GeSn alloys and ordered phases with direct tunable bandgaps grown directly on silicon
View Patent ↗A method for depositing an epitaxial Ge—Sn layer on a substrate in a CVD reaction chamber includes introducing into the chamber a gaseous precursor comprising SnD4 under conditions whereby the epitaxial Ge—Sn layer is formed on the substrate. the gaseous precursor comprises SnD4 and high purity H2 of about 15-20% by volume. The gaseous precursor is introduced at a temperature in a range of about 250° C. to about 350° C. Using the process device-quality Sn—Ge materials with tunable bandgaps can be grown directly on Si substrates.
1. A semiconductor structure comprising: a substrate and a Sn x Ge 1-x layer formed directly on the substrate, wherein x has a value from about 0.02 to about 0.20, and wherein the substrate consists essentially of silicon.
2. The semiconductor structure of claim 1 wherein the Sn x Ge 1-x layer is an epitaxial layer with a direct band gap between about 0.72 eV and about 0.041 eV.
3. The semiconductor structure of claim 1 , wherein x has a value of about 0.20 and the Sn x Ge 1-x layer is a direct-gap material.
4. The semiconductor structure of claim 1 wherein the substrate consists essentially of Si(100).
5. The semiconductor structure of claim 1 wherein the substrate consists essentially of Si(111).
6. The semiconductor structure of claim 1 wherein the Sn x Ge 1-x layer has a thickness of about 50nm to about 1000nm.
7. The semiconductor structure of claim 1 further comprising a strained Ge layer formed over the Sn x Ge 1-x layer.
8. The semiconductor structure of claim 7 wherein x is greater than about 0.11 and the strained Ge layer is a direct-gap material.
9. The semiconductor structure of claim 1 , wherein the Sn x Ge 1-x layer is relaxed.
10. The semiconductor structure of claim 1 , wherein the Sn x Ge 1-x layer is epitaxial.
11. The semiconductor structure of claim 10 , wherein the substrate is accommodated by Lomer edge dislocations.
12. The semiconductor structure of claim 1 , wherein the Sn x Ge 1-x layer lattice parameters are about 5.672 Å to about 5.833 Å.
13. The semiconductor structure of claim 1 , wherein the Sn x Ge 1-x layer is atomically flat.
14. A method for depositing an epitaxial Ge—Sn layer on a substrate in a chemical vapor deposition reaction chamber, the method comprising introducing into the chamber a gaseous precursor comprising SnD 4 under conditions whereby the epitaxial Ge—Sn layer is formed on the substrate.
15. The method of claim 14 wherein the gaseous precursor comprises SnD 4 and high purity H 2 .
16. The method of claim 14 wherein the gaseous precursor further comprises high purity H 2 of about 15-20 by volume.
17. The method of claim 14 wherein the gaseous precursor is introduced at a temperature in a range of about 250° C. to about 350° C.
18. The method of claim 14 wherein the substrate comprises silicon.
19. The method of claim 14 wherein the substrate comprises Si(100).
20. The method of claim 14 wherein the Ge—Sn layer comprises Sn x Ge 1-x and x is in a range from about 0.02 to about 0.20.
21. The method of claim 14 wherein the gaseous precursor comprises SnD 4 and Ge 2 H 6 .
22. A method for depositing a strained Ge layer on a silicon substrate with a Ge—Sn buffer layer in a chemical vapor deposition reaction chamber, the method comprising introducing into the chamber a combination comprising SnD 4 and Ge 2 H 6 under conditions whereby the Ge—Sn layer is formed on the substrate and dehydrogenating Ge 2 H 6 under conditions whereby the Ge layer is formed on the Ge—Sn buffer layer.