Dark Current Degradation Research Articles

Accelerated dark current degradation study of monolithically integrated In 0.2 Ga 0.8 As/GaAs-on-Si nano-ridge photodetectors

Accelerated dark current degradation study of monolithically integrated In _0.2 Ga _0.8 As/GaAs-on-Si nano-ridge photodetectors

Ionizing Radiation Effects on Hole Collection Backside-Illuminated p-Type Deep-Trench-Pinned Photo-MOS Pixels Under Image Acquisition

Dark current degradation, origins, and annealing behavior after x-ray irradiation are studied in a P-type, hole collecting, backside-illuminated image sensor currently being developed at STMicroelectronics and based on deep-trenched photo-MOS pixels. Different biasing conditions during irradiation, i.e. grounded or biased and sequenced, are compared. The dark current increase with total ionizing dose (TID) and the dark current annealing behavior seem to be driven by the backside interface between the P-epitaxy of the pixels and the ONO stack. Despite still being under development, this pixel architecture already exhibits both very good electro-optical performance and a better radiation hardness than pinned photodiode-based CMOS Image sensors that benefit from the same advanced CIS processing technologies. At high total dose range, the photogate challenges custom Radiation-Hardened-by-Design photodiodes by exhibiting a comparable radiation tolerance while bringing new features such as high-resolution or Correlated Double Sampling.

Electric Field-Enhanced Generation Current in Proton Irradiated InGaAs Photodiodes

Dark current degradation due to 49.7 MeV proton irradiation is studied on lattice-matched InGaAs PIN photodiodes. This degradation is described in terms of electric field enhanced Shockley-Read-Hall generation current in the depletion region. In this paper we present a model of the radiation-induced generation current which includes the role of the electric field through the generation rate field enhancement factor (GRFEF). Using a combination of dark current-voltage ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_d – V</i> ) and capacitance-voltage ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C – V</i> ) measurements, an experimental GRFEF is extracted for the thermal generation rate. This GRFEF has been used to define a new damage factor for InGaAs at low electric field that has been compared to previous literature studies. As a final result, the low-field generation lifetime degradation as a function of the fluence has been extracted.

Multifunctional l-tryptophan derivative induced surface passivation for lateral perovskite photodetectors

Organic-inorganic hybrid perovskites have already been employed as promising light-sensitive materials for high-performance photodetectors (PDs) due to their intriguing optoelectronic features. Nonetheless, such perovskite-based PDs often suffer from low sensitivity, high dark current and inevitable degradation. In this work, a novel multifunctional molecule l-tryptophan ethyl ester hydrochloride (l-TEEH) was used to treat the surface defects of triple-cation mixed halide perovskite film. It is found that the modulator with multiple functional groups can effectively passivate the uncoordinated ions (Pb2+ and I-) and halide (I and Cl) vacancies of the perovskite film. Owing to the reduced defects, the dark current of the pristine perovskite PD significantly decreases from ∼ 10-9 A to ∼ 10-11 A after the l-TEEH treatment. Moreover, the perovskite PD with the l-TEEH treatment exhibits a large photoresponsivity (1.27 A/W) and an ultrahigh on/off ratio (∼9 × 103). More impressively, the optimized device shows excellent stability in air with a relative humidity of 40–50 %. Furthermore, the reliable imaging capability of perovskite device with the l-TEEH treatment is also successfully demonstrated.

Silicon carbide Schottky diode detector for fusion neutron yields monitoring using associated particle method

The associated particle method is proven to be one of ideal options for D-T fusion neutron detection, acquiring accurate neutron yields by monitoring α particle. Semiconductor detectors can be used to detect α particle for compact size, high energy-resolution, and stable response. SiC detector with high radiation resistance is benefit for long service time in fusion neutron monitoring. In this paper, a SiC Schottky diode detector is used to detect associated α particles for D-T fusion neutron monitoring, and successfully gets accurate neutron yields, being highly consistent with the conventional Si surface barrier detector. It is encouraging to find out SiC detector can afford 2.56 × 109 cm−2 α particles irradiation, with slight performance degradation of dark current and energy resolution, indicating that SiC detector is a promising candidate for fusion neutron detection.

Single-Crystal Perovskite Solar Cells Exhibit Close to Half A Millimeter Electron-Diffusion Length.

Single-crystal halide perovskites exhibit photogenerated-carriers of high mobility and long lifetime, making them excellent candidates for applications demanding thick semiconductors, such as ionizing radiation detectors, nuclear batteries, and concentrated photovoltaics. However, charge collection depreciates with increasing thickness; therefore, tens to hundreds of volts of external bias is required to extract charges from a thick perovskite layer, leading to a considerable amount of dark current and fast degradation of perovskite absorbers. However, extending the carrier-diffusion length can mitigate many of the anticipated issues preventing the practical utilization of perovskites in the abovementioned applications. Here, single-crystal perovskite solar cells that are up to 400 times thicker than state-of-the-art perovskite polycrystalline films are fabricated, yet retain high charge-collection efficiency in the absence of an external bias. Cells with thicknesses of 110, 214, and 290µm display power conversion efficiencies (PCEs) of 20.0, 18.4, and 14.7%, respectively. The remarkable persistence of high PCEs, despite the increase in thickness, is a result of a long electron-diffusion length in those cells, which wasestimated, from the thickness-dependent short-circuit current, to be ≈0.45mm under 1 sun illumination. These results pave the way for adapting perovskite devices to optoelectronic applications in which a thick active layer is essential.

Simulation Study of High-Speed Ge Photodetector Dark and Light Current Degradation

The reliability of Ge photodetectors used in the framework of Si photonics is studied using TCAD simulation, in order to better understand the physical origin of dark current and responsivity degradation observed in Sy <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">et al.</i> (2019). It is shown that bulk and interface recombination mainly modify the SRH dominated dark and light currents, while fixed charge and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{D}_{\mathrm{ it}}$ </tex-math></inline-formula> strongly impacts band-to-band tunneling dark currents. This essential distinction shows the necessity to discriminate the dominating transport mechanisms in photodetectors using activation energy measurement, in order to better identify the origin of performance degradation. It also strengthens the requirement for adequate passivation of all interfaces to reach higher lifetime of photodetectors.

Probing Dark Current Random Telegraph Signal in a Small Pitch Vertically Pinned Photodiode CMOS Image Sensor After Proton Irradiation

The dark current degradation and dark current random telegraph signal (DC-RTS) after proton irradiation are studied in new scale silicon microvolumes by using a commercial CMOS image sensor. Results show that previously reported empirical models describing the displacement damage-induced degradations are still valid despite the 10–100 times smaller depletion volume used. In addition, no evidence of significant total ionizing dose effects is observed. Finally, the reduction of the fraction of RTS pixels detected and the fraction of multilevel RTS pixels is directly linked to the reduction in pixel volume.

Statistical spread on the displacement damage degradation of irradiated semiconductors

Non Ionizing Energy Loss (NIEL) is the metric conventionally used to scale displacement damage degradation of irradiated semiconductor materials. Degradation of many electrical parameters is scaled according to this average parameter. But some deviations from NIEL scaling approach are observed from time to time. The stochastic nature of irradiation is often ignored. But, the degradation is not necessarily proportional to the average degradation level given by NIEL. The scatter of the irradiation degradation level is studied in this paper. This analysis provides some hints in order to interpret some discrepancies observed between measurements and predictions made with NIEL. Reliability of NIEL scaling method, applied to dark current degradation, is discussed for Silicon and Gallium Arsenide optoelectronic devices.

Electrical and optical characterisation of low temperature grown InGaAs for photodiode applications

Dilute bismide and nitride alloys are promising semiconductors for bandgap engineering, opening additional design freedom for devices such as infrared photodiodes. Low growth temperatures are required to incorporate bismuth or nitrogen into III–V semiconductors. However, the effects of low growth temperature on dark current and responsivity are not well understood. In this work, a set of InGaAs p-i-n wafers were grown at a constant temperature of 250, 300, 400 and 500 °C for all p, i and n layers. A second set of wafers was grown where the p and n layers were grown at 500 °C while the i-layers were grown at 250, 300 and 400 °C. Photodiodes were fabricated from all seven wafers. When constant growth temperature was employed (for all p, i and n layers), we observed that photodiodes grown at 500 °C show dark current density at −1 V that is six orders of magnitude lower while the responsivity at an illumination wavelength of 1520 nm is 4.5 times higher than those from photodiodes grown at 250 °C. Results from the second set of wafers suggest that performance degradation can be recovered by growing the p and n layers at high temperature. For instance, comparing photodiodes with i-layers grown at 250 °C, photodiodes showed dark current density at −1 V that is five orders of magnitude lower when the p and n layers were grown at 500 °C. Postgrowth annealing, at 595 °C for 15 min, on the two wafers grown at 250 and 300 °C showed recovery of diode responsivity but no significant improvement in the dark current. Our work suggests that growth of the cap layer at high temperature is necessary to maintain the responsivity and minimise the dark current degradation, offering a pathway to developing novel photodiode materials that necessitate low growth temperatures. The data reported in this paper is available from the ORDA digital repository (DOI: 10.15131/shef.data.12562346.v1).

CMOS Image Sensors and Plasma Processes: How PMD Nitride Charging Acts on the Dark Current.

Plasma processes are known to be prone to inducing damage by charging effects. For CMOS image sensors, this can lead to dark current degradation both in value and uniformity. An in-depth analysis, motivated by the different degrading behavior of two different plasma processes, has been performed in order to determine the degradation mechanisms associated with one plasma process. It is based on in situ plasma-induced charge characterization techniques for various dielectric stack structures (dielectric nature and stack configuration). A degradation mechanism is proposed, highlighting the role of ultraviolet (UV) light from the plasma in creating an electron hole which induces positive charges in the nitride layer at the wafer center, and negative ones at the edge. The trapped charges de-passivate the SiO2/Si interface by inducing a depleted interface above the photodiode, thus emphasizing the generation of dark current. A good correlation between the spatial distribution of the total charges and the value of dark current has been observed.

γ辐照导致中波碲镉汞光伏器件暗电流退化的机理研究

γ辐照导致中波碲镉汞光伏器件暗电流退化的机理研究

Dark-current estimation method for CMOS APS sensors in mixed radiation environment

CMOS active pixel sensors (APS) suffer from serious dark-current degradation when they are exposed in radiation environment. Considering the general situation that there are multiple kinds of energetic particles in radiation environment, a dark-current estimation method for pixel sensors due to mixed radiation particles is proposed in this paper. Based on the radiation effects induced by particles of all kinds, the dark-current amplitudes distribution among the pixels can be predicted through probabilistic analysis. Validation is implemented upon the radiation dark-image data of CMOS APS devices, which shows that the predicted dark-current distribution matches very well with the experimental data, and the difference is no more than 15%.

Total ionizing dose effects in pinned photodiode complementary metal-oxide-semiconductor transistor active pixel sensor**Project supported by the National Natural Science Foundation of China (Grant No. 11675259) and the West Light Foundation of the Chinese Academy of Sciences (Grant Nos. 2016-QNXZ-B-8 and 2016-QNXZ-B-2).

A pinned photodiode complementary metal–oxide–semiconductor transistor (CMOS) active pixel sensor is exposed to 60Co to evaluate the performance for space applications. The sample is irradiated with a dose rate of 50 rad (SiO2)/s and a total dose of 100 krad (SiO2), and the photodiode is kept unbiased. The degradation of dark current, full well capacity, and quantum efficiency induced by the total ionizing dose damage effect are investigated. It is found that the dark current increases mainly from the shallow trench isolation (STI) surrounding the pinned photodiode. Further results suggests that the decreasing of full well capacity due to the increase in the density, is induced by the total ionizing dose (TID) effect, of the trap interface, which also leads to the degradation of quantum efficiency at shorter wavelengths.

P-type BSI Image Sensor with Active Deep Trench Interface Passivation for Radiation-hardened Imaging Systems

We propose a P-type back-side-illuminated (BSI) image sensor for applications involving harsh ionizing environment. Its pixel structure implements a hole-collection vertical photodiode and 2T PMOS shared-readout circuitry. It also integrates capacitive deep trench isolation (CDTI) which allows active surface passivation. The proposed pixel structure exhibits intrinsically lower level of dark current than its N-type counterpart and improved radiation hardness. After receiving a total ionizing dose up to 1 kGy from 6 MeV gamma radiation, the average dark current of the P-type CDTI sensor increases only by a factor 3.6 compared with a 30-fold increase for the N-type counterpart. The proposed P-type exhibits much more effective surface passivation, which prevents dark current degradation due to surface thermal generation mechanism.

Radiation Effects in CCD on CMOS Devices: First Analysis of TID and DDD Effects

As CMOS image sensors become more and more attractive and with high performances, it becomes possible to use CCD on CMOS devices with reasonable lengths. However, no study has been done on the radiation hardness of such CCD on CMOS devices. Therefore, we propose in this paper a first study of Charge Transfer Inefficiency (CTI) and dark current degradation under TID and DDD irradiations. To do so, test chips have been processed in conventional deep submicron CMOS imaging technologies, and characterized before and after irradiations.

Design of Extremely Proximity Gettering Using Hydrogen Ion Implantation for Si CMOS Image-Sensor

As the pixel size in CMOS image-sensor has scaled down less than 1 μm, photo sensitivity which is a ratio of photo and dark current has been important. To improve photo sensitivity in CMOS image-sensor, the achievement of lower dark current is essential. Leakage current is influenced by crystallographic, trapped charge at the SiO2/Si interface, structural defects, and especially metallic contaminant impurities. Also, these contaminant impurities degrade the minority-carrier recombination lifetime. Thus, we investigated the dependency of the properties of CMOS image-sensor on metallic contamination. Standard aqueous solutions of metallic ion were dropped on the surface of silicon wafers and the wafers were spin dry. They were heated to drive the metallic ion contaminants into the silicon bulk. After that, we fabricated 4-Tr CMOS image-sensor cells. In silicon bulk wafer, the minority-carrier recombination lifetime decreased with increasing a metallic contaminant concentration. These contaminations result in degradation of dark current, sensitivity of photodiode and sensing margin of CMOS image-sensor. These results indicate that metallic contaminants are critical for increasing dark current because metallic contaminants remain inside the photo-diode region, ~3 μm. In our study, we applied a proximity relaxation-type gettering method. We formed the nano-cavities close to the depletion region using hydrogen ion implantation, as shown in Fig 1. These cavities getter metallic impurities on the cavities wall. Sensing margin of CMOS image-sensor implanted by hydrogen ion was dramatically improved, as shown in Fig 2. In addition, although metallic contaminant concentration increased, the device performances of CMOS image-sensor were constant compare with that of bulk wafer which were not implanted (Fig. 3). These results indicates that proximity gettering by using hydrogen ion implantation was effective in metal gettering for image-sensor. We investigated the correlation of metallic contaminant and sensing margin of CMOS image-sensor. Finally, we will suggest an extremely proximity gettering method for removing metallic contaminants of CMOS image-sensor.* This work was financially supported by the Brain Korea 21 Plus Program in 2013 and SiWEDS (Silicon Wafer Engineering and Defect Science).

Gamma and Proton-Induced Dark Current Degradation of 5T CMOS Pinned Photodiode $0.18~\mu\hbox{m}$ CMOS Image Sensors

The radiation tolerance of a 0.18 μm technology CMOS commercial image sensor has been evaluated with Co60 and proton irradiations. The effects of protons on the hot pixels and dynamic bias and duty cycle conditions during gamma irradiations are studied.

Rad Tolerant CMOS Image Sensor Based on Hole Collection 4T Pixel Pinned Photodiode

1.4μm pixel pitch CMOS Image sensors based on hole collection pinned photodiode (HPD) have been irradiated with <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60</sup> Co source. The HPD sensors exhibit much lower dark current degradation than equivalent commercial sensors using an Electron collection Pinned Photodiode (EPD). This hardness improvement is mainly attributed to carrier accumulation near the interfaces induced by the generated positive charges in dielectrics. The pre-eminence of this image sensor based on hole collection pinned photodiode architectures in ionizing environments is demonstrated.

Natural lithography nano-sphere texturing as antireflective layer on InP-based pin photodiodes

An antireflection coating was created for InP-based pin photodiodes using natural lithography with 100 nm-diameter SiO2 spheres. The surface showed a normal-incidence reflection of &lt;5% for wavelengths from 900 to 2500 nm. Photodiodes with surface texturing showed an enhancement in quantum efficiency with no dark current degradation.