191 results about "Critical thickness" patented technology

In all representative embodiments presented, the Ge concentration in the source and drain 10 and the SiGe epitaxial channel layer 20 is in the 15% to 50% range, preferably between about 20% to 40%. The SiGe thicknesses in the source / drain 10 are staying below the critical thickness for the given Ge concentration. The critical thickness is defined such that above it the SiGe will relax and defects and dislocations will form. The thickness of the SiGe epitaxial layer 20 typically is between about 5nm and 15nm. The thickness of the epitaxial Si layer 30 is typically between about 5nm and 15nm. FIG. 1A shows an embodiment where the body is bulk Si. These type of devices are the most common devices in present day microelectronics. FIGS. 1B and 1C show representative embodiment of the heterojunction source / drain FET device when the Si body 40 is disposed on top of an insulating material 55. This type of technology is commonly referred to as silicon on insulator (SOI) technology. The insulator material 55 usually, and preferably, is SiO2. FIG. 1B shows an SOI embodiment where the body 40 has enough volume to contain mobile charges. Such SOI devices are called partially depleted devices. FIG. 1C shows an SOI embodiment where the volume of the body 40 is insufficient to contain mobile charges. Such SOI devices are called fully depleted devices. For devices shown in FIG. 1B and 1C there is, at least a thin, layer of body underneath the source and drain 10. This body material serves as the seed material onto which the epitaxial SiGe source and drain 10 are grown. In an alternate embodiment, shown in FIG. 1D. for extremely thin fully depleted SOI devices, one could grow the source and drain 10 laterally, from a lateral seeding, in which case the source and drain 10 would penetrate all the way down to the insulating layer 55.

A semiconductor device includes a single crystal substrate and a dielectric layer overlying the substrate. The dielectric layer includes at least one opening having a first portion and an overlying second portion. The first portion has a depth and width, such that an aspect ratio of the depth to width is greater than one. The semiconductor device further includes a first material having a first portion and a second portion, the first portion of the first material filling the first portion of the at least one opening. Defects for relaxing strain at an interface between the first material and the substrate material exist only within the first portion of the first material due to the aspect ratio being greater than one. The second portion of the first material is substantially defect free. Furthermore, the second portion of the first material and an overlying second material different than the first material fill the overlying second portion of the at least one opening. The second material has a thickness which is less than a critical thickness to maintain the second material in a strained state. The strained second material functions as a channel for charge carriers.

Composite optical waveguide structures or mode transformers and their methods of fabrication and integration are disclosed, wherein the structures or mode transformers are capable of bi-directional light beam transformation between a small mode size waveguide and a large mode size waveguide. One aspect of the present invention is directed to an optical mode transformer comprising a waveguide core having a high refractive index contrast between the waveguide core and the cladding, the optical mode transformer being configured such that the waveguide core has a taper wherein a thickness of the waveguide core tapers down to a critical thickness value, the critical thickness value being defined as a thickness value below which a significant portion of the energy of a light beam penetrates into the cladding layers surrounding the taper structure thereby enlarging the small mode size. This primary tapered core structure may be present in either a vertical or horizontal direction and may be combined with further up taper or down taper structures in the directions transverse to the primary taper direction. Another aspect of the present invention is directed to a non-cylindrical graduated refractive index (GRID) lens structure. The non-cylindrical GRIN structure has a graded refractive index having a maximum value at its core and a minimum value at its outer edges. The grading of the refractive index is provided in a either the vertical or horizontal directions and may have either a fixed refractive index or a graded refractive index in the transverse directions. Yet another aspect of the present invention is directed to composite optical mode transformers that are combinations of the taper waveguide structures and the non-cylindrical graduated refractive index structures. Yet another aspect of the present invention is the further integration of the mode transformers with V-grooves for multiple input / output fibers and alignment platform for multiple input / output photonic chips or devices.

A photovoltaic cell to convert low energy photons is described, consisting of a p-i-n diode with a strain-balanced multi-quantum-well system incorporated in the intrinsic region. The bandgap of the quantum wells is lower than that of the lattice-matched material, while the barriers have a much higher bandgap. Hence the absorption can be extended to longer wavelengths, while maintaining a low dark current as a result of the higher barriers. This leads to greatly improved conversion efficiencies, particularly for low energy photons from low temperature sources. This can be achieved by strain-balancing the quantum wells and barriers, where each individual layer is below the critical thickness and the strain is compensated by quantum wells and barriers being strained in opposite directions minimizing the stress. The absorption can be further extended to longer wavelengths by introducing a strain-relaxed layer (virtual substrate) between the substrate and the active cell.

A semiconductor structure includes an n-type region, a p-type region, and a III-nitride light emitting layer disposed between the n-type region and the p-type region. The III-nitride light emitting layer has a lattice constant greater than 3.19 Å. Such a semiconductor structure may be grown on a substrate including a host and a seed layer bonded to the host. In some embodiments, a bonding layer bonds the host to the seed layer. The seed layer may be thinner than a critical thickness for relaxation of strain in the semiconductor structure, such that strain in the semiconductor structure is relieved by dislocations formed in the seed layer, or by gliding between the seed layer and the bonding layer an interface between the two layers. In some embodiments, the host may be separated from the semiconductor structure and seed layer by etching away the bonding layer.

In a field effect transistor, an Si layer, an SiC (Si1-yCy) channel layer, a CN gate insulating film made of a carbon nitride layer (CN) and a gate electrode are deposited in this order on an Si substrate. The thickness of the SiC channel layer is set to a value that is less than or equal to the critical thickness so that a dislocation due to a strain does not occur according to the carbon content. A source region and a drain region are formed on opposite sides of the SiC channel layer, and a source electrode and a drain electrode are provided on the source region and the drain region, respectively.

A light-emitting semiconductor device comprises a III-Nitride active region and a III-Nitride layer formed proximate to the active region and having a thickness that exceeds a critical thickness for relaxation of strain in the III-Nitride layer. The III-Nitride layer may be a carrier confinement layer, for example. In another aspect of the invention, a light-emitting semiconductor device comprises a III-Nitride light emitting layer, an InxAlyGa1-x-yN (0≦x≦1, 0≦y≦1, x+y≦1), and a spacer layer interposing the light emitting layer and the InxAlyGa1-x-yN layer. The spacer layer may advantageously space the InxAlyGa1-x-yN layer and any contaminants therein apart from the light emitting layer. The composition of the III-Nitride layer may be advantageously selected to determine a strength of an electric field in the III-Nitride layer and thereby increase the efficiency with which the device emits light.

A solar cell with a superlattice structure and a fabricating method thereof are provided, which includes fabricating a superlattice structure of GaAsN / GaInAs, GaAsN / GaSbAs, or GaAsN / GaInSbAs between a base and an emitter of a middle cell of a triple junction solar cell by a strain-compensation technology. The provided solar cell not only decreases crystalline defects and increases the critical thickness of the crystal, but also makes the energy bandgap of GaAsN and GaInAs reach around the energy of 1.0 eV (electron volt). Hence, the absorption region can be raised to around the energy of 1.0 eV to enhance the efficiency of the solar cell.

The present invention describes a method including: providing a substrate; forming an underlying layer over the substrate; heating the substrate; forming a ferroelectric layer over the underlying layer, the ferroelectric layer having a thickness below a critical thickness, the underlying layer having a smaller lattice constant than the ferroelectric layer; cooling the substrate to room temperature; and inducing a compressive strain in the ferroelectric layer.

A thin blanket epitaxial layer of SiGe is grown on a silicon substrate to have a biaxial compressive stress in the growth plane. A thin epitaxial layer of silicon is deposited on the SiGe layer, with the SiGe layer having a thickness less than its critical thicknesses. Shallow trenches are subsequently fabricated through the epitaxial layers, so that the strain energy is redistributed such that the compressive strain in the SiGe layer is partially relaxed elastically and a degree of tensile strain is induced to the neighboring layers of silicon. Because this process for inducing tensile strain in a silicon over-layer is elastic in nature, the desired strain may be achieved without formation of misfit dislocations.

What is described here is a method of manufacturing spectacles comprising individual progressive ophthalmic lenses, including the following steps:selection of a spectacle frame,detection of the shape of the lens rings with a precision better than ±0.5 mm in the x- and y-directions (data set 1),detecting the intersection points of the lines of sight through the plane of the lens rings for at least two design distances of the progressive ophthalmic lenses with a precision better than ±1 mm (data set 2)selection and positioning relative to the lens rings of a spherical or non-spherical surface in view of the prescription data, using the data sets 1 and 2 (data set 3),computing and positioning the progressive surface relative to the selected surface, with minimization of the critical thickness of the ophthalmic lens, using the data sets 1 to 3 (data set 4),manufacturing the progressive surfaces as well as edges of the ophthalmic lenses from a non-edged semi-finished product finished on one side, using the data sets 1 to 4.

A semiconductor light emitting device is disclosed, including a semiconductor substrate, an active region comprising a strained quantum well layer, and a cladding layer for confining carriers and light emissions, wherein the amount of lattice strains in the quantum well layer is in excess of 2% against either the semiconductor substrate or cladding layer and, alternately, the thickness of the quantum well layer is in excess of the critical thickness calculated after Matthews and Blakeslee.

A semiconductor light emitting device is disclosed, including a semiconductor substrate, an active region comprising a strained quantum well layer, and a cladding layer for confining carriers and light emissions, wherein the amount of lattice strains in the quantum well layer is in excess of 2% against either the semiconductor substrate or cladding layer and, alternately, the thickness of the quantum well layer is in excess of the critical thickness calculated after Matthews and Blakeslee.

The invention discloses special structural explosive for explosive cladding, an explosive cladding method and an explosive cladding device. The structural explosive comprises a filling plate, a plurality of cavities filled with the explosive are formed in the filling plate and distributed in a matrix. The special structural explosive for explosive cladding is formed by filling or injecting the explosive in the cavities of the filling plate. A layer of composite plate is mounted on each of two sides of the structural explosive, and the two composite plates are driven to move reversely after explosion to composite with two base plates in reserve directions. By the aid of an explosive filling method, explosive filling quality is guaranteed, critical thickness of stable explosive detonation is reduced, and energy utilization rate of explosive explosion is improved. The special structural explosive is convenient to use, and mechanized batch production can be realized. By the aid of the explosive cladding device, usage amount of the explosive is lowered, production cost is reduced, shock wave and noise pollution are reduced, and working environment of workers is improved.

Method to produce a structure consisting of depositing a material by columnar epitaxy on a crystalline face of a substrate (2), of continuing so that the columns (4) give a continuous layer (5). The surface is provided with a period array of bumps (3) on a nanometric scale, each bump (3) having a support zone (35) and being obtained from an array of crystalline defects and / or strain fields created within a crystalline region (16) located in the vicinity of a bonding interface (15) between two crystalline elements (11, 12) whose crystalline lattices have a twist and / or tilt angle and / or have interfacial lattice mismatch, able to condition the period (38) of the array of bumps (3). The period (38) of the array, the height (36) of the bumps and the size of their support zone (35) being adjusted so that the continuous layer (40) has a critical thickness that is greater than that obtained using epitaxy without the bumps.