANICAL MODEL AND SIMULATION OF GaAs/AlGaAs QUANTUM WELL INFRARED PHOTO- DETECTOR-Ⅰ OPTICAL ASPECTS

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｆｒａｒｅｄｄｅｔｅｃｔｏｒｔｅｃｈｎｉｑｕｅｈａｓｂｅｅｎａｋｅｙｆａｃｔｏｒｉｎｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｔｈｅｉｎｆｒａｒｅｄｔｅｃｈｎｏｌｏｇｙｆｏｒｍｏｒｅｔｈａｎ 4 0 ｙｅａｒｓ .Ｓｉｎｃｅ 1970 ,ｓｅｍｉｃｏｎｄｕｃｔｏｒｓｌｉｋｅＩｎＳｂａｎｄＨｇＣｄＴｅｈａｖｅｂｅｅｎｔｈｅｐｒｉｎｃｉｐａｌｍａｔｅｒｉａｌｓｆｏｒｖａｒｉｏｕｓｉｎｆｒａｒｅｄｄｅｔｅｃｔｏｒａｐｐｌｉｃａｔｉｏｎｓ .Ｔｈｅｆｏｒｍａｔｏｆｔｈｅｉｎｆｒａｒｅｄｄｅｔｅｃｔｏｒｍｏｔｉｖａｔｅｄｂｙｓｍａｒｔｔｈｅｒｍａｌｉｍａｇｉｎｇｓｙｓｔｅｍｃｈａｎｇｅｄｆｒｏｍｓｉｎｇｌｅｅｌｅｍｅｎｔｄｅｖｉｃｅｔｏｆｏｃａｌｐｌａｎａｒｒａｙｓ(ＦＰＡｓ)ｉｎｔｈｅｍｉｄｄｌｅｏｆ 80’ｓ [1].Ｔｏｄａｙ’ｓｔｅｃｈｎｏｌｏｇｙｏｆｉｎｆｒａｒｅｄｄｅｔｅｃｔｏｒｃｏｎｃｅｎｔｒａｔｅｓｌａｒｇｅｌｙｏｎｆｏｃａｌｐｌａｎａｒｒａｙｓ ,ｅｘｐｅｃｉａｌｌｙｆｏｒｓｅｎｓｉｔｉｖｅ ,ｈｏｍｏｇｅｎｅｏｕｓａｎｄｌａｒｇｅｆｏｒｍａｔｓｃａｌｅｄｅｖｉｃｅｓ .ＨｇＣｄＴｅ...     

High-Performance van der Waals Metal-Insulator-Semiconductor Photodetector Optimized with Valence Band Matching

The vertical metal-insulator-semiconductor (MIS) photodetectors based on van der Waals heterostructures (vdWHs), fabricated by rationally stacking different layers without the limit of lattice-match, have attracted broad interest due to their wide wavelength monitoring range, high responsivity, high detectivity, and fast response. Here, for the first time, the control of barrier height in vdWHs MIS photodetectors is systematically investigated. Optimizing semiconducting and insulating layers enables lowering the hole barrier height to achieve a high performance of the device. Graphene/hexagonal boron nitride (h-BN)/SnS₂ device shows the best photodetection performance compared to the other common 2D semiconductors. The lowest barrier height ensures that the photo-induced holes transfer efficiently to the graphene electrode and the dark current is highly suppressed by the h-BN layers. Consequently, the graphene/h-BN/SnS₂ MIS photodetectors have a high photoresponsivity of 2 A W⁻¹, a high detectivity of 10¹³ Jones, and a photocurrent/dark current ratio of 5.2 × 10⁵ at a low applied bias of −0.6 V. The highest detectivity reaches 9.6 × 10¹³ Jones which is 100–1000 times greater than previously reported vdWHs MIS photodetectors.     

A novel device for detecting the polarization direction of linear polarized light using integrated subwavelength gratings and photodetectors

A solid-state device that can be used to detect the polarization direction of linear polarized light is proposed. The device consists of six transmission gratings with periods in the subwavelength region of the incident light and six photodetectors integrated separately underneath each grating. A variable, defined through the photocurrent ratios of the grating-photodetector pairs, shows a one-to one correspondence with the angle between the electric vector of the incident linear polarized light and the orientation of the gratings' fingers, which is therefore used to determine the polarization direction. An angular resolution of 0.2/spl deg/ can be achieved.     

High-Detectivity Nitride-Based MSM Photodetectors on InGaN–GaN Multiquantum Well With the Unactivated Mg-Doped GaN Layer

InGaN-GaN multiquantum-well (MQW) metal-semiconductor-metal (MSM) photodetectors (PDs) with the unactivated Mg-doped GaN cap layer were successfully fabricated. It was found that we could achieve a dark current by as much as six orders of magnitude smaller by inserting the unactivated Mg-doped GaN cap layer. For MSM photodetectors with the unactivated Mg-doped GaN cap layer, the responsivity at 380 nm was found to be 0.372 A/W when the device was biased at 5 V. The UV-to-visible rejection ratio was also estimated to be around 1.96 times 10³ for the photodetectors with the unactivated Mg-doped GaN cap layer. With a 5-V applied bias, we found that minimum noise equivalent power and normalized detectivity of our PDs were 4.09 times 10^-14 W and 1.18 times 10¹³ cmmiddotHz^0.5W^-1, respectively. Briefly, incorporating the unactivated Mg-doped GaN layer into the PDs beneficially brings about the suppression of dark current and a corresponding improvement in the device characteristics.     

Tunable TiO2 films for high-performing transparent Schottky photodetector

We demonstrate the transparent Schottky photodetector of the configuration Cu/TiO₂/FTO unveiling superior photodetection properties. The improved performance of fabricated photodetector was ascribed to high quality rutile-nanocrystalline TiO₂ films with very high absorption coefficient (~6×10⁵ cm⁻¹) and excitonic localized states. The existence of such localized states in TiO₂ Schottky device offered fastest response time of 1.12 ms suggesting their application in fast switching photodetectors. In addition, the photodetectors showed high responsivity of the value 0.897 A/W and detectivity 4.5×10¹² Jones. This transparent TiO₂ design would provide a functional route for various photoelectric device applications.     

High Responsivity and Response Speed Single‐Layer Mixed‐Cation Lead Mixed‐Halide Perovskite Photodetectors Based on Nanogap Electrodes Manufactured on Large‐Area Rigid and Flexible Substrates

Mixed‐cation lead mixed‐halide perovskites are employed as the photoactive material in single‐layer solution‐processed photodetectors fabricated with coplanar asymmetric nanogap Al–Au and indium tin oxide–Al electrodes. The nanogap electrodes, bearing an interelectrode distance of ≈10 nm, are patterned via adhesion lithography, a simple, low‐cost, and high‐throughput technique. Different electrode shapes and sizes are demonstrated on glass and flexible plastic substrates, effectively engineering the device architecture, and, along with perovskite film and material optimization, paving the way toward devices with tunable operational characteristics. The optimized coplanar nanogap junction perovskite photodetectors show responsivities up to 33 A W^?1, specific detectivity on the order of 10¹¹ Jones, and response times below 260 ns, while retaining a low dark current (0.3 nA) under ?2 V reverse bias. These values outperform the vast majority of perovskite photodetectors reported so far, while avoiding the complicated fabrication steps involved in conventional multilayer device structures. This work highlights the promising potential of the proposed asymmetric nanogap electrode architecture for application in the field of flexible optoelectronics.     

Silicon-on-Insulator CWDM Power Monitor/Receiver With Integrated Thin-Film InGaAs Photodetectors

In this letter, we demonstrate a compact and cost-effective four-channel demultiplexer with integrated photodetectors for application in coarse wavelength-division-multiplexing systems. The device consists of a silicon-on-insulator planar concave grating (PCG) demultiplexer and heterogeneously integrated InAlAs-InGaAs metal-semiconductor-metal photodetectors, and has a footprint of only 0.1 mm² . The PCG and integrated photodetectors have a responsivity of 0.6 A/W for TE-polarized light. The integrated device has an optical crosstalk of -25 dB.     

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。     

Capillary‐Bridge Mediated Assembly of Conjugated Polymer Arrays toward Organic Photodetectors

Large‐scale patterning of high‐quality organic semiconductors is crucial for the fabrication of optoelectronic devices with high efficiency and low cost. Yet, owing to the uncontrollable dewetting dynamics of organic liquid in conventional solution patterning techniques, large defect density of organic architectures is inevitable, which is detrimental to the device performance. To address this challenge, herein a capillary‐bridge‐mediated assembly technique is developed for regulating the dewetting process, yielding large‐scale 1D microstructure ordered arrays. The 1D arrays organic photodetectors exhibit a high optoelectronic performance of light on/off ratio exceeding 100, responsivity of 3.24 A W^?1, detectivity of 3.20 × 10¹¹ Jones and fast response speed, showing a great improvement compared with spin‐coated membrane devices. In addition, the significant enhancement of the device photodetection under the electronic field modulation is investigated by applying a back‐gate voltage and explained with the photocurrent predominating in the OFF state and the neglected thermocurrent and tunneling current promoting in the ON state of the phototransistor devices. The research offers a new insight for the facile fabrication of large‐scale integrated photodetectors and other organic devices based on patterned conjugated polymers.     

Solution-processed near-infrared polymer photodetectors with an inverted device structure

Solution-processed near-infrared polymer photodetectors with an inverted device structure were designed and fabricated. By introducing ZnO_x and MoO₃ as an electron extraction layer and a hole extraction layer, respectively, the asymmetric characteristics of the inverted polymer photodetectors was constructed. Operating at room temperature, the inverted polymer photodetectors exhibited the detectivity over 10¹² cm Hz^1/2/W from 400 to 850 nm, resulting from the enhanced photocurrent and reduced dark current induced by fabricating photoactive layer from solution with processing additive 1,8-diiodooctane. These device performances were comparable to those of inorganic counterparts.