1233 results about "Lattice mismatch" patented technology

A monolithic, multi-bandgap, tandem solar photovoltaic converter has at least one, and preferably at least two, subcells grown lattice-matched on a substrate with a bandgap in medium to high energy portions of the solar spectrum and at least one subcell grown lattice-mismatched to the substrate with a bandgap in the low energy portion of the solar spectrum, for example, about 1 eV.

In one embodiment, a method of forming a multijunction solar cell having lattice mismatched layers and lattice-matched layers comprises growing a top subcell having a first band gap over a growth semiconductor substrate. A middle subcell having a second band gap is grown over the top subcell, and a lower subcell having a third band gap is grown over the middle subcell. The lower subcell is substantially lattice-mismatched with respect to the growth semiconductor substrate. The first band gap of the top subcell is larger than the second band gap of the middle subcell. The second band gap of the middle subcell is larger than the third band gap of the lower subcell. A support substrate is formed over the lower subcell, and the growth semiconductor substrate is removed. In various embodiments, the multijunction solar cell may further comprise additional lower subcells. A parting layer may also be provided between the growth substrate and the top subcell in certain embodiments. Embodiments of this reverse process permit the top and middle subcells to have high performance by having atomic lattice spacing closely matched to that of the growth substrate. Lower subcells can be included with appropriate band gap, but with lattice spacing mismatched to the other subcells. The reduced performance caused by strain resulting from mismatch can be mitigated without reducing the performance of the upper subcells.

Low-bandgap, monolithic, multi-bandgap, optoelectronic devices (10), including PV converters, photodetectors, and LED's, have lattice-matched (LM), double-heterostructure (DH), low-bandgap GaInAs(P) subcells (22, 24) including those that are lattice-mismatched (LMM) to InP, grown on an InP substrate (26) by use of at least one graded lattice constant transition layer (20) of InAsP positioned somewhere between the InP substrate (26) and the LMM subcell(s) (22, 24). These devices are monofacial (10) or bifacial (80) and include monolithic, integrated, modules (MIMs) (190) with a plurality of voltage-matched subcell circuits (262, 264, 266, 270, 272) as well as other variations and embodiments.

A strained-channel transistor structure with lattice-mismatched zone and fabrication method thereof. The transistor structure includes a substrate having a strained channel region, comprising a first semiconductor material with a first natural lattice constant, in a surface, a gate dielectric layer overlying the strained channel region, a gate electrode overlying the gate dielectric layer, and a source region and drain region oppositely adjacent to the strained channel region, with one or both of the source region and drain region comprising a lattice-mismatched zone comprising a second semiconductor material with a second natural lattice constant different from the first natural lattice constant.

Structures and methods for their formation include a substrate comprising a first semiconductor material, with a second semiconductor material disposed thereover, the first semiconductor material being lattice mismatched to the second semiconductor material. Defects are reduced by using an aspect ratio trapping approach.

A method of forming a multijunction solar cell comprising an upper subcell, a middle subcell, and a lower subcell comprising providing first substrate for the epitaxial growth of semiconductor material; forming a first solar subcell on said substrate having a first band gap; forming a second solar subcell over said first subcell having a second band gap smaller than said first band gap; and forming a grading interlayer over said second subcell having a third band gap larger than said second band gap forming a third solar subcell having a fourth band gap smaller than said second band gap such that said third subcell is lattice mismatched with respect to said second subcell.

A p-type field effect transistor (PFET) and an n-type field effect transistor (NFET) of an integrated circuit are provided. A first strain is applied to the channel region of the PFET but not the NFET via a lattice-mismatched semiconductor layer such as silicon germanium disposed in source and drain regions of only the PFET and not of the NFET. A process of making the PFET and NFET is provided. Trenches are etched in the areas to become the source and drain regions of the PFET and a lattice-mismatched silicon germanium layer is grown epitaxially therein to apply a strain to the channel region of the PFET adjacent thereto. A layer of silicon can be grown over the silicon germanium layer and a salicide formed from the layer of silicon to provide low-resistance source and drain regions.

A semiconductor structure comprises a substrate comprising a first crystalline semiconductor material, a dielectric layer, above the substrate, defining an opening, a second crystalline semiconductor material at least partially filling the opening, and a crystalline interlayer between the substrate and the second crystalline semiconductor material. The first crystalline semiconductor material and the second crystalline semiconductor material are lattice mismatched, and the crystalline interlayer comprises an oxygen compound. A method for fabricating semiconductor structure comprises the steps of providing a substrate including a first crystalline semiconductor material, patterning an opening in a dielectric layer above the substrate, the opening having a bottom, forming a crystalline interlayer on the substrate at least partially covering the bottom, and growing a second crystalline semiconductor material on the crystalline interlayer thereby at least partially filling the opening. The crystalline semiconductor materials are lattice mismatched, and the crystalline interlayer comprises an oxygen compound.

Growth of multilayer films is carried out in a manner which allows close control of the strain in the grown layers and complete release of the grown films to allow mounting of the released multilayer structures on selected substrates. A layer of material, such as silicon-germanium, is grown onto a template layer, such as silicon, of a substrate having a sacrificial layer on which the template layer is formed. The grown layer has a lattice mismatch with the template layer so that it is strained as deposited. A top layer of crystalline material, such as silicon, is grown on the alloy layer to form a multilayer structure with the grown layer and the template layer. The sacrificial layer is preferentially etched away to release the multilayer structure from the sacrificial layer, relaxing the grown layer and straining the crystalline layers interfaced with it.

Monolithic lattice-mismatched semiconductor heterostructures are fabricated by bonding patterned substrates with alternative active-area materials formed thereon to a rigid dielectric platform and then removing the highly-defective interface areas along with the underlying substrates to produce alternative active-area regions disposed over the insulator and substantially exhausted of misfit and threading dislocations.

A method of forming a multijunction solar cell including an upper subcell, a middle subcell, and a lower subcell, the method including: providing first substrate for the epitaxial growth of semiconductor material; forming a first solar subcell on the substrate having a first band gap; forming a second solar subcell over the first solar subcell having a second band gap smaller than the first band gap; forming a barrier layer over the second subcell to reduce threading dislocations; forming a grading interlayer over the barrier layer, the grading interlayer having a third band gap greater than the second band gap; and forming a third solar subcell over the grading interlayer having a fourth band gap smaller than the second band gap such that the third subcell is lattice mismatched with respect to the second subcell.

A method of forming a multifunction solar cell including an upper subcell, a middle subcell, and a lower subcell, including providing first substrate for the epitaxial growth of semiconductor material; forming a first solar subcell on the substrate having a first band gap; forming a second solar subcell over the first solar subcell having a second band gap smaller than the first band gap; forming a grading interlayer over the second subcell, the grading interlayer having a third band gap greater than the second band gap; and forming a third solar subcell over the grading interlayer having a fourth band gap smaller than the second band gap such that the third subcell is lattice mismatched with respect to the second subcell, wherein at least one of the bases of a solar subcell has an exponentially doped profile.

Tunnel field-effect transistors (TFETs) are regarded as successors of metal-oxide semiconductor field-effect transistors (MOSFETs), but silicon-based TFETs typically suffer from low on-currents, a drawback related to the large resistance of the tunnel barrier. To achieve higher on-currents a nanowire-based TFET with a germanium (Ge) tunnel barrier in an otherwise silicon (Si) channel is used. A nanowire is introduced such that the lattice mismatch between silicon and germanium does not result in a highly defective interface. A dynamic power reduction as well as a static power reduction can result, compared to conventional MOSFET configurations. Multiple layers of logic can therefore be envisioned with these nanowire Si/Ge TFETs resulting in ultra-high on-chip transistor densities.

An integrated circuit structure includes a semiconductor substrate; insulation regions over the semiconductor substrate; and an epitaxy region over the semiconductor substrate and having at least a portion in a space between the insulation regions. The epitaxy region includes a III-V compound semiconductor material. The epitaxy region also includes a lower portion and an upper portion over the lower portion. The lower portion and the semiconductor substrate have a first lattice mismatch. The upper portion and the semiconductor substrate have a second lattice mismatch different from the first lattice mismatch.

A method of forming a multijunction solar cell including an upper subcell, a middle subcell, and a lower subcell, including: providing a substrate having an off-cut of 15° from the (001) plane to the (111)A plane for the epitaxial growth of semiconductor material; forming a first solar subcell on the substrate having a first band gap; forming a second solar subcell over the first solar subcell having a second band gap smaller than the first band gap; forming a grading interlayer over the second subcell layer, the grading interlayer having a third band gap greater than the second band gap; and forming a third solar subcell over the grading interlayer having a fourth band gap smaller than the second band gap such that the third subcell is lattice mismatched with respect to the second subcell.

A method of forming a multijunction solar cell including an upper subcell, a middle subcell, and a lower subcell, the method including: providing a substrate for the epitaxial growth of semiconductor material; forming a first solar subcell on the substrate having a first band gap and including a pseudomorphic window layer; forming a second solar subcell over the first solar subcell having a second band gap smaller than the first band gap; forming a graded interlayer over the second subcell, the graded interlayer having a third band gap greater than the second band gap; and forming a third solar subcell over the graded interlayer having a fourth band gap smaller than the second band gap such that the third subcell is lattice mismatched with respect to the second solar subcell.

Source and drain regions of an FET are etched by a crystallographic anisotropic etch to form a cavity surrounded by crystallographic facets. The exposure of the sidewalls of shallow trench isolation (STI) is avoided or reduced compared to the prior art. The crystallographic anisotropic etch may be combined with an isotropic etch or a recess etch to create undercuts beneath gate spacers and/or a pegging line beneath a top surface of the STI. The at least one cavity is then filled with a lattice-mismatched embedded material so that stress is applied to the channel of the FET. The resulting structure has increased containment of the embedded semiconductor region by shallow trench isolation. A reduction in stress due to the unconstrained sidewall area and an increase in the junction current due to the recessing of the pegging line are eliminated or alleviated.

A multijunction solar cell including an upper first solar subcell having a first band gap; a middle second solar subcell adjacent to the first solar subcell and having a second band gap smaller than the first band gap and having a base layer and an adjacent emitter layer, wherein the other layer adjacent to the emitter layer has an index of refraction substantially equal to that of the emitter layer; a graded interlayer adjacent to the second solar having a third band gap greater than said second band gap; and a lower solar subcell adjacent to the interlayer, and having a fourth band gap smaller than the second band gap, the third subcell being lattice mismatched with respect to the second subcell.

A multijunction solar cell includes a first photoactive subcell layer having a first-subcell lattice parameter and a composition including (a) at least one Group III element, at least one Group V element other than (nitrogen, phosphorus), and (nitrogen, phosphorus), or (b) a material selected from the group including GaInAsBi, GaInAsSb, GaInAsP, ZnGeAs₂, or BGaInAs. The multijunction solar cell also has a substrate having a substrate lattice parameter different from the first-subcell lattice parameter, and a composition-graded buffer layer between the first photoactive subcell layer and the substrate and having a buffer-layer lattice parameter graded between the first-subcell lattice parameter and the substrate lattice parameter. The substrate may be a second photoactive subcell layer having a second-subcell lattice parameter different from the first-subcell lattice parameter and sensitive to a second-photoactive-subcell-layer wavelength, and the buffer layer is transparent to the second-photoactive-subcell-layer wavelength.