Si PIN Research Articles

Electrostatic Force-Assisted Transfer of Flexible Silicon Photodetector Focal Plane Arrays for Image Sensors.

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 × 1012 Jones at an applied voltage of -3 V at 940 nm.

Design of a metasurface deflector for guided absorption enhancement in a Si PIN photodiode

We numerically demonstrated a surface-illuminated Si PIN photodiode (PD) structure with a metasurface composed of etched isosceles triangle pillars that can enhance sensitivity in the near-infrared wavelength range (NIR) by enabling directional scattering (DS) of photons. The metasurface is designed to act as a deflector to increase the absorption efficiency by extending the photon dwell time. This is particularly effective in thin intrinsic layers (i-layers) of silicon, surpassing the capabilities of conventional omnidirectional scattering gratings. Our results show a 3.5-fold increase in internal quantum efficiency over wavelengths above 0.9 µm compared to the structure without metasurface. The absorption enhancement brought about by directional scattering is not limited to thin i-layers; it can potentially improve a wide range of photodiode geometries and structures. Furthermore, the proposed structure, consisting of an all-Si layer and a simple geometric etching process, makes it compatible with foundry fabrication methods and opens up new possibilities for expanding applications of Si PDs.

Thermal, X-ray spectroscopy, morphological, density functional theory and molecular modeling studies on yttrium(III), germanium(IV), tungsten(VI), and silicon penicillinate antibiotic complexes

This manuscript elucidates the thermal stability analysis of four distinct penicillinate complexes, comprising yttrium(III), germanium(IV), tungsten(VI), and silicon, over a temperature ranging from 25 to 800°C. Thermal data revealed the high thermal stability nature of the decomposition steps. According to the spectroscopic measurements, the chemical formula of penicillinate complexes were [Y(Pin)2].Cl.6H2O complex (1), [Ge(Pin)2].2Cl.2H2O complex (2), [W(Pin)2].4Cl complex (3), and [Si(Pin)2].2Cl.2H2O complex (4). The powder XRD pattern revealed crystalline to polycrystalline natures. The synthesized penicillinate complexes were subjected to theoretical calculations utilizing density functional theory (DFT) calculations, employing the lanL2DZ/6-311G++ level of theory. The optimized geometry of each penicillinate complex was discerned, and a comprehensive evaluation of various properties, including the HOMO→LUMO electronic energy gap, molecular electrostatic potential map, and additional physical parameters, was conducted and validated against experimental findings. Molecular docking tool was used to explore the anticancer activity of the synthesized penicillinate complexes in comparison with penicillin potassium drug (Pin). For the computational investigation, two kinases — CSF1R (PDB ID: 7MFC) and MEK2 (PDB ID: 1S9I) associated with breast cancer progression and estrogen-dependent breast cancer were utilized. This comprehensive analysis provides a deeper understanding of the synthesized penicillinate complexes and their potential applications. KEY WORDS: Penicillinate complexes, TGA-DrTGA, TEM, XRD, DFT/TD-DFT, Molecular docking Bull. Chem. Soc. Ethiop. 2024, 38(4), 973-988. DOI: https://dx.doi.org/10.4314/bcse.v38i4.13

Heterogeneous Integration for High Performance Electronic and Photonic Devices

In this paper, two representative heterogeneous integrated applications with great performance based on epitaxial layer transfer process are reported. The SiC integrated Si PIN limiter has shown power handling capability of 150W (continues Wave) and 370W (long pulse) at 5.4GHz, which shows outstanding performance than conventional GaAs limiter. While the SiC integrated InP PIN photodetector has shown a high performance of 3-dB bandwidth over 67GHz, and 42% increasing of the optical responsibility over 0.51 A/W compared to the traditional PD. The results verified great potential of transistor level heterogeneous integration for high performance electronic and photonic devices.

New Crystal Photodiode Combination for Environmental Radiation Measurement

Here, a new design will be introduced to detect radiation in the environment with high efficiency. The designed structure consists of placing ZnS–Si APD and PIN photodiodes at the ends of conventional crystals such as NaI(Tl) and CsI(Tl). Since ZnS is transparent to photons with wavelengths between 340 and 10000 nm, photons coming from the crystals are absorbed directly in the depletion region and generate primary particles. With an increase in the number of generated primary particles, a stronger and cleaner signal is obtained. In the simulation work, the light generated by 30 keV–3 MeV gamma rays in the crystals was obtained using the Geant4 simulation code. The single-particle Monte Carlo technique was used to calculate the photodiode output signal for the crystal emission spectrum. The simulation results showed that the crystals and ZnS–Si photodiode structures formed a good combination. The high quantum efficiency and low excess noise factor make the ZnS–Si structure an excellent choice for scintillating light detection.

Total kinetic energy release in the fast neutron induced fission of actinide nuclei

The total kinetic energy release and fission mass distributions for the fast neutron (En = 3–100 MeV) induced fission of 232Th, 233U, 235U, 237Np, 239Pu, 240Pu, and 242Pu have been measured using the LANSCE facility. The neutron energies were deduced from time-of- flight measurements. The fission fragments were detected using Si PIN diode detectors, giving us the fragment energies. The actinide targets were made by vapor deposition leading to high-quality targets, that were thin and uniform with reduced impurities. Corrections were made to the data for pulse height defect and the fragment energy loss in the target and its backing. The TKE distributions were Gaussian in shape and their mean value as a function of incoming neutron energy could be fitted with second order polynomials. In the case of 233U and 235U, our measurements agree with prior work. Our measurements for 232Th are unique. Our data agree with Viola scaling. The constant position of the heavy mass peak is interpreted as being due to the influence of the N = 88 and Z = 50 shells. The GEF model predictions agree with the data in general as do the CGMF model predictions.

Effect of reverse voltage on alpha spectra of pre-conditioned Si PIN diodes deployed in vacuum/ambient environment

Semiconductor-based Si PIN diodes are employed for radiation detection owing to their many advantages. However, their performance and reliability heavily rely on their pre-conditioning and the environment in which they are deployed. In this article, the response of Si PIN diodes that are subjected to two different pre-conditions [heat-treated at 100 °C (HT) and exposed to 85% relative humidity (HUM)] and two deployment environments [vacuum and ambient] to alpha particles emanating from triple-alpha source (239Pu-5155 keV, 241Am-5486 keV, and 244Cm-5805 keV) are investigated. Prior to alpha spectroscopy measurements, a meticulous electrical characterization, in terms of reverse current-voltage (IR-VR) and reverse capacitance-voltage (CR-VR) measurements are carried out. The IR-VR characteristics revealed that the leakage current (IR) is higher for measurements performed in ambient as compared to vacuum, while CR-VR characteristics are utilized to set the minimum reverse voltage (VR) that resulted in depletion width commensurate with the range of alpha particles. In order to confirm the optimum VR for maximum charge collection, alpha spectra are obtained in vacuum conditions for different values of VR ranging from 0 to 48.6 V, which showed a left-exponential Gaussian convoluted lineshape. A systematic analysis of the lineshape in terms of the fitting parameters viz, peak position, FWHM, area under the peak, and tailing parameter, revealed that the most robust data is obtained at an optimum VR of 4.6 V, where saturation is observed in peak position, area under the peak and tailing parameter. It is to be added that in the present experiment, 4.6 V is the optimum VR for obtaining robust measurements even for pre-conditioned diodes in different deployment conditions and is thus suitable for field condition measurements.

On-chip lateral Si:Te PIN photodiodes for room-temperature detection in the telecom optical wavelength bands.

Photonic integrated circuits require photodetectors that operate at room temperature with sensitivity at telecom wavelengths and are suitable for integration with planar complementary-metal-oxide-semiconductor (CMOS) technology. Silicon hyperdoped with deep-level impurities is a promising material for silicon infrared detectors because of its strong room-temperature photoresponse in the short-wavelength infrared region caused by the creation of an impurity band within the silicon band gap. In this work, we present the first experimental demonstration of lateral Te-hyperdoped Si PIN photodetectors operating at room temperature in the optical telecom bands. We provide a detailed description of the fabrication process, working principle, and performance of the photodiodes, including their key figure of merits. Our results are promising for the integration of active and passive photonic elements on a single Si chip, leveraging the advantages of planar CMOS technology.

Segmented silicon-based solid-state detector with thin dead layer for superheavy element research

Silicon-based solid-state detectors (SSDs) are crucial for investigating the properties of superheavy elements (SHEs), since they measure the energy of SHEs and charged particles that are emitted as successive decay events of the SHEs. We have developed a segmented SSD for SHE studies using the new gas-filled recoil ion separators (GARIS-II and GARIS-III) at RIKEN. It is based on a back-illuminated Si PIN photodiode in which the irradiation is through the N+ layer. The detector is introduced as a side one for the GARIS focal plane detection system. To investigate the characteristics of the SSD, 241Am α particles were irradiated by automatically moving and rotating the α source for each segmented portion of the SSD. A Monte Carlo simulation was also performed to estimate the dead layer thickness of the segmented SSD.

Effect of pre-adsorbed moisture and humidity on I–V characteristics of Si PIN diode

Effect of pre-adsorbed moisture and humidity on I–V characteristics of Si PIN diode

Thermal drift reduction in photodiode dosimeters with switching bias

The effect of temperature on dosimetric measurements is a major limitation of solid-state dosimeters. This is especially true for PIN photodiode dosimeters, where the dark current depends exponentially on temperature. To minimize this effect, a compensation method is presented that relies on the diode structure itself without the need for an external sensor or device. During irradiation, the photodiode is periodically switched from reverse to forward polarization to determine the temperature of the device. This measurement is based on the linear dependence between the temperature and the forward voltage of the diode when it is operated at constant current. An electronic circuit implementing this procedure was developed and used for experimental characterization of the response to radiation of the BPW34S Si PIN photodiode. The proposed procedure reduced the uncertainty due to thermal drift by a factor of 7.5. In addition, an average dose rate sensitivity of 12 ± 2 nC/cGy was measured, with a sensitivity degradation below 2% for the irradiation cycle of 21.4 Gy performed under a 6 MV photon beam. We have shown that a p-n junction can be successfully used to compensate for the temperature effect on the dosimetric measurement.

SUNSTORM 1/X-ray Flux Monitor for CubeSats (XFM-CS): Instrument characterization and first results

SUNSTORM 1 CubeSat was launched to Sun-synchronous low Earth orbit on August 17 2021. The primary purpose of the mission is an in-orbit demonstration of X-ray Flux Monitor (XFM) instrument. XFM is an innovative solar X-ray spectrometer for measuring and characterizing solar flares, which are known to be linked to a variety of space weather phenomena. XFM represents a next generation of solar X-ray flux monitors. It is based on silicon drift detector technology, which provides several notable performance improvements over its predecessors, which are based on Si PIN detectors. Transversal electric field and lower output capacitance allow operation at much faster pulse processing shaping times, allowing the system to achieve about 10 times higher throughput without saturation while also making it less sensitive to the increase of leakage current due to high temperature and/or radiation damage. Thus, XFM instruments can cover a very wide dynamic range of solar X-ray emission from the most quiescent conditions to the strongest X-class solar flares, while maintaining good spectral resolution (<200 eV at 6 keV). The instruments are thus well suited for both X-ray flux monitoring and spectroscopic studies of the solar corona.In this paper we describe the ground characterization and evaluation of the scientific performance of the first operational XFM instrument, a CubeSat version XFM-CS on-board SUNSTORM 1, which is a satellite built in the framework of the FLY element of ESA’s General Support Technology Programme, dedicated to the early space testing of promising new technologies. We also provide an analysis of the first results obtained during the in-orbit commissioning and early operations of SUNSTORM 1. We show the comparison of the observed scientific performance of XFM-CS with the expected performance based on theoretical modeling and ground calibration results. Finally, we describe the cross calibration of the X-ray flux data from XFM-CS with the new GOES-R series GOES X-ray sensors.

Commercial photodiodes and phototransistors as dosimeters of photon beams for radiotherapy.

The response to radiation typically used in radiotherapy treatments has been experimentally evaluated for three samples of two phototransistors (BPW85B and OP505A) and two PIN photodiodes types (VTB8440BH and BPW34S). To that end, a staggered irradiation cycle has been applied which included dose rate values from 0.81 to 4.87cGy/s, achieving a total absorbed dose of 21.4Gy. The samples have been irradiated with a linear accelerator and the relations between the induced photocurrent and the average and instantaneous dose rates, and between the accumulated charge and the absorbed dose, have been determined. The radiation-induced output currents were measured by means of an external interface of the devices to a previously designed readout unit. Experimental results of Si PIN photodiode BPW34S have shown a sensitivity of (13.9±0.5) nC/cGy, slight sensitivity dependence on dose rate, and a high linearity of the current with the average and instantaneous dose rate, requiring only 10V of reverse bias voltage. This device thermal drift has characterized and modeled for temperature effect compensation. Silicon PIN photodiode BPW34S, previously tested for X-rays and Co-60 gamma ray source, can also be a reliable candidate for dose rate and absorbed skin dose determination in typical radiotherapy treatments irradiations. A low sensitivity loss below 2% up to 21.4Gy has been measured, allowing its use as an affordable reusable skin dosimeter. Moreover, no significant difference has been observed between its response to dose-per-pulse and changing pulse repetition frequency in terms of sensitivity and dependence with dose-rate value.

Building a VME spectrometer and testing Si PIN diode detector: a feasibility study for the first nuclear astrophysical experiments using a pelletron

This work presents the logical design, connections between NIM and VME elec­tronic modules, and the data acquisition programming to build a complete detector readout system. The test experiments were carried out with commercial silicon PIN diode S3590-09 bare detectors bombarded by charged particles from a 241Am α-source and Rutherford elastic backscattering (RBS) protons induced by 2.5 MeV proton beam bombarding on an Au-on-glass target, and with a NaI scintillation detector bombarded by gammas from 27Al(p, γ)28Si reaction with proton beam energy of 1.379 MeV. The test showed that the spectrometer operated steadily and its versatility for different kind of detector. The energy resolutions of the Si diodes were less than 0.5% energy of a charged particle, which satisfies the foreseen requirement for the upcoming experiments.

Optimizations of Si PIN diode phase-shifter for controlling MZM quadrature bias point using SOI rib waveguide technology

Commercial high-speed silicon (Si) Mach-Zehnder modulator (MZM) required to be active around the quadrature bias point (linear transmission area) with low power consumption, small footprint, and small drive voltage. The bias controlling is done by an optical phase-shifter (PS). However, the accuracy is limited by the drive voltage, laser thermal drift, and fabrication errors. To overcome these problems, we propose in this paper the study and analysis of Si PIN diode PS under forward biasing at 1550 nm wavelength using the standard 220 nm substrate silicon-on-insulator (SOI) rib waveguide technology. Numerical investigations were carried out on the key geometrical parameters, doping concentration, doping locations, operating wavelength, biasing level. Results show that the optimal design can be operated with a lower voltage (Vπ = 1.629 v), lower attenuation (α = 28.985 dB/cm), and short device length with an extremely small voltage-length product VπL = 0.815 vmm. Thus, this PS can be used for designing an efficiency high-speed MZM and to obtain better performances in the optical commutation system.

Impact Energy and Angular Dependence of L X-ray Emission from a Thick Polycrystalline Tungsten Element Induced by 15–25 keV Electrons

The impact energy and angular dependence of L X-rays of a thick polycrystalline tungsten (W; atomic number, Z = 74) target induced by 15–25 keV electrons has been measured at different angles varying from 15° to 75° at intervals of 5° using a Si PIN photodiode detector. The variation of measured relative intensity of Ll, Lα, Lβ and Lγ characteristic lines as a function of incidence angle is found to be anisotropic and the measured variation compares well with the PENELOPE simulation results. The angular variation of intensity ratio of Ll/Lα and Lβ/Lα shows anisotropic distribution, whereas the angular variation of the Lγ/Lα ratio exhibits almost isotropic distribution within the uncertainty of measurements. These measured ratios are found to be in good agreement with Monte Carlo (MC) calculations. The measured intensity ratios of Lβ/Lα and Lγ/Lα at a given incidence angle show a linear dependence with impact energy and exhibit good agreement with simulation results; however, the measured intensity ratio of Ll/Lα shows a non-linear variation with the impact energy and yields poor agreement with theoretical calculations.

A portable, low-cost and sensor-based detector on sweetness and firmness grades of kiwifruit

During storage, the sweetness of kiwifruit increases and its firmness decreases quickly. Since the sweetness is linked to consumers’ taste preference, and the firmness is regarded as the primary indicator of kiwifruit eating ripeness, detecting the sweetness and firmness are welcome by kiwifruit sellers, consumers and processors. To make the detected results intuitive and acceptable to more people, this study aimed to present a portable, low-cost, sensor-based grade detector on sweetness and firmness of kiwifruit. The detector consisted of a control/processing unit, a LED panel and driver unit, a light signal detection and amplifier unit, an input/output unit and a battery. Micro-controller of STM32 was used to do data collection and processing. The LED panel with nine LEDs at peak wavelengths of 800, 810, 850, 880, 900, 940, 970, 1000 and 1100 nm were used as light source. The reflected light from the kiwifruit was sensed by a Si PIN photodiode. The software of the detector was programmed by using C language. Kiwifruit varieties of 'Xuxiang' and 'Huayou' were used as samples, and their sweetness and firmness were divided into four grades. The model of support vector machine was established to determine kiwifruit grades. The validation experiment showed that the identification accuracies of the grade detector were 82.0% for sweetness and 74.0% for firmness of ‘Xuxiang’ variety, and 85.5% and 91.5% for sweetness and firmness of ‘Huayou’ variety, respectively. The detection time for one sample was less than 3 s.

Comparative Numerical Analysis of the Robustness of Si and SiC PiN Diodes Against Cosmic Radiation-Induced Failure

This work aims at extending the predictive simulation technique for cosmic ray-induced failure analysis from Si PiN diodes [1] to SiC PiN diodes. Accurate 3D cylindrical-symmetric transient simulations were performed with a minimum mesh size of 20nm at the center track of the impinging ion and a maximum time step of 0.1ps during the development of the ion-induced transient current. We made a comparative study between a SiC PiN diode and a Si PiN diode with the same blocking voltage of 1.5kV, using the same heavy ion transportation models. In the simulation, we observed different ion-induced current transients, differing not only in the peak value of the current, but also in its duration. Due to different physical mechanisms, the dependence of the ion-induced current on the reverse pre-bias voltage and the numerical mesh adaptations are also different. Eventually, we brieflydiscuss electro-thermal simulations, which indicate once more that the ion-induced transient current in the SiC PiN diodes under consideration is primarily drift current and involves only negligible impact ionization.

Application of a Portable XRF Spectrometer for &amp;lt;i&amp;gt;In-Situ&amp;lt;/i&amp;gt; and Nondestructive Investigation of Pigments in Two 15th Century Icons

A simple portable X-Ray Fluorescence (XRF) spectrometer was successfully used for in-situ and nondestructive identification of the painting materials in two 15th century icons from the Onufri Museum in Beart, Albania. The spectrometer is based on a low power X-ray tube, a thermoelectrically cooled Si PIN detector and the spectrum acquisition system. It was assembled and adjusted at our laboratory for the investigation of the icons. A small number of pigments were clearly identified by X-Ray Fluorescence (XRF) measurements in both icons. This includes Lead white for the white color, gold and yellow ochre for the yellow color, red lead, cinnabar and red ochre for the red color, as well as cooper based pigments for the green color. At the same time, the investigation raised some new questions that need further investigations by the use of additional analytical techniques. The results show that in both icons are used similar pigments, which are in accordance with the Byzantine icon painting tradition.

Experimental evidence of molecular coherence effects in the bremsstrahlung radiation processes

The first experimental evidence of Young-type interferences is presented in bremsstrahlung (BS) processes by measuring the double differential cross sections (DDCS) of BS photons emitted from a two-centre N2 molecule under impact of 4.0 keV electrons. The spectra were recorded for emission of photons in the angular range of 45°–120° and the energy range of 2.0–3.8 keV using a Si PIN photodiode detector (FWHM = 165 eV at 5.9 keV). The measured variation of DDCS ratio of N2 to Ar as a function of photon energy shows no obvious signature of interference structure. However, the measured angular distribution of the intensity ratio of BS photons of N2 to Ar is found to exhibit the noticeable oscillations. Furthermore, a clear oscillatory structure is observed in the angular distribution of BS photons if the intensity of photons emitted from N2 molecules at angle θ to the intensity of photons emitted at angle 90°, i.e. I(θ)/I(90°) is plotted as a function of emission angle. Noting the fact that, only one theoretical work on coherence effects in BS processes under low-energy electron impact with homonuclear diatomic molecules is reported in the literature by Borie et al (1970 Phys. Rev. A 2 1443) which fails to explain the observed oscillations and shows orders of magnitude difference in the amplitude and mismatch in the shape of oscillations. The presence of observed oscillations is suggested to arise due to coherent superposition of BS photons of a given energy emitted in scattering of 4.0 keV electrons with a two-centre N2 molecule. Strong disagreement between our measurements and the calculations from Borie et al theory clearly suggests that a more refined and adequate theoretical model together with additional experimental investigations are needed to verify the present observations.