1090results about How to "Reduce dislocation density" patented technology

There are provided a GaN field effect transistor (FET) exhibiting an excellent breakdown voltage owing to the high quality of GaN crystal in a region where the electric lines of force concentrate during operation of the same, and a method of manufacturing the same. The FET has a layer structure formed of a plurality of GaN epitaxial layers. A gate electrode and a source electrode are disposed on the surface of the layer structure, and a drain electrode is disposed on the reverse surface of the same. A region of the layer structure in which the electric lines of force concentrate during operation of the FET has a reduced dislocation density compared with the other regions in the layer structure. The GaN FET is manufactured by forming, on a crystal-growing substrate having a surface formed with a plane pattern of a material other than a GaN-based material in an identical design to a plane pattern of an electrode determining the region in which the electric lines of force concentrate, a plurality of GaN epitaxial layers, one upon another, by using the epitaxial lateral overgrowth technique, thereby forming a layer structure, and then forming operational electrodes on the surface of the layer structure.

A method for manufacturing a light-emitting diode, which includes the steps of: providing a substrate having a plurality of protruded portions on one main surface thereof wherein the protruded portion is made of a material different in type from that of the substrate and growing a first nitride-based III-V Group compound semiconductor layer on each recess portion of the substrate through a state of making a triangle in section wherein a bottom surface of the recess portion becomes a base of the triangle; laterally growing a second nitride-based III-V Group compound semiconductor layer on the substrate from the first nitride-based III-V Group compound semiconductor layer; and successively growing, on the second nitride-based III-V Group compound semiconductor layer, a third nitride-based III-V Group compound semiconductor layer of a first conduction type, an active layer, and a fourth nitride-based III-V compound semiconductor layer of a second conduction type.

A III-V nitride homoepitaxial microelectronic device structure comprising a III-V nitride homoepitaxial epi layer of improved epitaxial quality deposited on a III-V nitride material substrate, e.g., of freestanding character. Various processing techniques are described, including a method of forming a III-V nitride homoepitaxial layer on a corresponding III-V nitride material substrate, by depositing the III-V nitride homoepitaxial layer by a VPE process using Group III source material and nitrogen source material under process conditions including V/III ratio in a range of from about 1 to about 10<5>, nitrogen source material partial pressure in a range of from about 1 to about 10<3 >torr, growth temperature in a range of from about 500 to about 1250 degrees Celsius, and growth rate in a range of from about 0.1 to about 10<2 >microns per hour. The III-V nitride homoepitaxial microelectronic device structures are usefully employed in device applications such as UV LEDs, high electron mobility transistors, and the like.

Methods of crystal growth for semiconductor materials, such as nitride semiconductors, and methods of manufacturing semiconductor devices are provided. The method of crystal growth includes forming a number of island crystal regions during a first crystal growth phase and continuing growth of the island crystal regions during a second crystal growth phase while bonding of boundaries of the island crystal regions occurs. The second crystal growth phase can include a crystal growth rate that is higher than the crystal growth rate of the first crystal growth phase and/or a temperature that is lower than the first crystal growth phase. This can reduce the density of dislocations, thereby improving the performance and service life of a semiconductor device which is formed on a nitride semiconductor made in accordance with an embodiment of the present invention.

A production method of a GaN-based compound semiconductor having excellent crystallinity and a GaN-based semiconductor device produced therefrom. A discrete SiN buffer body is formed on a substrate, and a GaN buffer layer is formed thereon at low temperatures and a GaN semiconductor layer is then formed at high temperatures. By forming the discrete SiN buffer body, the crystal growth, which is dependent on the substrate, of the low-temperature buffer layer is inhibited and monocrystallization is promoted to generate seed crystals used at the time of growing the GaN buffer layer. Further, by forming SiO2 discretely between the substrate and the SiN buffer body or by forming InGaN or a superlattice layer on the GaN semiconductor layer, distortion of the GaN semiconductor layer is reduced.

A method for producing a nitride semiconductor crystal comprising a step (a) for forming fine crystal particles made of a nitride semiconductor on a substrate; a step (b) for forming a nitride semiconductor island structure having a plurality of facets inclined relative to a surface of the substrate with the fine crystal particles as nuclei; and a step (c) for causing the nitride semiconductor island structure to grow in a direction parallel with a surface of the substrate to merge a plurality of the nitride semiconductor island structures with each other, thereby forming a nitride semiconductor crystal layer having a flat surface; the steps (a)-(c) being continuously conducted in the same growing apparatus.

During the growth of a nitride semiconductor crystal on a nonpolar face nitride substrate, such as an m-face, the gas that constitutes the main flow in the process of heating up to a relatively high temperature range, before growth of the nitride semiconductor layer, (the atmosphere to which the main nitride face of the substrate is exposed) and the gas that constitutes the main flow until growth of first and second nitride semiconductor layers is completed (the atmosphere to which the main nitride face of the substrate is exposed) are primarily those that will not have an etching effect on the nitride, while no Si source is supplied at the beginning of growth of the nitride semiconductor layer. Therefore, nitrogen atoms are not desorbed from near the nitride surface of the epitaxial substrate, thus suppressing the introduction of defects into the epitaxial film. This also makes epitaxial growth possible with a surface morphology of excellent flatness.

A manufacturing method is provided for a silicon carbide semiconductor substrate adapted for reduced basal plane dislocations in a silicon carbide epitaxial layer. Between a silicon carbide epitaxial layer for device fabrication (i.e., a drift layer) and a base substrate formed of a silicon carbide single-crystal wafer, a highly efficient dislocation conversion layer through which any basal plane dislocations in the silicon carbide single-crystal wafer are converted into threading edge dislocations very efficiently when the dislocations propagate into the layer epitaxially grown is provided by epitaxial growth. Assigning to the dislocation conversion layer a donor concentration lower than that of the drift layer, therefore, allows the above conversion of a larger number of basal plane dislocations than the case where the drift layer exists alone (without the dislocation conversion layer).

To provide a semiconductor substrate of a group III nitride with a little warp, this invention provides a process comprising such steps of: epitaxial-growing a GaN layer 33 with a GaN low temperature grown buffer layer 32 upon a sapphire substrate 31; removing the sapphire substrate 31, the GaN buffer layer 32 and a small portion of the GaN layer 33 from the substrate taken out of a growth reactor to obtain a self-supporting GaN substrate 35; and after that, heat-treating the GaN substrate 35 by putting it into an electric furnace under the NH3 atmosphere at 1200° C. for 24 hours; which leads to a marked reduction of the warp of the self-supporting GaN substrate 35 such that dislocation densities of its obverse and reverse surface are 4x10<7 >cm<-2 >and 8x10<5 >cm<-2>, and thereby such a low ratio of dislocation densities of 50 is well-controlled.

The invention provides a deep-UV light-emitting diode and a preparation method thereof. A low-temperature GaN insertion layer is used to replace an AlN/AlGaN superlattice or a high-temperature GaN insertion layer to grow the deep-UV light-emitting diode. The low-temperature GaN insertion layer is a GaN with thickness of 20-50nm under the conditions of temperature being 400-900 DEG C, pressure being 30-200torr, and V/III being 1500-2500. The method can effectively lower the dislocation density in an epitaxial AlGaN layer and a quantum well, and improves the surface planeness. The prepared LED component has smooth surface, better crystal quality, starting voltage reduction, and smaller serial resistances of the component; and the electroluminescene peak value is ranged from 300nm to 370nm.

The invention provides a method which uses a graphic substrate to improve the illumination efficiency of a GaN-based efficiency, comprising the steps as follows: a silicon dioxide film is deposited on a sapphire substrate; a photoresist graphic array is optically etched; the photoresist graphic array is taken as a mask so as to etch the silicon dioxide film with the graphic structure; the silicon dioxide film with the graphic structure is taken as a mask so as to etch the sapphire substrate and the graphics is etched onto the sapphire substrate; the sapphire substrate is thoroughly cleaned so as to form a pyramid structure with triangular sections; a low-temperature nucleation layer grows on the graphic sapphire substrate; temperature is continuously increased on the low-temperature nucleation layer so as to grow an n-typed mixed GaN layer and an array structure which has low dislocation density and V-shaped holes on the surface; a multiple quantum well layer and a p-typed material layer required when the LED structure material grows continue to grow; furthermore, the final surface is led to still have the array structure with V-shaped holes.

A nitride-based semiconductor element having superior mass productivity and excellent element characteristics is obtained. This nitride-based semiconductor element comprises a substrate comprising a surface having projection portions, a mask layer formed to be in contact with only the projection portions of the surface of the substrate, a first nitride-based semiconductor layer formed on recess portions of the substrate and the mask layer and a nitride-based semiconductor element layer, formed on the first nitride-based semiconductor layer, having an element region. Thus, the first nitride-based semiconductor layer having low dislocation density is readily formed on the projection portions of the substrate and the mask layer through the mask layer serving for selective growth. When the nitride-based semiconductor element layer having the element region is grown on the first nitride-based semiconductor layer having low dislocation density, a nitride-based semiconductor element having excellent element characteristics can be readily obtained. The first nitride-based semiconductor layer is formed through only single growth on the substrate, whereby a nitride-based semiconductor element having excellent mass productivity is obtained.

The invention belongs to the technical field of semiconductor materials, and relates to a Ge/Si1-xGex super-lattice structure and preparation thereof. The high quality strain Ge/Si1-xGex super-lattice structure comprises a Si substrate, and a Si0.2Ge0.8 virtual substrate layer, a B-doped Si0.2Ge0.8 epitaxial layer, a Si0.2Ge0.8 blocking layer, a Ge/Si1-xGex super-lattice layer, a P-doped Si0.2Ge0.8 epitaxial layer, a Si0.2Ge0.8 blocking layer and a Si protective layer sequentially and epitaxially grown on the Si substrate, wherein x is more than or equal to 0.6 and less than or equal to 0.7. The epitaxial layers are sequentially grown on the Si substrate by adopting a reduced pressure chemical vapor deposition method; the obtained super-lattice structure has the properties of low dislocation defect density, low thickness and flat interface/surface, and the Ge/Si1-xGex super-lattice is in a strain state; and the super-lattice structure has high quality and is particularly suitable for manufacturing silicon-based laser devices and waveguide modulators.

A buffer layer configured of the same conductive semiconductor layers of two or more layers as a drift layer is installed by epitaxial growth between a first semiconductor layer configuring the drift layer that is a layer in which components of the semiconductor device are made and a base substrate including a silicon carbide single crystal wafer. A step of donor concentration is provided at an interface between the drift layer and the buffer layer, an interface between the semiconductor layers configuring the buffer layer, and an interface between the buffer layer and the base substrate and the donor concentration of the drift layer side is lower than that of the base substrate side, thereby making it possible to convert most basal plane dislocations into threading edge dislocations as compared to the drift layer having one layer or the buffer layer configured of one layer.

A self-supported III-V nitride semiconductor substrate having a substantially uniform carrier concentration distribution in a surface layer existing from a top surface to a depth of at least 10 μm is produced by growing a III-V nitride semiconductor crystal while forming a plurality of projections on a crystal growth interface at the initial or intermediate stage of crystal growth; conducting the crystal growth until recesses between the projections are buried, so that the crystal growth interface becomes flat; and continuing the crystal growth to a thickness of 10 μm or more while keeping the crystal growth interface flat.

A method for producing a Group III element nitride single crystal, which comprises reacting at least one Group III element selected from the group consisting of gallium(Ga), aluminum(Al) and indium(In) with nitrogen(N) in a mixed flux of sodium(Na) and at least one of an alkali metal (except Na) and an alkaline earth metal. The method allows the production, with a good yield, of the single crystal of a group III element nitride which is transparent, is reduced in the density of dislocation, has a bulk form, and is large. In particular, a gallium nitride single crystal produced by the method has high quality and takes a large and transparent bulk form, and thus has a high practical value.

The invention provides a preparation method of a polycrystalline silicon ingot. The preparation method comprises the following steps that a core source is arranged at the bottom of a crucible, and a core source layer is formed; silicon materials in a molten state are arranged on the core source layer; and the temperature in the crucible is controlled to gradually rise in a direction vertical to the upward direction form the bottom of the crucible, the temperature gradient is formed, the silicon materials in the molten state form core crystallization by utilizing the core source, and the polycrystalline silicon ingot is prepared. The invention also provides high-quality polycrystalline silicon ingot obtained by the preparation method, a polycrystalline silicon slice obtained through the preparation of the polycrystalline silicon ingot and the crucible for polycrystalline silicon ingot casting. The polycrystalline silicon ingot prepared by the preparation method has the advantages that the crystalline size is uniform and regular, the dislocation density is low, and in addition, no obvious pine-tree crystals or twin crystals exist.

A production method is provided in which Group-III-element nitride single crystals that have a lower dislocation density and a uniform thickness and are transparent, high quality, large, and bulk crystals can be produced with a high yield. The method for producing Group-III-element nitride single crystals includes: heating a reaction vessel containing at least one metal element selected from the group consisting of an alkali metal and an alkaline-earth metal and at least one Group III element selected from the group consisting of gallium (Ga), aluminum (Al), and indium (In) to prepare a flux of the metal element; and feeding nitrogen-containing gas into the reaction vessel and thereby allowing the Group III element and nitrogen to react with each other in the flux to grow Group-III-element nitride single crystals, wherein the single crystals are grown, with the flux being stirred by rocking the reaction vessel, for instance.

A III-V group nitride system semiconductor self-standing substrate has: a first III-V group nitride system semiconductor crystal layer that has a region with dislocation lines gathered densely, the dislocation lines being gathered substantially perpendicular to a surface of the substrate, and a region with dislocation lines gathered thinly; and a second III-V group nitride system semiconductor crystal layer that is formed up to 10 μm from the surface of the substrate on the first III-V group nitride system semiconductor crystal layer and that has a dislocation density distribution that is substantially uniform.