Field effect devices having short period superlattice structures using Si and Ge
First Claim
1. A field effect device comprisinga monocrystalline silicon semiconductor substrate,a first epitaxial layer of silicon grown on said substrate and doped with a first conductivity type dopant,a plurality of layers of semiconductor material epitaxially grown on said first epitaxial layer, said plurality of layers comprising alternate single layers of silicon and of germanium semiconductor materials, thereby forming a plurality of heterojunctions in a superlattice structure,a source and a drain formed in spaced apart regions in said first epitaxial layer with said superlattice structure therebetween, anda gate contact formed over said superlattice structure.
1 Assignment
0 Petitions
Accused Products
Abstract
Carrier mobility in a heterojunction field effect device is increased by reducing or eliminating alloy scattering. The active channel region of the field effect device uses alternating layers of pure silicon and germanium which form a short period superlattice with the thickness of each layer in the superlattice being no greater than the critical thickness for maintaining a strained heterojunction. The gate contact of the field effect device can comprise quantum Si/Ge wires which provide quantum confinement in the growth plane, thereby allowing the field effect device to further improve the mobility by restricting phonon scattering. The structure can be used to improve device speed performance.
-
Citations
20 Claims
-
1. A field effect device comprising
a monocrystalline silicon semiconductor substrate, a first epitaxial layer of silicon grown on said substrate and doped with a first conductivity type dopant, a plurality of layers of semiconductor material epitaxially grown on said first epitaxial layer, said plurality of layers comprising alternate single layers of silicon and of germanium semiconductor materials, thereby forming a plurality of heterojunctions in a superlattice structure, a source and a drain formed in spaced apart regions in said first epitaxial layer with said superlattice structure therebetween, and a gate contact formed over said superlattice structure.
- 5. The field effect device as defined by claim 5 wherein numbers of atomic layers for silicon and germanium are n and m and the ratio of n to m+n equals alloy concentration of the buffer layer whereby said superlattice has no average strain with respect to said buffer layer.
-
11. A field effect device comprising
a monocrystalline silicon semiconductor substrate, a first epitaxial layer of silicon-germanium alloy grown on said substrate and doped with a first conductivity type dopant, a plurality of layers of semiconductor material epitaxially grown on said first epitaxial layer said plurality of layers comprising alternate single layers of silicon and of germanium semiconductor materials, thereby forming a plurality of heterojunctions in a superlattice structure, a source and a drain formed in spaced apart regions in said first epitaxial layer with said superlattice structure therebetween, and a gate contact formed over said superlattice structure.
Specification