An epitaxial structure includes a substrate, a first epitaxial layer and a second epitaxial layer. The substrate has a surface, and the first epitaxial layer is disposed over the substrate and defines a plurality of stepped air voids and an opening over each of the stepped air voids. The second epitaxial layer is disposed on the first epitaxial layer and collectively defines the stepped air voids with the surface and the first epitaxial layer.

An epitaxial structure includes a substrate, a first epitaxial layer and a second epitaxial layer. The substrate has a surface, and the first epitaxial layer is disposed over the substrate and defines a plurality of stepped air voids and an opening over each of the stepped air voids. The second epitaxial layer is disposed on the first epitaxial layer and collectively defines the stepped air voids with the surface and the first epitaxial layer.

A method for manufacturing a semiconductor wafer according to the invention of the present application includes a first step of forming a gallium nitride growth layer which is divided into a plurality of small sections, on an upper surface of a silicon substrate and a second step of filling portions between the plurality of small sections with an insulating film, wherein the insulating film exerts stress to the silicon substrate in a direction opposite to a direction in which the gallium nitride growth layer exerts stress on the silicon substrate.

A method for manufacturing a semiconductor wafer according to the invention of the present application includes a first step of forming a gallium nitride growth layer which is divided into a plurality of small sections, on an upper surface of a silicon substrate and a second step of filling portions between the plurality of small sections with an insulating film, wherein the insulating film exerts stress to the silicon substrate in a direction opposite to a direction in which the gallium nitride growth layer exerts stress on the silicon substrate.

A method for making an epitaxial structure includes the following steps. A substrate having an epitaxial growth surface is provided. A buffer layer is formed on the epitaxial growth surface. A carbon nanotube layer is placed on the buffer layer. A first epitaxial layer is epitaxially grown on the buffer layer. The substrate and the buffer layer are removed to expose a second epitaxial growth surface. A second epitaxial layer is epitaxially grown on the second epitaxial growth surface.

A method for making an epitaxial structure includes the following steps. A substrate having an epitaxial growth surface is provided. A buffer layer is formed on the epitaxial growth surface. A carbon nanotube layer is placed on the buffer layer. A first epitaxial layer is epitaxially grown on the buffer layer. The substrate and the buffer layer are removed to expose a second epitaxial growth surface. A second epitaxial layer is epitaxially grown on the second epitaxial growth surface.

Disclosed are methods and mask structures for epitaxially growing substantially defect-free semiconductor material. In some embodiments, mask structure includes a first level defining a first trench extending through the first level, wherein a bottom of the first trench is defined by a semiconductor substrate, and a second level on top of the first level, wherein the second level defines a plurality of second trenches positioned at a non-zero angle with respect to the first trench.

Disclosed are methods and mask structures for epitaxially growing substantially defect-free semiconductor material. In some embodiments, mask structure includes a first level defining a first trench extending through the first level, wherein a bottom of the first trench is defined by a semiconductor substrate, and a second level on top of the first level, wherein the second level defines a plurality of second trenches positioned at a non-zero angle with respect to the first trench.

A heteroepitaxially grown structure includes a substrate and a mask including a high aspect ratio trench formed on the substrate. A cavity is formed in the substrate having a shape with one or more surfaces and including a resistive neck region at an opening to the trench. A heteroepitaxially grown material is formed on the substrate and includes a first region in or near the cavity and a second region outside the first region wherein the second region contains fewer defects than the first region.

An object of the present invention is to provide a novel technique capable of manufacturing a large-diameter semiconductor substrate. The present invention is a method for manufacturing a semiconductor substrate including a crystal growth step S30 of forming a growth layer 20 on an underlying substrate 10 having through holes 11. In addition, the present invention is a method for forming a growth layer 20 including the through hole formation step S10 of forming through holes 11 in the underlying substrate 10 before forming the growth layer 20 on a surface of the underlying substrate 10.