Evolution of interfacial defects by H/He co-implantation in 300 mm SOI layer transfer process

A novel fabrication process of ferroelectric-semiconductor heterostructures based on direct wafer bonding (DWB) and layer transfer is proposed. Metal-ferroelectric-silicon (MFS) structures were fabricated by both layer transfer process and direct deposition of ferroelectric films onto Si. Detailed transmission electron microscope (TEM) investigations revealed that a direct wafer bonding and layer transfer process yields good quality ferroelectric/Si interfaces. Interface trap measurements show a large difference for MFS structures fabricated by bonding or by direct deposition, respectively. The trap density values were ranging from 2×1012 cm−2eV−1 for SBT/Si directly deposited to 4×1011 cm−2eV−1 for SBT/Si bonded interfaces.

The structural and morphological modifications induced by the carbonization stage upon 3C-SiC heteroepitaxial films grown on (111) and (100) oriented silicon substrates have been investigated. The crystalline quality of the films is strongly dependent on the carbonization parameters (propane flow rate and duration of carbonization). The (111) heteroepitaxial films coalesce more rapidly and present a lower dependence on the carbonization conditions than (100) films. By comparing the evolution of the interfacial defects (voids) density with existing models, we show that this is related to the initial mechanisms occurring during the carbonization stage. The twin defects densities on (111), (100) and (211) films are also investigated and the role of the only carbonization stage on their formation is studied.

We investigate the origin of transverse cracks often observed in thin films obtained by the layer transfer technique. During this process, two crystals bonded to each other containing a weak plane produced by ion implantation are heated to let a thin layer of one of the material on the other. The level of stress imposed on the film during the heating phase due to the mismatch of thermal expansion coefficients of the substrate and the film is shown to be the dominent factor in determining the quality of the transferred layer. In particular, it is shown that if the film is submitted to a tensile stress, the microcracks produced by ion implantation are not stable and deviate from the plane of implantation making the layer transfer process impossible. However, if the compressive stress exceeds a threshold value, after layer transfer, the film can buckle and delaminate, leading to transverse cracks induced by bending. As a result, we show that the imposed stress σm—or equivalently the heating temperature—must be within the range −σc<σm<0 to produce an intact thin film where σc depends on the interfacial fracture energy and the size of defects at the interface between film and substrate.

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High-performance GaInP/AlGaInP multi-quantum well light-emitting diodes (LEDs) grown on a low threading dislocation density (TDD) germanium-on-insulator (GOI) substrate have been demonstrated. The low TDD of the GOI substrate is realized through Ge epitaxial growth, wafer bonding, and layer transfer processes on 200 mm wafers. With O2 annealing, the TDD of the GOI substrate can be reduced to ∼1.2×106 cm−2. LEDs fabricated on this GOI substrate exhibit record-high optical output power of 1.3 mW at a 670 nm peak wavelength under 280 mA current injection. This output power level is at least 2 times higher compared to other reports of similar devices on a silicon (Si) substrate without degrading the electrical performance. These results demonstrate great promise for the monolithic integration of visible-band optical sources with Si-based electronic circuitry and realization of high-density RGB (red, green, and blue) micro-LED arrays with control circuitry.

We demonstrate for the first time the successful layer transfer of an epitaxially grown monocrystalline Si film from a purely chemically etched porous Si substrate of 150 mm diameter to a glass carrier. The surface conditioning for all Si layer transfer processes based on porous Si has been, up to now without exception, carried out by electrochemical etching. In contrast, our chemical stain etching process uses an aqueous HF-rich HF/HNO3 solution. The porosity increases with increasing doping concentration of the Si substrate wafer and with increasing porous layer thickness. In contrast to the electrochemically etched double layers, the porosity profile of the stain etched substrates is highest at the original wafer surface and lowest at the interface between the porous layer and the Si bulk. The epitaxy process is adapted to the high porosity at the surface with regard to the reorganization of the porous layer.

A germanium-based platform with a large core-clad index contrast, germanium-on-silicon nitride waveguide, is demonstrated at mid-infrared wavelength. Simulations are performed to verify the feasibility of this structure. This structure is realized by first bonding a silicon-nitride-deposited germanium-on-silicon donor wafer onto a silicon substrate wafer, followed by the layer transfer approach to obtain germanium-on-silicon nitride structure, which is scalable to all wafer sizes. The misfit dislocations which initially form along the interface between germanium/silicon can be removed by chemical mechanical polishing after layer transfer process resulting in a high-quality germanium layer. At the mid-infrared wavelength of 3.8 μm, the germanium-on-silicon nitride waveguide has a propagation loss of 3.35 ± 0.5 dB/cm and a bend loss of 0.14 ± 0.01 dB/bend for a radius of 5 μm for the transverse-electric mode.

The influence of the method used for preparing As2Se3 amorphous layers on the processes of charge transfer and charge accumulation in these structures is studied. Different physical parameters, such as the contact capacitance, the width of the charge accumulation region, and the time of transit of charge carriers through the samples, which characterize the occurring electronic processes, are determined for the layers under investigation.

Enhanced photocatalytic hydrogen production activity of Janus Cu1.94S-ZnS spherical nanoheterostructures

Thermally driven redistribution of phases and components in Cu/Sn thin films

The article is part of 4th cycle of articles under the general title “Heat transfer in the enclosing structures of a blast furnace”. In Part 1, with the subheading “Statement of the problem and the prerequisites for calculation”, typical multiwalled enveloping structures of a blast furnace are considered. The description of the layers in these structures is given. The main attention is paid to the lining layer. Briefly described the process of smelting cast iron and temperature conditions in the characteristic layers of the internal environment of the furnace. Based on the theory of A.V. Lykov, the initial equations describing the interconnected transfer of heat and mass in a solid are analyzed in relation to the problem posed (a proper description of the processes for the purpose of further rational design of the multilayered enclosing structure of the blast furnace). A priori enclosure from the mathematical point of view is considered as an unlimited plate. In Part 2 with the subtitle “Solving the boundary-value problems of heat transfer,” the boundary-value problems of heat transfer in separate layers of the design with various boundary conditions are considered, and their solutions are given that are basic in the development of the mathematical model of the nonstationary heat transfer process in a multilayered enclosing structure. Part 3 presents a mathematical model of the process of heat transfer in the enclosure and an algorithm for its implementation. The proposed mathematical model allows to solve the following problems: - assess the thermophysical state of the designed structures under different operating conditions and, as a consequence, rationally design them for a particular mode or range of modes; - to calculate the temperature field in complex multi-layer constructions, for example, when the arrangement of the layers is discrete; - when temperature is measured at characteristic points (at the joints of layers and structural surfaces), it is possible to determine the thermophysical characteristics of the materials constituting the surveyed structure; - in laboratory tests it is possible to significantly shorten the test time, the researchers have the opportunity not to wait for the establishment of a regular regime; - it becomes possible to abandon the climate chamber and expensive instrumentation for experiments and research; - when solving the inverse problem, directly determine the resistance to heat transfer of the entire layered structure and its individual layers from the unsteady temperature field. Part 4 gives a number of examples of calculation of the heat transfer process in a multiwalled fencing of a blast furnace, which show the effectiveness of the proposed calculation procedure.

Potassium magnesium phosphate cement (MKPC) has important application value in rapid structural repair engineering due to its fast hardening and high strength. To further explore the bonding mechanism of the Mortar‐MKPC interface, the three‐point bending (TPB) test combined with digital image correlation (DIC) technology was used to systematically study the influence mechanism of the defect scale effect and MKPC hydration process on interface bonding performance. By quantitatively analyzing the strain field evolution and crack initiation characteristics of composite materials under different curing cycles (3d, 7d, and 28d) and defect parameters (a0 is 0.1, 0.2, and 0.3, respectively), we found that the interfacial bond strength increases significantly with the curing age. Based on the finite element method, the complex stress intensity factor of the interface crack tip of the bi‐material was calculated. The results showed that the parameters of the interface crack of the specimen are mainly dominated by the normal stress (K1), and the shear stress (K2) had little effect. The microstructure of the interface was characterized by SEM‐EDS, and the densification and gel phase of hydration products increased with the increase of age. The interfacial bonding strength and elastic modulus of B28‐4 are 2.3 and 1.2 times that of B3‐4, respectively. Mortar‐MKPC composites showed higher crack propagation resistance (Wpre) in the middle stage (7d), and its value was 45.7% higher than that of MKPC samples when a0 was 0.1. By analyzing the coupling mechanism of hydration development and defect evolution of materials in interface failure, it is helpful to provide a theoretical basis for the rapid repair of civil infrastructure and sustainable applications.

Epitaxial layer transfer was used to fabricate In/sub 0.53/Ga/sub 0.47/As-InP avalanche photodiodes on GaAs substrates. The photodiodes displayed a gain-bandwidth product of 80 GHz, dark current of 10.20 nA at 90% of the breakdown voltage, and responsivity of 5.9 A/W at 2 V below breakdown. Performance is comparable to standard devices fabricated on InP substrates, suggesting the transfer process does not degrade material quality.

Converting CO2 to multi-carbon products at >1 A/cm2 using gas diffusion electrode based on commercial materials via transfer process engineering

Optical interconnects, enabled by electronic-photonic integrated circuits (EPICs), has been proposed as a potential solution to the latency, bandwidth and power density bottlenecks of the conventional metal interconnects in complementary metal-oxide-semiconductor (CMOS) integrated circuits. Optoelectronic components such as photodetector is one of the key building blocks, converting optical signals into electrical ones, to realize such a platform. Germanium (Ge), thanks to its CMOS-compatibility and considerable optical absorption at tele-communication wavelengths, has been widely studied for integrated photodetectors on silicon (Si). In recent years, germanium-on-insulator (GOI) has attracted significant attention. The intermediate insulator layer can play several vital roles: 1) preventing carrier cross-talk and material inter-diffusion between Ge and the underlying Si; 2) enabling a stronger optical confinement in the top Ge for sensing and communication at mid-infrared wavelengths (3 to 14 µm); 3) enhancing electrostatic control for Ge CMOS; 4) facilitating a dense three-dimensional back-end-of-line (BEOL) electronic-photonic integration. The quality of Ge can also be generally improved compared to that from direct epitaxy, which could help reduce the dark current noise from the photodetectors. However, state-of-the-art photodetectors on GOI are reported with limited quantum efficiency (QE). This is due to their planar deployment of the contacts at the Ge surface that is inefficient in collecting the deep photon-generated carriers. In this thesis, a method to realize a vertical p-i-n structure in GOI, using silicon dioxide (SiO2) as the insulator layer, was developed by ion-implanting boron at one side of an epitaxial-grown Ge layer, followed by arsenic at the other side, along with a bonding and layer transfer process for the GOI fabrication. The vertical p-i-n structure builds a vertical electric field across the Ge layer for an efficient carrier collection. Abrupt doping profiles were verified in the transferred high-quality Ge layer. The photodetectors exhibit a dark current density of∼47 mA/cm2 at −1V and an optical responsivity of 0.39 A/W at 1550 nm, which are prominently improved compared to state-of-the-art GOI photodetectors. An internal quantum efficiency (IQE) of ∼97% indicates an excellent carrier collection efficiency. The experimental 3-dB bandwidth of ∼1 GHz agrees well with the theoretical calculation including series resistance and parasitic capacitance of the device. The bandwidth is expected to reach ∼32 GHz with an optimized contact resistance as well as mesa diameter. In addition, an improved QE was also demonstrated in uniformly tensile-strained GOI photodetectors. The tensile strain reduces the Ge bandgap and increases its band-to-band absorption coefficient, enabling an enhanced QE particularly at the tele-communication L-band (1,565 to 1,625 nm) and beyond. The uniform tensile strain is achieved by a patented recessed approach in placing silicon nitride (SiNx) sidewall stressor. A self-aligned dry etching (SADE) method was introduced to remove the insulator (SiO2) layer during the Ge waveguide-on-insulator (WGOI) patterning, followed by placing the tensile-stressed SiNx stressor at the waveguide sidewalls. A tensile strain of ~0.7% with an enhanced uniformity was observed from the Ge WGOI with a 580 MPa-tensile SiNx stressor, using micro-Raman measurements, along the transverse direction of the waveguide. The corresponding metal-semiconductor-metal (MSM) photodetectors exhibit a ~70nm extension of the absorption coverage towards longer wavelengths and a ~2× enhancement on the QE (as well as the absorption coefficient) at 1,620 nm. An additional ~37% QE improvement was also established, compared to the detectors without employing SADE. Theoretical calculation tells that a 1.5 GPa-tensile stressor could extend the Г-valley-heavy-hole and -light-hole bandgap edges towards ~1,665 and ~1,710 nm, respectively, covering the entire tele-communication bands. The results potentially facilitate a high-bandwidth and high-efficiency GOI photodetector at BEOL for integrated photonics. Suggestions have also been given to further improve the device performance. Furthermore, the concept of uniformly-straining Ge can be extended for the bandgap engineering of other semiconductor materials such as III-V and GeSn for a wide range of optoelectronic applications including light sources, electro-absorption modulators and photodetectors.