Low temperature epitaxial growth of quaternary wide bandgap semiconductors
A method of growing quaternary epitaxial films having the formula YCZN wherein Y is a Group IV element and Z is a Group III element at temperatures in the range 550-750° C. is provided. In the method, a gaseous flux of precursor H 3 YCN and a vapor flux of Z atoms are introduced into a gas-source molecular beam epitaxial (GSMBE) chamber where they combine to form thin film of YCZN on the substrate. Preferred substrates are silicon, silicon carbide and AlN/silicon structures. Epitaxial thin film SiCAlN and GeCAlN are provided. Bandgap engineering may be achieved by the method by adjusting reaction parameters of the GSMBE process and the relative concentrations of the constituents of the quaternary alloy films. Semiconductor devices produced by the present method have bandgaps from about 2 eV to about 6 eV and exhibit a spectral range from visible to ultraviolet which makes them useful for a variety of optoelectronic and microelectronic applications. Large-area substrates for growth of conventional Group III nitrides and compounds are produced by SiCAlN deposited on large-diameter silicon wafers. The quaternary compounds, especially the boron containing compounds, exhibit extreme hardness. These quaternary compounds are radiation resistant and may be used in space exploration.
1. A method for depositing an epitaxial thin film having the quaternary formula YCZN wherein Y is a Group IV element and Z is a Group III element on a substrate at temperature between ambient temperature and 1000° C. in a gas source molecular beam epitaxial chamber, comprising introducing into said chamber:
i. gaseous flux of precursor H 3 YCN wherein H is hydrogen or deuterium; and
ii. vapor flux of Z atoms; under conditions whereby said precursor and said Z atoms combine to form epitaxial YCZN on said substrate.
2. The method of claim 1 wherein said temperature is about 550° C. to 750° C.
3. The method of claim 1 wherein said substrate is silicon or silicon carbide.
4. The method of claim 3 wherein said substrate is Si(111) or α-SiC(0001).
5. The method of claim 4 wherein said substrate is α-SiC(0001) comprising the additional step of cleaning said substrate prior to deposition of said quaternary film.
6. The method of claim 5 wherein said cleaning step comprises hydrogen etching.
7. The method of claim 3 wherein said substrate is a large-diameter silicon wafer.
8. The method of claim 7 wherein said silicon wafer comprises Si(111).
9. The method of claim 1 wherein said substrate is Si(111) comprising a buffer layer, and said epitaxial YCZN is deposited on said buffer layer.
10. The method of claim 9 wherein said buffer layer is a Group III nitride.
11. The method of claim 10 wherein said buffer layer is AlN.
12. The method of claim 1 wherein Y is silicon, germanium or tin.
13. The method of claim 1 wherein Z is aluminum, gallium or indium.
14. The method of claim 1 wherein Z is boron.
15. The method of claim 1 for depositing thin film YCZN wherein Y is silicon and said precursor is H 3 SiCN.
16. The method of claim 1 for depositing the thin film YCZN wherein Y is germanium and said precursor is H 3 GeCN.
17. The method of claim 1 for depositing epitaxial thin film SiCZN on a substrate wherein said precursor is H 3 SiCN, said Z atom is aluminum and said substrate is Si(111) or α-SiC(0001).
18. The method of claim 1 for depositing epitaxial thin film GeCZN on a substrate wherein said precursor is D 3 GeCN, said Z atom is aluminum and said substrate is Si(111) or α-SiC(0001).
19. The method of claim 1 for depositing epitaxial thin film having the formula (YC) (0.5−x) (ZN) (0.5+x) wherein x is chosen to be a value 0<x≦0.5, and Z is the same or different in each occurrence, comprising in addition the step of introducing into said chamber a flux of nitrogen atoms and maintaining the flux of said precursor, said nitrogen atoms and said Z atoms at a ratio selected to produce quaternary semiconductors having said chosen value of x.