High-speed Photodiodes Research Articles

Focused microstructure analysis and fabrication for monolithic integration with high-speed MUTC photodiode

Back-incidence high-speed photodiodes with small mesa diameter use back-integrated microstructures, which utilize the convergence and high transmittance function of the microstructures on the light beam to compensate for the incident light alignment deviation and improve the optical coupling efficiency. Two kinds of microstructures integrated with the modified uni-traveling-carrier photodiode (MUTC-PD), microlens and two-dimensional concentric annular convergence grating, are designed theoretically and compared by simulation. It is found that the microlens have better optical performance when integrated. InP microlenses meeting the requirements were fabricated using the photoresist hot melt method and inductively coupled plasma (ICP) etching. Testing revealed that the microlens could reduce the incident light spot size to one-third of its original size. By optimizing the thickness and doping concentration of the PD layer structure, and prepared a high-speed MUTC-PD with monolithic integrated InP microlens, with a mesa diameter of 18 μm. The measured 3 dB bandwidth of the integrated chip is 43 GHz. Experimental results using incident light fiber movement showed that the responsivity of the integrated microlens MUTC-PD increased by 66.76 % when horizontally offset by 10 μm compared to the non-integrated microlens case. When shifted vertically by 20 μm, the MUTC-PD responsivity of the integrated microlens decreases to 83.7 % of the maximum value, which is 18.2 % higher than that of the one without integrated microlens.

In-Situ Quality Intelligent Classification of Additively Manufactured Parts Using a Multi-Sensor Fusion Based Melt Pool Monitoring System

Although laser powder bed fusion (LPBF) technology is considered one of the most promising additive manufacturing techniques, the fabricated parts still suffer from porosity defects, which can severely impact their mechanical performance. Monitoring the printing process using a variety of sensors to collect process signals can realize a comprehensive capture of the processing status; thus, the monitoring accuracy can be improved. However, existing multi-sensing signals are mainly optical and acoustic, and camera-based signals are mostly layer-wise images captured after printing, preventing real-time monitoring. This paper proposes a real-time melt-pool-based in-situ quality monitoring method for LPBF using multiple sensors. High-speed cameras, photodiodes, and microphones were used to collect signals during the experimental process. All three types of signals were transformed from one-dimensional time-domain signals into corresponding two-dimensional grayscale images, which enabled the capture of more localized features. Based on an improved LeNet-5 model and the weighted Dempster-Shafer evidence theory, single-sensor, dual-sensor and triple-sensor fusion monitoring models were investigated with the three types of signals, and their performances were compared. The results showed that the triple-sensor fusion monitoring model achieved the highest recognition accuracy, with accuracy rates of 97.98%, 92.63%, and 100% for high-, medium-, and low-quality samples, respectively. Hence, a multi-sensor fusion based melt pool monitoring system can improve the accuracy of quality monitoring in the LPBF process, which has the potential to reduce porosity defects. Finally, the experimental analysis demonstrates that the convolutional neural network proposed in this study has better classification accuracy compared to other machine learning models.

Pyroelectric-Accelerated Perovskite Photodetector for Picosecond Light Detection and Ranging.

Light detection and ranging (LiDAR) is indispensable in applications such as unmanned aerial vehicles, autonomous driving, and biomimetic robots. However, the precision and available distance of LiDAR are constrained by the speed and sensitivity of the photodetector, necessitating the use of expensive and energy-consuming avalanche diodes. To address these challenges, in this study, a pyroelectricity-based acceleration strategy with 2D-(graded 3D) perovskite heterojunction is proposed to achieve a record high speed (27.7 ns with an active area of 9 mm2, and 176 ps with an active area of 0.2 mm2) and high responsivity (0.65 A W-1) at zero bias. This success is attributed to the unique mechanism where the electrons from the pyroelectric effect at the Cl-rich 2D/3D interface directly recombine with excess holes during light-dark transitions, breaking speed limitations related to carrier mobility and capacitive effect. Furthermore, the introduced pyroelectric effect significantly enhances the photoresponse, resulting in a self-powered external quantum efficiency exceeding 100%. The study also demonstrates precise position detection at the centimeter level. In conclusion, this research presents a pioneering approach for developing high-speed photodiodes with exceptional sensitivity, mitigating energy and cost concerns in LiDAR applications.

Cryogenic Fiber-coupled Electro-optic Characterization Platform for High-speed Photodiodes

We have developed a cryogenic characterization platform for ultrafast photodiodes, whose time domain responses are extracted by electro-optic sampling using femtosecond laser pulses in a pump-probe configuration. The excitation of the photodiodes with the pump beam and the electro-optic sampling crystals with the probe beam are realized in a fully fiber-coupled manner. This allows us to use the characterization platform at different temperatures, ranging from cryogenic to room temperature. As an application example, we characterize the time-domain response of commercial p-i-n photodiodes with a nominal bandwidth of 20 GHz and 60 GHz at temperatures of 4 K and 300 K and in a large parameter range of photocurrent and reverse bias. For these photodiodes, we detect frequency components up to approximately 250 GHz, while the theoretical bandwidth of our sampling method exceeds 1 THz. Our measurements demonstrate a significant excitation power and temperature dependence of the photodiodes’ ultrafast time responses, reflecting, most likely, changes in carrier mobilities and electric field screening. Since our system is an ideal tool to characterize and optimize the response of fast photodiodes at cryogenic temperatures, it has a direct impact on applications in superconducting quantum technology such as the enhancement of optical links to superconducting qubits and quantum-accurate waveform generators.

Segmental Measurement of High-speed Photodiodes Based on Pre-definable Electro-optic Frequency Comb

Segmental Measurement of High-speed Photodiodes Based on Pre-definable Electro-optic Frequency Comb

Wide dynamic range photodiodes for microwave photonics and comunication systems

The influence of the design of high-speed photodiodes for microwave photonics and signal transmission systems on the diode dark current is studied experimentally. It is shown that Schottky barrier photodiodes demonstrate the lowest dark currents, excelling photodiodes of the pin design. Photodiodes of 25 micron mesa diameter with the dark current average value as low as 0.4 mA have been manufactured. It is shown the dark current value is controlled by the mesa side wall leakage.

Using wafer scale ferroelectric domains of LiNbO3 to form permanent planar p–n junction in narrow band gap nanocrystals

p–n junctions based on nanocrystals now serve as fundamental components in optoelectronics. However, the process of designing these p–n junctions has largely relied on empirical choices, either for ligand exchange or for the selection of charge transport layers. Therefore, a systematic strategy is still lacking. In this study, we explore the utilization of ferroelectric domains as a general method for remotely inducing the formation of a p–n junction. To ensure compatibility with devices of various designs, we employ a commercially available periodically poled LiNbO3 (PPLN) substrate commonly used in nonlinear optics. We engineer a PPLN/graphene/HgTe heterostructure and demonstrate its planar photodiode behavior. Through x-ray photoemission microscopy, we confirm that the rectifying behavior stems from the influence of the ferroelectric domains, by ruling out the possibility of the formation of non-ohmic contacts at the electrode/semiconductor interfaces. This approach proves to be quite general and holds promise for the future design of high-speed nanocrystal-based photodiodes.

High-speed flexible near-infrared organic photodiode for optical communication.

Optical communication is a particularly compelling technology for tackling the speed and capacity bottlenecks in data communication in modern society. Currently, the silicon photodetector plays a dominant role in high-speed optical communication across the visible-near-infrared spectrum. However, its intrinsic rigid structure, high working bias and low responsivity essentially limit its application in next-generation flexible optoelectronic devices. Herein, we report a narrow-bandgap non-fullerene acceptor (NFA) with a remarkable π-extension in the direction of both central and end units (CH17) with respect to the Y6 series, which demonstrates a more effective and compact 3D molecular packing, leading to lower trap states and energetic disorders in the photoactive film. Consequently, the optimized solution-processed organic photodetector (OPD) with CH17 exhibits a remarkable response time of 91ns (λ = 880nm) due to the high charge mobility and low parasitic capacitance, exceeding the values of most commercial Si photodiodes and all NFA-based OPDs operating in self-powered mode. More significantly, the flexible OPD exhibits negligible performance attenuation (<1%) after bending for 500 cycles, and maintains 96% of its initial performance even after 550h of indoor exposure. Furthermore, the high-speed OPD demonstrates a high data transmission rate of 80MHz with a bit error rate of 3.5 [Formula: see text] 10-4, meaning it has great potential in next-generation high-speed flexible optical communication systems.

Compact OWC Receiver: Micro-Lens and PD Array on Glass Interposer

In this paper, we propose a compact optical wireless receiver based on micro-lens and photodiode array flip-chipped on a glass interposer. With simulation models and experiments, we verify the performance of two optical wireless communication receivers assembled based on this structure with gigabit and high-speed photodiodes. First, co-integrated gigabit photodiodes and micro-lenses indicate that micro-lenses can deliver a 3.5 dB gain of light collection efficiency to the gigabit photodiode array while keeping the field of view larger than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 18 degrees. Besides, a 5.5 Gbps maximum throughput has been verified by this optical wireless communication receiver with discrete multitone modulation. Moreover, co-integrated high-speed photodiodes and micro-lenses prove that micro-lenses realize a 26.6 dB improvement in light collection efficiency, enabling a 10 Gbps error-free connection using as little as -0.5 dBm transmission power. Those results conclude that the co-integration of micro-lenses on the photodiode array can enhance the light collection efficiency of the photodiode array while keeping a larger field of view, providing a high-performance, low-cost solution for the receiver of optical wireless links.

Analysis of the Effect of Radiation Defects by Low-energy Protons on Electrophysical Properties of Silicon N+ -P-P+Structure

Nowadays, radiation engineering is a promising direction in the creation of semiconductor devices. The proton irradiation is used to controllably change the optical, electrical, recombination, mechanical and structural properties of the semiconductors. Low-energy protons make it possible to purposefully change material properties near the surface where the n+ -p junction is located. In this paper, the impact of low-energy protons on the electro physical parameters of n+ -p-p+ silicon photoelectric converters (SPC) is analyzed. The current-voltage characteristics and switching time of these SPCs are measured. The switching time is determined using rectangular bipolar voltage pulses with an amplitude of 10 mV, a frequency of 200 kHz, or a frequency of 1 MHz. A theoretical and experimental analysis of the obtained results is performed. The comparison of experimental data with the results of calculations shows that protons with an energy of 180 keV and a dose of 1015 cm–2 create two regions in the space charge region of the n+ -p junction with different switching times of 4.2 × 10–7 s and 5.5 × 10–8 s. SPC frequency characteristics have been improved by reducing the effective lifetime by 5-10 times. This effect can be used to create high-speed photodiodes with an operating modulation frequency of 18 MHz.

Study of displacement damage effects in InGaAs PIN photodiode under 10 MeV proton irradiation

The displacement damage effect of 10 MeV proton radiation on a high-speed InGaAs PIN photodiode has been experimentally investigated to evaluate the stability of the device in a space radiation environment. The results show that the dark current and low-frequency noise of the device increase significantly after irradiation, while the capacitance of the device decreases slightly after irradiation, where the spectral response parameters are less affected by irradiation. The increase in dark current is essentially linear with the displacement damage dose. Finally, the effect of proton irradiation on the optical communication system is simulated and the results show that the bit error rate of the system increases with the increase in irradiation fluence, which seriously affects the sensitivity of the optical communication system.

The photodetection of ultrashort optical pulse trains for low noise microwave signal generation.

Electrical signals derived from optical sources have achieved record-low levels of phase noise, and have demonstrated the highest frequency stability yet achieved in the microwave domain. Attaining such ultrastable phase and frequency performance requires high-fidelity optical-to-electrical conversion, typically performed via a high-speed photodiode. This paper reviews characteristics of the direct photodetection of optical pulses for the intent of generating high power, low phase noise microwave signals from optical sources. The two most popular types of photodiode detectors used for low noise microwave generation are discussed in terms of electrical pulse characteristics, achievable microwave power, and photodetector nonlinearities. Noise sources inherent to photodetection, such as shot noise, flicker noise, and photocarrier scattering are reviewed, and their impact on microwave phase fidelity is discussed. General guidelines for attaining the lowest noise possible from photodetection that balances power saturation, optical amplification, and amplitude-to-phase conversion, are also presented.

Excess noise factor measurement for low-noise high-speed avalanche photodiodes

The excess noise factor(F) is an important parameter for Avalanche Photodiodes (APDs), indicating the extent to which the noise of the diodes exceeds what it would be without multiplication. This paper presents a method of measuring the excess noise factor for high-speed low-noise APDs using the high-sensitivity spectrum analyzer. The F factor test for the high-speed low-noise APDs was performed by comparing two conditions with and without illumination to remove the interference of the system, including the thermal noise and analyzers. The setup conditions of the light source are analyzed in detail. The F factor was obtained as 3.03 when the multiplication factor M is 10, which corresponds to an effective ionization coefficient ratio k of 0.14 for the high-speed InAlAs APD. For comparison, the k value of a commercial Si APD is tested to be ∼0.06.

Simultaneous enhancement of the bandwidth and responsivity in high-speed avalanche photodiodes with an optimized flip-chip bonding package.

The enhancement in responsivity of photodiodes (PDs) or avalanche photodiodes (APDs) with the traditional flip-chip bonding package usually comes at the expense of degradation in the optical-to-electrical (O-E) bandwidth due to the increase of parasitic capacitance. In this work, we demonstrate backside-illuminated In0.52Al0.48As based APDs with novel flip-chip bonding packaging designed to relax this fundamental trade-off. The inductance induced peak in the measured O-E frequency response of these well-designed and well-packaged APDs, which can be observed around its 3-dB bandwidth (∼30 GHz), effectively widens the bandwidth and becomes more pronounced when the active diameter of the APD is aggressively downscaled to as small as 3 µm. With a typical active window diameter of 14 µm, large enough for alignment tolerance and low optical coupling loss, the packaged APD exhibits a moderate damping O-E frequency response with a bandwidth (36 vs. 31 GHz) and responsivity (3.4 vs. 2.3 A/W) superior to those of top-illuminated reference sample under 0.9 Vbr operation, to attain a high millimeter wave output power (0 dBm at 40 GHz) and output current (12.5 mA at +8.8 dBm optical power). The excellent static and dynamic performance of this design open up new possibilities to further improve the sensitivity at the receiver-end of the next-generation of passive optical network (PON) and coherent communication systems.

Influence of photonic crystals on the performance parameters of GeSn vertical-structure photodiodes

In recent years, use of photonic crystals has been recognized as a viable approach to resolve the contradiction between operating speed and light absorption in vertical-structure photodiodes. In this paper, we present a photonic crystal that enhances the responsivity of a GeSn pin photodiode in the near-infrared region of the spectrum. Additionally, the effects of this photonic crystal on the most important properties of the GeSn photodiodes are studied. Based on measurement and analysis of the device’s dark current, responsivity, and speed characteristics, the photonic crystal structure reduces the dark current by approximately 57%, increases the responsivity at 1550 nm and 1650 nm by factors of 2.4 and 3.9, respectively, and increases the 3dB bandwidth at 1550 nm by a factor of approximately 2.6. These results demonstrate that photonic crystals have good application value for solution of the contradiction between the light absorption and operating speed characteristics of high-speed photodiodes.

Integrated silicon photonic MEMS

Silicon photonics has emerged as a mature technology that is expected to play a key role in critical emerging applications, including very high data rate optical communications, distance sensing for autonomous vehicles, photonic-accelerated computing, and quantum information processing. The success of silicon photonics has been enabled by the unique combination of performance, high yield, and high-volume capacity that can only be achieved by standardizing manufacturing technology. Today, standardized silicon photonics technology platforms implemented by foundries provide access to optimized library components, including low-loss optical routing, fast modulation, continuous tuning, high-speed germanium photodiodes, and high-efficiency optical and electrical interfaces. However, silicon’s relatively weak electro-optic effects result in modulators with a significant footprint and thermo-optic tuning devices that require high power consumption, which are substantial impediments for very large-scale integration in silicon photonics. Microelectromechanical systems (MEMS) technology can enhance silicon photonics with building blocks that are compact, low-loss, broadband, fast and require very low power consumption. Here, we introduce a silicon photonic MEMS platform consisting of high-performance nano-opto-electromechanical devices fully integrated alongside standard silicon photonics foundry components, with wafer-level sealing for long-term reliability, flip-chip bonding to redistribution interposers, and fibre-array attachment for high port count optical and electrical interfacing. Our experimental demonstration of fundamental silicon photonic MEMS circuit elements, including power couplers, phase shifters and wavelength-division multiplexing devices using standardized technology lifts previous impediments to enable scaling to very large photonic integrated circuits for applications in telecommunications, neuromorphic computing, sensing, programmable photonics, and quantum computing.

High-Speed Waveguide-Integrated Avalanche Photodiodes for Near-Infrared Wavelengths on SiN-on-SOI Photonic Platform

Recently, there have been efforts on developing monolithically integrated avalanche photodiodes (APDs) for visible and near-infrared (NIR) wavelengths. However, the fabrication of these detectors in commercial photonic foundries often requires custom integration flow due to many design rule violations in standard integration process. This increases the fabrication cost, hinders the use of highly robust integration platform, and prevents access to well-mature process design kits. Here, we report on waveguide-integrated APDs operating at 850 nm by utilizing a commercial silicon nitride-on-silicon-on-insulator (SiN-on-SOI) photonics platform with no process modifications. Our devices comprise a SiN waveguide for input light routing and an SOI layer underneath to form APDs. We examine the effect of different junction parameters and device length on DC and high-speed device performance. We demonstrate high gain-bandwidth product up to 120 GHz with low dark current of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{&lt; }$</tex-math></inline-formula> 25 nA and high responsivity that can reach 0.71 A/W, and observe open eye diagrams at up to 40 Gbps for all device variations. The performance parameters are on-par or even superior when compared to other integrated APDs operating in the NIR wavelengths. Being compatible with the standard integration flow of a multi-project wafer service of a commercial foundry, our devices are readily accessible, and they expand the functionalities of well-mature SiN-on-SOI photonics platform for applications ranging from optical interconnects, LIDAR, visible light communication to biosensing and quantum applications.

Mechanisms of enhanced sub-bandgap absorption in high-speed all-silicon avalanche photodiodes

All-silicon (Si) photodiodes have drawn significant interest due to their single and simple material system and perfect compatibility with complementary metal-oxide semiconductor photonics. With the help from a cavity enhancement effect, many of these photodiodes have shown considerably high responsivity at telecommunication wavelengths such as 1310 nm, yet the mechanisms for such high responsivity remain unexplained. In this work, an all-Si microring is studied systematically as a photodiode to unfold the various absorption mechanisms. At − 6.4 V , the microring exhibits responsivity up to ∼ 0.53 A / W with avalanche gain, a 3 dB bandwidth of ∼ 25.5 GHz , and open-eye diagrams up to 100 Gb/s. The measured results reveal the hybrid absorption mechanisms inside the device. A comprehensive model is reported to describe its working principle, which can guide future designs and make the all-Si microring photodiode a promising building block in Si photonics.

The ripple-curry amplifier in photonic applications

This paper discusses the new design of a amplifier for the miniature MEMS-type spectrometer. The application problem of the new amplifier was the correct conditioning of the sensor's photoelectric pulses. The processed signal was a sequence of pulses that had variable both frequency and amplitude value. Thus, such a broadband amplifier should have the functionality of automatic gain control. This paper describes the concept of the new circuit, develops its detailed application, and then performs validation tests. Measurement results of the new circuit are discussed in the final section of the paper. Full Text: PDF ReferencesC. Ortolani, Flow Cytometry Today. Detectors and Electronics, (Springer 2022). pp. 97-119, CrossRef D. Maes, L. Reis, S. Poelman, E. Vissers, V. Avramovic, M. Zaknoune, G. Roelkens, S. Lemey, E. Peytavit, B. Kuyken, "High-Speed Photodiodes on Silicon Nitride with a Bandwidth beyond 100 GHz", Conference on Lasers and Electro-Optics, Optica Publishing Group, (2022). CrossRef R. Das, Y. Xie, A.P. Knights, "All-Silicon Low Noise Photonic Frontend For LIDAR Applications", 2022 IEEE Photonics Conference (IPC), IEEE Xplore (2022). CrossRef FEMTO Messtechnik GmbH, Variable Gain Photoreceiver - Fast Optical Power Meter Series OE-200, DirectLink M. Nehir, C. Frank, S. Aßmann, E.P. Achterberg, "Improving Optical Measurements: Non-Linearity Compensation of Compact Charge-Coupled Device (CCD) Spectrometers", Sensors 19(12), 2833 (2019). CrossRef F. Thomas,; R. Petzold, C. Becker, U. Werban, "Application of Low-Cost MEMS Spectrometers for Forest Topsoil Properties Prediction", Sensors 21(11), 3927 (2021). CrossRef M. Muhiyudin, D. Hutson, D. Gibson, E. Waddell, S. Song, S. Ahmadzadeh, "Miniaturised Infrared Spectrophotometer for Low Power Consumption Multi-Gas Sensing", Sensors 20(14), 3843 (2020). CrossRef S. Maruyama, T Hizawa, K. Takahashi, K. Sawada, "Optical-Interferometry-Based CMOS-MEMS Sensor Transduced by Stress-Induced Nanomechanical Deflection", Sensors 18(1), 138 (2018). CrossRef S. Merlo, P. Poma, E. Crisà, D. Faralli, M. Soldo, "Testing of Piezo-Actuated Glass Micro-Membranes by Optical Low-Coherence Reflectometry", Sensors 17(3), 8 (2017). CrossRef M.S. Wei, F. Xing, B. Li, Z. You, "Investigation of Digital Sun Sensor Technology with an N-Shaped Slit Mask", Sensors 11(10), 9764 (2011). CrossRef Z. Yang, T. Albrow-Owen, W. Cai, T. Hasan, "Miniaturization of optical spectrometers", Science 371, 6528 (2021). CrossRef Hamamatsu Photonics K.K. Fingertip size, ultra-compact spectrometer head integrating MEMS and image sensor technologies. DirectLink Microchip Technology Inc, MCP6291/1R/2/3/4/5 1.0 mA 10 MHz Rail-to-Rail Op Amp, CrossRef Microchip Technology Inc. MCP6021/1R/2/3/4 Rail-to-Rail Input/Output 10 MHz Op Amps, CrossRef

Design of a High-Speed PIN Photodiode With a Gradually-Doped Composite Absorption Layer for 100 Gbit/s Optical Receivers

In this paper, we propose a high-speed PIN photodiode with a composite absorption layer. It supports a 3-dB bandwidth of 43 GHz and can be used in 100 Gbit/s optical receivers. The composite absorption layer consists of a gradually-doped p-type absorption layer and an undoped absorption layer. It has different carrier transport mechanisms from the traditional PIN-PD with a single intrinsic absorption layer. The gradually-doped p-type absorption layer accelerates electron diffusion in the p-type absorption layer. Comparison of three kinds of PIN photodiodes with different absorption layers shows that the proposed PIN-PD provides the highest bandwidth while ensuring satisfactory responsivity. The simulation used a numerical model, calculated by Crosslight APSYS software. The results were compared with the analytical method and obtained a good agreement. This work offers a novel structure and good guidance for the design and optimization of photodiodes.