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We demonstrate a hybrid Si photodetector structure by employing an additional layer of fluorescent carbon quantum dot (CQD) nanoparticles constructed on the surface of a Si positive-intrinsic-negative (PIN) photodetector. The experimental studies reveal that the optimized hybrid device can efficiently enhance short-wavelength range responsibility between 300 nm to 600 nm without inducing any deteriorated photodetection performance beyond the short-wavelength region, and thereby achieve broadband sensitivity across the UV–vis-NIR spectra region. The measured photoresponsivity of the optimized device can achieve ∼0.088 A W−1 (@500 nm), which was ∼25% higher than that of a commercial blank PIN Si photodetector. [ABSTRACT FROM AUTHOR]

This paper reports on a CMOS fully integrated optoelectronic sensing system composed of a Si photodiode and a transimpedance amplifier acting as the electronic analog front-end for the conditioning of the photocurrent generated by the photodiode. The proposed device has been specifically designed and fabricated for wearable/portable/implantable biomedical applications. The massive employment of sensor systems in different industrial and medical fields requires the development of small sensing devices that, together with suitable electronic analog front ends, must be designed to be integrated into proper standard CMOS technologies. Concerning biomedical applications, these devices must be as small as possible, making them non-invasive, comfortable tools for patients and operating with a reduced supply voltage and power consumption. In this sense, optoelectronic solutions composed of a semiconductor light source and a photodiode fulfill these requirements while also ensuring high compatibility with biological tissues. The reported optoelectronic sensing system is implemented and fabricated in TSMC 180 nm integrated CMOS technology and combines a Si photodiode based on a PNP junction with a Si area of 0.01 mm2 and a transimpedance amplifier designed at a transistor level requiring a Si area of 0.002 mm2 capable to manage up to nanoampere input currents generated by the photodiode. The transimpedance amplifier is powered at a 1.8 V single supply showing a maximum power consumption of about 54 μW, providing a high transimpedance gain that is tunable up to 123 dBΩ with an associated bandwidth of about 500 kHz. The paper reports on both the working principle of the developed ASIC and the experimental measurements for its full electrical and optoelectronic characterizations. Moreover, as case-examples of biomedical applications, the proposed integrated sensing system has also been validated through the optical detection of emulated standard electrocardiography and photoplethysmography signal patterns. [ABSTRACT FROM AUTHOR]

Flexible photodetectors are pivotal in contemporary optoelectronic technology applications, such as data reception and image sensing, yet their performance and yield are often hindered by the challenge of heterogeneous integration between photoactive materials and flexible substrates. Here, we showcase the potential of an electrostatic force-assisted transfer printing technique for integrating Si PIN photodiodes onto flexible substrates. This clean and dry process eliminates the need for chemical etchants, making it a highly desirable method for manufacturing high-performance flexible photodetector arrays, expanding their widespread applications in electronic eyes, robotics, and human-machine interaction. As a demonstration, a 5 × 5 flexible Si photodetector focal plane array is constructed for imaging sensors and shaped into a convex semicylindrical form to achieve a π field of view with long-term mechanical and thermal stability. Such an approach provides a high yield rate and consistent performance, with the single photodetector demonstrating exceptional characteristics, including a responsivity of 0.61 A/W, a response speed of 39.77 MHz, a linear dynamic range of 108.53 dB, and a specific detectivity of 2.75 × 10 12 Jones at an applied voltage of -3 V at 940 nm.

In order to investigate the feasibility of applying dye-sensitized solar cells (DSSC) as optical sensors, DSSC and Si photodiode (Si PD) were irradiated by RGB LED with various colors and intensities, and the electrical properties were recorded. The relationships between the electrical properties, color and intensity of light are contrastively analyzed. The open-circuit voltage ( V oc ) of DSSC is larger and much more stable with the variation of light intensity than that of Si PD, while the short-circuit current ( I sc ) of DSSC is relatively smaller than that of Si PD. The colored light is assumed to be monochromatic light with similar color by using conversion algorithm written by Dan Bruton. High relative deviation between the experimental intensity and the calculated incident intensity is found in DSSC and Si PD, confirming the exoterica that RGB-mixed light is not monochromatic in nature though their color is similar. I sc and V oc response time under pulsed irradiation by RGB light were studied, and the results show that I sc rise time of DSSC is ∼150 ms, which is at least three times as long as that of Si PD, and V oc fall time of DSSC is much longer than that of Si PD. [ABSTRACT FROM AUTHOR]

Emerging fluorescent protein-based sensors allow researchers to monitor neural activities via optical recording of the fluorescence signals. This optical method is able to monitor multiple cell signals with ease in identifying individual cells in dense neurocircuitry. To this end, we demonstrate a high-yield passive Si photodiode array, aiming to establish a miniaturized optical recording device toward in-vivo use. Our fabricated array features a high yield (>90%), low detection limit (32 \mu \textW /cm2), and high speed (1000 frames per second for scanning up to 100 pixels). Using a fast I–V measurement setup, we examined the device performance in terms of detection limit and speed. A mapping of the light intensity on the entire array manifests its promise as an on-chip fluorescence imager for optical neural recording. The array routinely consumes sub- 10~\mu \textW power, which is suitable for chronic in vivo use. [ABSTRACT FROM AUTHOR]

A hybrid photodector made by integrating solution-processed ultrathin fluorescent InP/ZnS quantum dots (QDs) layer onto a Si photodetector is demonstracted. The optimized hybrid photodetector achieves favorably enhanced near ultraviolet (NUV) spectral range responsibility from 300 nm to 450 nm without introducing any deteriorated photodetection performance of the Si photodetector beyond short-visible wavelength band. [Display omitted] • A new type of hybrid photodetector made by integrating ultrathin fluorescent InP/ZnS quantum dots layer onto a Si photodetector is demonstrated. • The hybrid photodetector achieves enhanced near ultraviolet spectral range responsibility. • The photoresponsivity of the optimal hybrid device increased by a factor of 6.1 relative to a commercial blank Si based photodetector (@ 390 nm). Silicon (Si) photodetectors are utilized in numerous fields ranging from various optical interconnects via spectroscopy application to industrial process control. Despite this, the generally adopted Si photodetectors tends to be more sensitive to red and near-infrated light than blue and near ultraviolet (NUV) light. Here, a new type of hybrid photodetector made by integrating solution-processed ultrathin fluorescent InP/ZnS quantum dots (QDs) layer onto a Si photodetector is conceived and demonstracted. The optimized hybrid photodetector achieves favorably enhanced near ultraviolet (NUV) spectral range responsibility between 300 nm and 450 nm without introducing any deteriorated photodetection performance of the Si photodetector beyond short-visible wavelength band. The photoresponsivity of the optimal hybrid device reaches 0.022 A/W at the wavelength of 380 nm and increased by a factor of 6.1 relative to a commercial Si based photodetector without additional InP/ZnS QDs ultrathin layer, while simultaneously achieving high on/off ratio under 0 V working voltage. The proposed approach and findings represent a promising strategy in the quest for low-cost and broadband photodetectors with compact architecture that is directly compatible with nowadays integrated circuit technology. [ABSTRACT FROM AUTHOR]

Photodetection with high responsivity at the wavelength of 1060 nm is highly desirable for light detection and ranging (LiDAR) as well as the recent emergence of swept-source optical coherent tomography (SS-OCT) applications. However, the absorption coefficient $\alpha $ of Si material at 1060 nm under the bias of 0 V is very low due to its approach to the absorption bandgap edge of Si material. In this letter, the carrier-collection-enhanced structure is proposed, which functions as multiple carrier collection paths, which enhances the external quantum efficiency of photodiodes. An efficient Si photodiode with responsivity of 0.49 A/W at 1060 nm at 0 V is demonstrated, which is 2.5 times of that of commercial products. The cost-effective fabrication of Si photodiodes greatly enhances the system performance of LiDAR and OCT. [ABSTRACT FROM PUBLISHER]

The advancement of deep reactive-ion etching (DRIE) technology has enabled many 3-D structures, and are widely employed in microelectromechanical systems (MEMS). From an electrical point of view, however, those structures have been used as passive components such as capacitors and resistors. To further evolve the utility of future MEMS devices, the authors propose to integrate "active electrical devices" into 3-D MEMS. As an example, vertical trench photodiodes were fabricated on an n-type bulk silicon wafer using DRIE and thermal diffusion of boron. A photocurrent increase from 25% to 70%, and 20% smaller crosstalk was seen in 40-mm deep-trench diodes, as compared to a planar diode made on the same wafer [ABSTRACT FROM PUBLISHER]

Abstract: The degradation behavior for Si p–i–n photodiodes by neutron irradiation at different temperatures was studied. The degradation of the electrical device performance is more pronounced for low-temperature irradiations. Two electron capture levels at and , respectively, were observed by deep level transient spectroscopy. The degradation of the device performance is correlated with the introduction rate of the radiation-induced lattice defects. [Copyright &y& Elsevier]

Abstract: Ion Beam Induced Charge (IBIC) imaging with a 2MeV He+ microbeam has been used to investigate spectroscopic features and charge transport properties of a Hamamatsu S1223 silicon PIN photodiode. Pulse height spectra were collected with high lateral resolution at different reverse bias values between 0V and −100V. Pulse height maps and median energy maps were generated to observe the spatial variations of charge collection properties. Absolute charge collection efficiency was calculated along a line including the edge structure of the photodiode. Our results show that the charge collection is uniform within the sensitive area of the PIN diode but it is decreasing close to the edges. There are low energy satellite peaks and other structures in the spectra due to energy loss in the edge protecting surface coverages and incomplete charge collection in the near surface and undepleted regions. The investigated effects contribute to the further understanding of the operation of the Si photodiode and similar semiconductor device structures. [Copyright &y& Elsevier]

Results are presented of a detailed study of the effects of high-temperature 4-MeV neutron irradiation on the performance degradation of Si pin photodiodes. The macroscopic device performance is correlated with the radiation-induced defects observed by DLTS. It was found that the dark current increases after irradiation, while the photocurrent decreases. After irradiation, two majority electron capture levels (Ec 0.40 eV) were induced in the n-Si substrate. Additionally, degradation of device performance and the rate of introduction of lattice defects decrease with increasing irradiation temperature. For 250 °C irradiation, the reduction of the photocurrent is only 10% of the starting value. This result suggests that the creation and recovery of radiation damage proceed simultaneously at high temperatures. [Copyright &y& Elsevier]

Results are presented of a detailed study of the effects of high-temperature 4-MeV neutron irradiation on the performance degradation of Si pin photodiodes together with the radiation-induced defects, observed by deep level transient spectroscopy. The degradation of the device performance and the introduction rate of the lattice defects decrease with increasing sample temperature during irradiation. For a 250°C irradiation, the reduction of the reverse current is only 20% of the starting value. This result suggests that the creation and recovery of the radiation damage proceeds simultaneously at high temperatures. Carbon-related complex as hole capture levels is also mainly responsible for the device degradation for high-temperature neutron irradiation. [Copyright &y& Elsevier]