Silicon Technology Research Articles

From Laboratory to Production: Learning Models of Efficiency and Manufacturing Cost of Industrial Crystalline Silicon and Thin-Film Photovoltaic Technologies

Efficiency and manufacturing cost are two key elements for the photovoltaic (PV) industry. In this paper, we look at the time-dependent evolution of efficiency and manufacturing cost for PV devices. For efficiency improvements, the empirical model developed by Goetzberger et al. is applied to describe the time-dependent improvements for a concrete technology in laboratory cell's research and development, and the learning factor c is extracted. The application of the Goetzberger's model is extended to industrial PV modules. It is forecasted that cadmium telluride (CdTe) and copper gallium indium diselenide (CIGS) will have the average module efficiency in 2020 of 17.9% and 16.4%, respectively. Over 21.8% commercial module efficiency is projected with n-type Si interdigitated back contact technology, while average module efficiencies of 17.4%, 18.4%, and 19.4% are projected for conventional p-type multi-, mono-, and mono-passivated emitter and rear cell (PERC), respectively. For the manufacturing cost, we parameterized the learning curve model of manufacturing cost for industrial crystalline silicon (c-Si), CdTe, and CIGS technologies. As projected by the learning curve, the manufacturing cost of c-Si and thin-film modules may reach 0.2 $/Wp or below, when the cumulative production reach 1 TW. The learning rate for Si (24.2%) is greater than CdTe (19.1%) and CIGS (8.1%).

Doped silicon quantum dots as sources of coherent surface plasmons

In the present work, we propose using a doped silicon quantum dot (Si-QD) as a source of coherent surface plasmons (SPASER). The possibility of spasing in single Si-QD is investigated theoretically utilizing full quantum mechanical treatment. We show that spasing can take place in doped Si-QDs whenever the quality factor of a plasmon mode exceeds some minimum value. The minimum value depends on the size and doping concentration of Si-QDs. It can be used to design an optimum structure as SPASER in silicon technologies. The condition on the quality factor is translated to a condition for radius and it is shown that for a given localized surface plasmon (LSP) mode, the radius should be less than the critical value. This value only depends on the mode index. The required relations for design purposes are derived and, as an example of feasibility of the approach, a SPASER is designed for mid infrared. Moreover, we propose a more applicable device by arranging an array of doped Si-QDs on top of a graphene layer. Interaction between the surface plasmon polariton (SPP) modes of graphene and LSP modes of Si-QDs causes outcoupling of an intense ultra narrow beam of coherent SPPs to be used in real probable applications.

Three-Dimensional Transport Simulations and Modeling of Densely Packed CNTFETs

Carbon nanotube (CNT) field-effect transistor (FET) based applications require multiple CNTs with small tube pitches for competing with existing silicon technologies. The associated dense packing of CNTs leads to electrostatic interactions between the tubes also known as screening effects. In this paper, the impact of the latter on the CNT current and charge density has been investigated by means of three-dimensional (3D) device simulation (TCAD), in which the CNT is represented by its actual 3D structure rather than by a one-dimensional (1D) line, allowing to include the effects of an inhomogeneous charge and current density distribution along the CNT circumference. Different analytical models describing the impact of the oxide thickness, CNT diameter and CNT pitch on the oxide capacitance are compared. Using the most accurate model, the dependence of drain current, transconductance, subthreshold slope and transit frequency on the above mentioned parameters has been determined using TCAD simulations.

Hollow-Core-Integrated Optical Waveguides for Mid-IR Sensors

Integrated hollow-core antiresonant reflecting optical waveguides are designed and analyzed for mid-infrared propagation. With a proper selection of waveguide materials and geometry, low loss propagation lower than 1.5 dB/cm in the whole 2.5–14 μm range could be achieved. Single-mode waveguides, with a modal purity above 95% after propagation lengths of few millimeters, have been designed at 4 and 9 μm. The waveguides could be realized using fabrication and materials fully compatible with standard Silicon technology, enabling the chip-scale integration of Mid-IR devices for gas sensing applications.

Graphene/MoS2/Si Nanowires Schottky-NP Bipolar van der Waals Heterojunction for Ultrafast Photodetectors

Here, we demonstrate a novel 2-D–3-D graphene (Gr)/MoS2/Si nanowires Schottky-NP bipolar van der Waals heterostructure, which allows the combination of the unique properties of 2-D layered materials with the proven merits of well-developed silicon technologies. Significantly, the resultant devices exhibit an ultrahigh response speed of 17 ns with a broad spectral response characteristic, which represents most fast response for 2-D transition metal dichalcogenide (TMD)-based photodetectors and is comparable to that of commercial Si photodetectors. A high responsivity of 0.6 A $\text{W}^{-{1}}$ and a detectivity of ${8}\times {10}^{{12}}$ Jones are also achieved. This result suggests a pathway for the fabrication of high-speed photodetectors based on TMDs.

Broadband visible-to-telecom wavelength germanium quantum dot photodetectors

Germanium (Ge) quantum dot (QD) photodetectors (PDs) were fabricated on Ge substrates exhibiting a broadband, visible to near-infrared (near-IR) photoresponse in the λ = 400–1550 nm range. Room-temperature responsivities (Rsp) up to 1.12 A/W and internal quantum efficiency IQE = 313% were obtained, superior to conventional silicon and germanium photodiodes. Noise analysis was performed at visible λ = 640 nm and telecom λ = 1550 nm wavelengths, both yielding room-temperature specific detectivity D* ≃ 2 × 1010 cm Hz1/2 W−1. Lowering the operating temperature and incident power led to sharply enhanced performance, with D* = 1.1 × 1012 cm Hz1/2 W−1 and IQE = 1000% at T = 100 K for an incident power of 10 nW at λ = 1550 nm. Based on their simple fabrication and silicon technology compatibility, these Ge QD PDs represent a promising alternative for broadband, high-performance visible to near-IR detection.

Active-edge FBK-INFN-LPNHE thin n-on-p pixel sensors for the upgrade of the ATLAS Inner Tracker

In view of the LHC upgrade for the High Luminosity phase (HL-LHC), the ATLAS experiment plans to replace the Inner Detector with an all-silicon system. The n-on-p silicon technology is a promising candidate to achieve a large area instrumented with pixel sensors, since it is radiation hard and cost effective. The paper reports on the performance of thin 100 and 130 μ m n-in-p planar pixel sensors produced by FBK-CMM with active-edge technology in collaboration with LPNHE and INFN. Beam-test results are presented, with focus on the hit efficiency at the detector edge of a novel design consisting of a staggered deep trench.

Realization of all-optical NOT and XOR logic gates based on interference effect with high contrast ratio and ultra-compacted size

In this paper, an ultra-compact structure is presented for realization of all-optical NOT and XOR logic gates which can be compatible with silicon technology. Logic gates are based on two-dimensional photonic crystals, and the lattice constant and the radius of the rods are selected in such a way in order to operate the logic gates at 1550 nm. The proposed structure consists of three waveguides which are connected to each other using a T-shaped junction. This structure is optimized by two nano-resonators and has also two input ports and one output port. For our numerical studies, the plane-wave expansion and finite-difference time-domain methods have been used. The contrast ratios for the proposed all optical NOT and XOR logic gates are respectively 43.40 and 43.38 dB. The response time of the logic gates is 0.37 ps, which in turn creates a data transmission rate of 3.15 Tb/s. Our studies have shown that the NOT-designed logic gate is suitable for the use in optical integrated circuits.

Guest Editorial Special Issue on 2-D Materials for Electronic, Optoelectronic, and Sensor Devices

Silicon CMOS technology has fueled the phenomenal growth in semiconductor electronics over the past several decades. The miniaturization of a transistor, the basic tenet of technology scaling, is at the core of this revolution. Despite several challenges, the innovations in materials, processes, and device architecture have ensured that Moore’s law is still alive and going strong, with 7-nm silicon FinFET technology in volume production. However, over the past couple of decades, there has been a realization that the silicon CMOS technology may reach the end of scaling unless it is augmented and complemented by other semiconductors. For instance, there has been a substantial effort in the research community to integrate other bulk semiconductors such as germanium and III-Vs, into silicon technology.

A newly developed silicone technology to improve thermal performance of curtain walls

ABSTRACTArchitectural trends in modern commercial façades tend towards larger glass surfaces and slimmer frame designs like structural glazing, which result in increased transparency of the design. Design should however take into consideration energy efficiency requirements. Energy regulations and climate policy targets set up strict requirements for future buildings. According to the Energy Performance of Buildings Directive, by 2020 all new buildings in EU will have to be built as “Nearly Zero‐Energy Buildings”. All public buildings have to meet that target two years earlier, at the end of 2018. These targets dictate high demand on building envelope performance and pose challenges in building design. Respecting these targets brings along an increased comfort for the building's occupants: higher internal surface temperatures reduce condensation risk and prevent mould growth while improving the indoor climate. Current solutions reduce the energy loss of curtain walls by using insulating glass units, thermally broken framing systems, low‐emission coatings and warm edge spacers. However, these technologies are reaching their maximal efficiency as they have been on the market for several decades, hence new materials and technologies are required. Since all the major elements of the façade have already been optimized, it becomes critical to ensure that the design of details is not neglected. There is a strong relationship between material characteristics at the detail level and the resulting impact on performance and durability of a façade. Unfortunately, further energy optimization of curtain walls often comes at a price, since the obtained performance improvements are limited whilst adding significant complexity and costs. The challenge today is therefore to develop solutions providing a better performance at a reasonable cost and low complexity to ensure easy adoption of the market and consequently, a significant impact on the improvement of the building stock. This paper introduces a brand‐new silicone technology and illustrates design integration and performance within different structurally glazed façade systems such as unitized and toggle designs. Looking at façades requiring curtain wall U‐values (UCW) below 1.2 W/m2K, the improvements in terms of surface temperatures, psi‐value, but also overall Ucw‐value can be remarkable at efficient cost. A comparison to existing conventional technologies is shown with regards to the overall level of impact on the entire curtain wall energy efficiency performance.

Experimental study of dust impact on power output degradation of various photovoltaic technologies deployed in West Timor, Indonesia

Photovoltaic (PV) technology has been widely used as a source of electricity for household appliances, electrical vehicles, industrial and commercial systems. Energy yield by a PV panel installed in the field is dependent on the amount of photon reaching its solar cells. One environmental factor playing an important role to reduce PV power production is dust. Dust particles generated by human work and natural processes reflect, absorb and scatter solar radiation. This research examined dust effect on power degradation of several PV technologies commonly found in West Timor islands including mono-crystalline silicon (mc-Si), amorphous silicon (a-Si), and polycrystalline silicon (pc-Si) technology. Dust collected from a PV power plant in the island was coated artificially onto the front side of the PV samples. Furthermore, electrical parameters of the panels were examined using a SPIRE 5600SLP solar simulator. A HP spectrophotometer was applied to measure optical property of the dust. Results revealed that maximum power output value of all modules decreased as dust concentration increased. There is a linear relationship between PV output degradation and dust density <0.3 mg/cm2. This is in line with the dust transmittance value which is linear within the density <0.3 mg/cm2. In addition, it was found that different PV technologies shared different respond to the power output reduction. According to the results, at the same density of dust collected from the site in West Timor, a-Si PV module exhibited the largest maximum power output degradation followed by pc-Si and mc-Si technology.

Optimized Adhesive for Structural Sealant Glazing in Blast Scenarios

ABSTRACTUse of silicone adhesives for structural bonding of glass panels to metallic frame is a well‐established technology in façade applications. Selection of silicone technology is mainly driven by the unique UV resistance and thermal stability offered. However, are these the only factors that can drive technology selection in facade applications? Comprehensive experience gained by Sika over the last 50 years for applications in the Transportation Industry proves that polyurethane (PU) technology can offer valuable opportunities also for structural glazing applications in façades, although PU are usually more sensitive to UV radiations. Provided that existing protective measures are implemented to control UV exposure of bond lines, potential of PU technology in facades can be significant. In this paper, mechanical and application properties of Sikaflex®‐268 PU adhesive are presented and compared to Sikasil® SG‐500, a typical silicone used for structural glazing applications in facades. Comparison of mechanical behavior is based on tests performed at different temperatures, after curing as well as after accelerated aging. Results prove outstanding mechanical performance of Sikaflex®‐268 versus Sikasil® SG‐500, making the PU adhesive especially suitable for those systems where needs for transferring high loads exist. In blast scenarios, Sikaflex®‐268 high‐strength performance under highspeed deformations can introduce significant opportunities for joint reduction or for extending design feasibility in critical systems. Benefits offered by Sikaflex®‐268 are not only limited to its mechanical performance but also to the available application solutions. Boostered version of the product exist for both pump equipment and gun dispenser, with two major advantages in façade applications: a) fast curing during production as well as site applications or reglazing b) no limitations in joint dimensions, which confirms the adhesive potential for design in blast scenarios

Perspective semiconductor materials for the using in the power electronics

The world market of discrete power devices in 2024 will be ~ $ 23 billion, the share of devices based on silicon will be ~ 87%, due to the price availability and the mastery of silicon technologies. The inflow of investments, the success in mastering SiC, GaN, diamond, heterostructure technologies, and the pressing need for the manufacture of new high-temperature, radiation-resistant power semiconductor devices (PSs) with better performance and frequency characteristics, in comparison with silicon devices, contribute to the growing popularity of these materials from manufacturers of devices. The pressure of legislative and commercial requirements related to energy efficiency and cost reduction contributes to the successful development of a new element base using these materials for the fifth generation (5G) communication networks, broadband Internet access systems, satellite systems, microwave transmitters, civil and military radar stations, for energy and transport. However, the possibilities of silicon in terms of increasing thermostability, radiation resistance, reliability of PSs and industrial development are far from exhaustion. Methods for the special alloying of CZ-Si single crystals and for processing, improving the mechanical properties of single crystals, as well as evidence of an increase in the radiation and thermal stability of silicon-based PSs are proposed.

Insect-inspired neuromorphic computing.

The steady improvement in the performance of computing systems seen for many decades is levelling off as the miniaturization of semiconducting technology approaches the atomic limit, facing severe physical and technological issues. Neuromorphic computing is an emerging solution which makes use of silicon technology in a different way, inline with the computational principles observed in animal nervous systems. In this article, we argue that the nervous systems of insects in particular offer themselves as an ideal starting point for incorporation into realistic neuromorphic systems and review research in developing insect-inspired neuromorphic systems. We conclude with an exciting yet tangible vision of a full neuromorphic sensory-motor system where a liquid state machine modelling the function of the insect mushroom body links input to output and allows for amalgamation of the work discussed in a hierarchical framework of a full system inspired by the concept of how information flows through insects.

Comparison of techniques for detecting metal contamination in silicon wafers

In this work we present the results of experiments aimed at comparing the performances of various techniques for the detection of metal contamination in the silicon technology. Techniques for the measurement of surface contamination such as Total Reflection X-Ray Fluorescence (TXRF) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) are compared with techniques for the measurement of contamination in the silicon volume, specifically the Deep Level Transient Spectroscopy and techniques for the measurement of carrier lifetime. Carrier lifetime measurements were obtained by photocurrent measurements and by Surface Photovoltage measurements.In a first experiment, Synchrotron-Radiation TXRF (SR-TXRF) was used as the reference technique to assess the sensitivity of a commercial TXRF instrument and of carrier lifetime measurements to detect iron contamination in wafers cleaned by ordinary cleaning processes.Samples intentionally contaminated by spinning with various elements were used for another experiment comparing TXRF and ToF-SIMS measurements of surface contamination.Then, a few case studies are discussed, specifically tungsten contamination by sputtering in ion-implanted samples and palladium contamination due to contact with a contaminated chuck.In all these experiments, advantages and disadvantages of the different techniques are discussed. The results of this study clearly show that it is not possible to define a unique recipe that can be applied in all cases. The maximum tolerated contaminant concentration per unit area depends on the contaminant diffusivity, and is much lower for slow diffusers. The contaminant diffusivity and solid solubility in silicon determine the in-depth distribution of the contaminant, and hence the most effective approach.

Band structure and absorption properties of (Ga, In)/(P, As, N) symmetric and asymmetric quantum wells and super-lattice structures: Towards lattice-matched III-V/Si tandem

Quaternary dilute nitride compound semiconductors like GaAsyP1−x−yNx and Ga1−zInzP1−xNx are lattice matched with silicon when y = 4.7 * x − 0.1 and z = 2.2 * x − 0.044 and also have direct bandgaps (with N &amp;gt; 0.6%), thus allowing for monolithic integration of III-V optoelectronics with silicon technology as well as III-V/Si tandem junction solar cells. By applying an eight-band k.p strained (tensile or compressive) Hamiltonian and a Band Anti-crossing model (to account for small amounts of nitrogen impurities) to the conduction band, the electronic band structure and the dispersion relation of these alloys can be determined near the center of Brillouin Zone. In this work, by minimizing the total mechanical energy of the stack of alternating layers of GaP1−xNx and GaAs1−xNx, we have evaluated the ratio of thickness of the respective layers for a strain-balanced superlattice GaAs1−xNx/GaP1−xNx structure on silicon. We calculated the confinement energies and the corresponding states of the respective carriers inside a quantum well (with and without resonantly coupled) or in the miniband of a superlattice structure as a function of the nitrogen composition using a transfer matrix approach under the envelope function approximation. Incorporating only a small amount of nitrogen (&amp;lt;5%), the bandgap of these lattice matched structures fulfils the optimum bandgap requirement of (1.65–1.8) eV for III-V/Si tandem solar cells and optoelectronic devices. The optical-absorption coefficient, in both symmetric and asymmetric quantum wells, is then evaluated with respect to nitrogen composition and temperature by using the Fermi-golden rule for both TE and TM polarization of incident light, including the effect of excitons and thermal broadening.

Pathways for mitigating thermal losses in solar photovoltaics

To improve the performance of solar photovoltaic devices one should mitigate three types of losses: optical, electrical and thermal. However, further reducing the optical and electrical losses in modern photovoltaic devices is becoming increasingly costly. Therefore, there is a rising interest in minimizing the thermal losses. These correspond to the reduction in electrical power output resultant of working at temperatures above 25 °C and the associated accelerated aging. Here, we quantify the impact of all possible strategies to mitigate thermal losses in the case of the mainstream crystalline silicon technology. Results indicate that ensuring a minimum level of conductive/convective cooling capabilities is essential. We show that sub-bandgap reflection and radiative cooling are strategies worth pursuing and recommend further field testing in real-time operating conditions. The general method we propose is suitable for every photovoltaic technology to guide the research focused on reducing thermal losses.

Comparison of 5-GHz Quadrature Couplers Using GaAs and Silicon-Based IPD Technologies

The 5-GHz quadrature couplers implemented in GaAs and silicon-based integrated passive device (IPD) technologies are presented. Although GaAs technology is superior to silicon-based technology in terms of substrate resistivity and back-side vias, the quadrature coupler using a silicon IPD process achieved better insertion loss due to thick metal traces and comparable substrate resistivity. While the coupler using the GaAs process employed 4- $\mu \text{m}$ -thick metal traces, the coupler using silicon IPD technology employed 10.8- $\mu \text{m}$ -thick traces realized with via connections between a top metal of 5.3- $\mu \text{m}$ thickness and a bottom metal of 5.5- $\mu \text{m}$ thickness. The couplers using the silicon and GaAs IPD process technologies showed 0.15 and 0.27 dB of insertion loss, respectively. Also, the silicon IPD design uses a slightly different topology which splits a coupled inductor into two coupled inductors with shunt capacitors to achieve a broader distributed bandwidth.

Artificial intelligence technique for estimating PV modules performance ratio under outdoor operating conditions

In this paper, artificial neural networks (ANNs) have been used for the performance ratio modelling of four photovoltaic (PV) modules. The PV modules are selected from three different silicon technologies including one monocrystalline, two polycrystalline, and one micromorph (a-Si/μc-Si) modules. The adopted ANN architecture is a multilayer perceptron (MLP). The inputs of the ANN models are the solar irradiance on the PV module plane and air ambient temperature, while the output is the PV module performance ratio. It is shown that ANN models with three layers and five hidden neurons accurately model the performance ratio regardless of PV module technology. The results obtained from the ANN model are compared with those obtained from the five parameter model (L5P). The model comparison is done through two widely used forecasting errors: the root mean square error (RMSE) and the mean absolute percentage of error (MAPE). The values of both RMSE and MAPE are less than 0.02 for MLP based models and are about three to nine times lower than those obtained from the electrical model. It is also shown that the poor fit of the L5P model is due to the bad estimation of series and shunt resistances.

Design, fabrication and characterization of laser patterned LTCC micro hotplate with stable interconnects for gas sensor platform

The present paper presents design, fabrication and characterization of low temperature co-fired ceramics (LTCC)-based micro hotplates. Laser irradiation is used to pattern fired conductive paste over LTCC substrate to generate fine meander shaped heater patterns. These micro hotplates consumes low power (~ 500 mW for 300 °C) compared to standard alumina technology due to low thermal conductivity (3–4 W/(m-K) of LTCC substrate. This technology is inexpensive for small series compared production as compared to the silicon technology. The structuring ability of LTCC green tapes is utilized to provide dedicated through via-holes in micro hotplate design which lowers the thermal mass and helps in providing special fused electrical interconnects. These connections are found thermally stable and results are very promising. Thermal properties such as temperature distribution and power consumption have been investigated using FEM (Finite Element Method) simulations on COMSOL software.