A crystal substrate 1 includes an underlying layer 2 and a thick film 3. The underlying layer 2 is composed of a crystal of a nitride of a group 13 element and includes a first main face 2a and a second main face 2b. The thick film 3 is composed of a crystal of a nitride of a group 13 element and provided over the first main face of the underlying layer. The underlying layer 2 includes a low carrier concentration region 5 and a high carrier concentration region 4 both extending between the first main face 2a and the second main face 2b.

This invention provides a paste composition that enables a silicon germanium layer to be formed safely and easily, and a method for forming a silicon germanium layer safely and easily. The present invention provides a paste composition for forming a silicon germanium layer, the composition comprising aluminum and germanium, wherein the content of the germanium is more than 1 part by mass and 10000 parts by mass or less, per 100 parts by mass of the aluminum.

A crystal substrate 1 includes an underlying layer 2 and a thick film 3. The underlying layer 2 is composed of a crystal of a nitride of a group 13 element and includes a first main face 2a and a second main face 2b. The thick film 3 is composed of a crystal of a nitride of a group 13 element and provided over the first main face of the underlying layer. The underlying layer 2 includes a low carrier concentration region 5 and a high carrier concentration region 4 both extending between the first main face 2a and the second main face 2b. The low carrier concentration region 5 has a carrier concentration of 10.sup.17/cm.sup.3 or lower and a defect density of 10.sup.7/cm.sup.2 or lower. The high carrier concentration region 4 has a carrier concentration of 10.sup.19/cm.sup.3 or higher and a defect density of 10.sup.8/cm.sup.2 or higher. The thick film 3 has a carrier concentration of 10.sup.18/cm.sup.3 or higher and 10.sup.19/cm.sup.3 or lower and a defect density of 10.sup.7/cm.sup.2 or lower.

A composition of matter comprising a plurality of nanowires on a substrate, said nanowires having been grown epitaxially on said substrate in the presence of a metal catalyst such that a catalyst deposit is located at the top of at least some of said nanowires, wherein said nanowires comprise at least one group III-V compound or at least one group II-VI compound or comprises at least one non carbon group IV element; and wherein a graphitic layer is in contact with at least some of the catalyst deposits on top of said nanowires.

A crystal substrate 1 includes an underlying layer 2 and a thick film 3. The underlying layer 2 is composed of a crystal of a nitride of a group 13 element and includes a first main face 2a and a second main face 2b. The thick film 3 is composed of a crystal of a nitride of a group 13 element and provided over the first main face of the underlying layer. The underlying layer 2 includes a low carrier concentration region 5 and a high carrier concentration region 4 both extending between the first main face 2a and the second main face 2b. The low carrier concentration region 5 has a carrier concentration of 10.sup.17/cm.sup.3 or lower and a defect density of 10.sup.7/cm.sup.2 or lower. The high carrier concentration region 4 has a carrier concentration of 10.sup.19/cm.sup.3 or higher and a defect density of 10.sup.8/cm.sup.2 or higher. The thick film 3 has a carrier concentration of 10.sup.18/cm.sup.3 or higher and 10.sup.19/cm.sup.3 or lower and a defect density of 10.sup.7/cm.sup.2 or lower.

Doped semiconductor ink formulations, methods of making doped semiconductor ink formulations, methods of coating or printing thin films, methods of forming electronic devices and/or structures from the thin films, and methods for modifying and controlling the threshold voltage of a thin film transistor using the films are disclosed. A desired dopant may be added to an ink formulation comprising a Group IVA compound and a solvent, and then the ink may be printed on a substrate to form thin films and conductive structures/devices, such as thin film transistors. By adding a customized amount of the dopant to the ink prior to printing, the threshold voltage of a thin film transistor made from the doped semiconductor ink may be independently controlled upon activation of the dopant.