Characterization of Single-Photon Avalanche Diode arrays in 150nm CMOS technology

Xu, Hesong; Braga, Leo H. C.; Stoppa, David; Pancheri, Lucio

doi:10.1109/aisem.2015.7066818

Cited by 7 publications

(5 citation statements)

References 11 publications

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“…The aim of this normalization is to exclude absolute values of quantities that are process and material dependent, such as thermal generation inside the depletion regions that cause dark count rate. Furthermore, dark count rates of modern SPAD arrays vary a lot, from 100 Hz (Leitner et al 2013) to a few hundred kHz (Xu et al 2008) and 1 MHz (Rosado and Hidalgo 2015), and it is difficult to accurately calibrate the thermal generation of carriers in the simulator. Therefore, the results show indirect optical crosstalk reduction relative to the 50Àlm-thick array without the crosstalk-reduction layer.…”

Section: Resultsmentioning

confidence: 99%

Indirect optical crosstalk reduction by highly-doped backside layer in single-photon avalanche diode arrays

et al. 2018

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A method of reducing indirect optical crosstalk in single-photon avalanche diode arrays is investigated by TCAD simulations. The reduction is accomplished by taking advantage of an enhanced optical absorption in a highly-doped Si layer on the backside of the wafer. A simulation environment was developed to give information about optical crosstalk by incorporating the experimental optical constants of the materials constituting the crosstalk-reduction layer. It is shown that the indirect optical crosstalk is greatly reduced by increasing the thickness and doping of the layer. A crosstalk reduction of 5 orders of magnitude is gained with addition of 1-μm-thick PureB=a-Si stack for the array processed on a p-type substrate, while the same reduction is achieved with a 1-μm-thick highly-doped Si layer (As, 1:1 Â 10 20 cm À3 ) for an array processed on an n-type substrate. Keywords Single-photon avalanche diode (SPAD) • SPAD array • Indirect optical crosstalk • PureBThis article is part of the Topical Collection on Numerical Simulation of Optoelectronic Devices, NUSOD' 17.

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Section: Resultsmentioning

confidence: 99%

Indirect optical crosstalk reduction by highly-doped backside layer in single-photon avalanche diode arrays

et al. 2018

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“…As mentioned in the Introduction, there have been studies on the crosstalk characterization of SPADs, e.g., the important contribution of indirect optical paths [13,14], the dependence of CMOS SPAD optical crosstalk on excess voltage, the distance between devices and die thickness [18], and the effect of the guard-ring width and p-n junction (multiplication region) depth on the crosstalk probability [25,26]. However, few of these reports address the timing correlation of crosstalk events in CMOS arrays.…”

Section: Discussionmentioning

confidence: 99%

“…The most obvious solution for minimizing the crosstalk is increasing the distance between devices, which significantly reduces the fill factor [25,26]. Another proposed solution for the crosstalk problem is the fabrication of deep isolating trenches (coated with metal [9, 27] or thick heavily doped deep diffusion regions [13,14]) to avoid direct optical and electrical crosstalk (although this solution is still not prone to indirect optical paths).…”

Section: Discussionmentioning

confidence: 99%

Timing and probability of crosstalk in a dense CMOS SPAD array in pulsed TOF applications

Jahromi

Kostamovaara

2018

Opt. Express

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As the distance between neighboring devices in large CMOS single-photon avalanche diode (SPAD) arrays is reduced for improving the density, increased crosstalk becomes an important issue, limiting the maximum practical fill factor of the array. In this study, the temporal correlation of crosstalk events, as well as the crosstalk probability, and their dependence on parameters, such as the illumination wavelength and intensity, and the distance between SPADs, are investigated via measurement of a ~45%-fill factor CMOS SPAD array fabricated using 0.35-µm high-voltage CMOS technology. The SPADs have 24 µm × 24 µm square-shaped active areas, and all devices share a common deep-N-well cathode. On-chip time-to-digital converters with 65-ps resolution are used to measure the timing of crosstalk events in "coincidence measurements." For the crosstalk measurements, the internal noise in one SPAD is used to produce crosstalk events in the neighboring devices. The measurement results indicate both optical and electrical crosstalk with the crosstalk events, having a specific temporal distribution. The crosstalk probability in the first two adjacent pixels is found to be 0.3% and 0.01%, with a distribution having full widths at half maximum (FWHMs) of 700 and 400 ps, respectively. In pulsed time-of-flight measurements, when one SPAD is triggered with external short-pulsed (FWHM of approximately 200 ps) illumination, extra correlated noise in the adjacent SPADs added to the crosstalk noise, increasing the correlated noise considerably. This additional noise was a secondary effect of the absorbed laser photons deep in the substrate.

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“…Each measurement cycle with our hyperspectral single photon lidar produces a data frame

that contains 32 × 32 delay counter values (in this study, only 30 spectral channels are used among the 32 channels available) representing the time-of-flight time differences

between the supercontinuum laser triggering time at

and the return pulse detection time at

as:

where i and j denote the pixel indices in the intensity and wavelength directions, respectively, and k denotes the location of the frame in a sequence of measurements. The pixels are triggered either by photons originating from the target return pulse or ambient illumination source, or alternatively by SPAD array intrinsic noise, such as dark current noise [ 54 ], afterpulsing [ 65 ], or crosstalk [ 66 , 67 , 68 , 69 ]. The pixels in the SPAD array that have not triggered during the measurement cycle are denoted by value

.…”

Section: Methodsmentioning

confidence: 99%

Feasibility of Hyperspectral Single Photon Lidar for Robust Autonomous Vehicle Perception

Taher

Hakala

Jaakkola

et al. 2022

Sensors

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Autonomous vehicle perception systems typically rely on single-wavelength lidar sensors to obtain three-dimensional information about the road environment. In contrast to cameras, lidars are unaffected by challenging illumination conditions, such as low light during night-time and various bidirectional effects changing the return reflectance. However, as many commercial lidars operate on a monochromatic basis, the ability to distinguish objects based on material spectral properties is limited. In this work, we describe the prototype hardware for a hyperspectral single photon lidar and demonstrate the feasibility of its use in an autonomous-driving-related object classification task. We also introduce a simple statistical model for estimating the reflectance measurement accuracy of single photon sensitive lidar devices. The single photon receiver frame was used to receive 30 12.3 nm spectral channels in the spectral band 1200–1570 nm, with a maximum channel-wise intensity of 32 photons. A varying number of frames were used to accumulate the signal photon count. Multiple objects covering 10 different categories of road environment, such as car, dry asphalt, gravel road, snowy asphalt, wet asphalt, wall, granite, grass, moss, and spruce tree, were included in the experiments. We test the influence of the number of spectral channels and the number of frames on the classification accuracy with random forest classifier and find that the spectral information increases the classification accuracy in the high-photon flux regime from 50% to 94% with 2 channels and 30 channels, respectively. In the low-photon flux regime, the classification accuracy increases from 30% to 38% with 2 channels and 6 channels, respectively. Additionally, we visualize the data with the t-SNE algorithm and show that the photon shot noise in the single photon sensitive hyperspectral data contributes the most to the separability of material specific spectral signatures. The results of this study provide support for the use of hyperspectral single photon lidar data on more advanced object detection and classification methods, and motivates the development of advanced single photon sensitive hyperspectral lidar devices for use in autonomous vehicles and in robotics.

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Characterization of Single-Photon Avalanche Diode arrays in 150nm CMOS technology

Cited by 7 publications

References 11 publications

Indirect optical crosstalk reduction by highly-doped backside layer in single-photon avalanche diode arrays

Indirect optical crosstalk reduction by highly-doped backside layer in single-photon avalanche diode arrays

Timing and probability of crosstalk in a dense CMOS SPAD array in pulsed TOF applications

Feasibility of Hyperspectral Single Photon Lidar for Robust Autonomous Vehicle Perception

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