Semiconductor nanostructures, semiconductor devices, and methods of making same
A semiconductor structure is provided, which includes multiple sections arranged along a longitudinal axis. Preferably, the semiconductor structure comprises a middle section and two terminal sections located at opposite ends of the middle section. A semiconductor core having a first dopant concentration preferably extends along the longitudinal axis through the middle section and the two terminal sections. A semiconductor shell having a second, higher dopant concentration preferably encircles a portion of the semiconductor core at the two terminal sections, but not at the middle section, of the semiconductor structure. It is particularly preferred that the semiconductor structure is a nanostructure having a cross-sectional dimension of not more than 100 nm.
1. A method comprising:
forming a semiconductor structure having a longitudinal axis, wherein a semiconductor core having a first dopant concentration extends along the longitudinal axis, and wherein a semiconductor shell having a second, higher dopant concentration also extends along the longitudinal axis and encircles the semiconductor core; and
selectively removing a portion of the semiconductor shell from at least one section of the semiconductor structure, so that a remaining portion of the semiconductor shell encircles a portion of the semiconductor core at other sections, but not said at least one section, of the semiconductor structure, wherein the portion of the semiconductor shell is removed from a middle section of the semiconductor structure, so that the remaining portion of the semiconductor shell encircles a portion of the semiconductor core at two terminal sections at opposite ends of the middle section, but not at the middle section of the semiconductor structure.
2. The method of claim 1 , wherein the semiconductor structure is a nanostructure having a cross-sectional dimension of not more than about 100 nm.
3. The method of claim 1 , wherein both the semiconductor core and the semiconductor shell comprise the same semiconductor material.
4. The method of claim 3 , wherein the semiconductor core is undoped, wherein the semiconductor shell is doped with an n-type dopant.
5. The method of claim 3 , wherein the semiconductor core is undoped, wherein the semiconductor shell is doped with a p-type dopant.
6. The method of claim 3 , wherein both the semiconductor core and the semiconductor shell are doped with an n-type dopant, wherein the first dopant concentration ranges from about 10 11 to about 10 17 atoms/cm 3 , and wherein the second, higher dopant concentration ranges from about 10 17 to about 10 21 atoms/cm 3 .
7. The method of claim 3 , wherein both the semiconductor core and the semiconductor shell are doped with a p-type dopant, wherein the first dopant concentration ranges from about 10 11 to about 10 17 atoms/cm 3 , and wherein the second, higher dopant concentration ranges from about 10 17 to about 10 21 atoms/cm 3 .
8. A method comprising:
forming a semiconductor structure having a longitudinal axis, wherein a semiconductor core having a first dopant concentration extends along the longitudinal axis, and wherein a semiconductor shell having a second, higher dopant concentration also extends along the longitudinal axis and encircles the semiconductor core; and
selectively removing a portion of the semiconductor shell from at least one section of the semiconductor structure, so that a remaining portion of the semiconductor shell encircles a portion of the semiconductor core at other sections, but not said at least one section, of the semiconductor structure, wherein said selectively removing comprises:
forming a patterned mask layer to selectively cover the other sections, but not said at least one section, of the semiconductor structure, wherein the portion of the semiconductor shell to be selectively removed is exposed at said at least one section of the semiconductor structure;
oxidizing the exposed portion of the semiconductor shell to form a semiconductor oxide at said at least one section of the semiconductor structure; and
selectively etching the semiconductor oxide.
9. The method of claim 8 , further comprising repeating the oxidizing and selective etching steps until the exposed portion of the semiconductor shell is completely removed to expose an underlying portion of the semiconductor core at said at least one section of the semiconductor structure.
10. The method of claim 8 , wherein the semiconductor structure is a nanostructure having a cross-sectional dimension of not more than about 100 nm.
11. The method of claim 8 , wherein both the semiconductor core and the semiconductor shell comprise the same semiconductor material.
12. The method of claim 11 , wherein the semiconductor core is undoped, wherein the semiconductor shell is doped with an n-type dopant.
13. The method of claim 11 , wherein the semiconductor core is undoped, wherein the semiconductor shell is doped with a p-type dopant.
14. The method of claim 11 , wherein both the semiconductor core and the semiconductor shell are doped with an n-type dopant, wherein the first dopant concentration ranges from about 10 11 to about 10 17 atoms/cm 3 , and wherein the second, higher dopant concentration ranges from about 10 17 to about 10 21 atoms/cm 3 .
15. The method of claim 11 , wherein both the semiconductor core and the semiconductor shell are doped with a p-type dopant, wherein the first dopant concentration ranges from about 10 11 to about 10 17 atoms/cm 3 , and wherein the second, higher dopant concentration ranges from about 10 17 to about 10 21 atoms/cm 3 .