Semiconductor heterostructure devices with strained semiconductor layers
AssigneeAT&T Corp.
InventorsDaniel Brasen, Eugene A. Fitzgerald, Jr., Martin L. Green, Donald P. Monroe, Paul J. Silverman, Ya-Hong Xie
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Abstract
A heterostructure includes a stained epitaxial layer of either silicon or germanium that is located overlying a silicon substrate, with a spatially graded Ge.sub.x Si.sub.1-x epitaxial layer overlain by a ungraded Ge.sub.x.sbsb.0 Si.sub.1-x.sbsb.0 intervening between the silicon substrate and the strained layer. Such a heterostructure can serve as a foundation for such devices as surface emitting LEDs, either n-channel or p-channel silicon-based MODFETs, and either n-channel or p-channel silicon-based MOSFETs.
Claims23
A heterostructure comprising
- (a) a monocrystalline silicon substrate;
- (b) a spatially graded epitaxial layer of germanium-silicon located on the silicon substrate and forming an interface therewith, the spatially graded epitaxial layer having a spatial gradient of germanium that is less than about 25 percent per micrometer, and the spatially graded epitaxial layer having a concentration of germanium that is equal to approximately zero at the interface;
- (c) a first spatially ungraded epitaxial layer of germanium-silicon located on the spatially graded epitaxial layer;
- (d) an epitaxial layer of germanium or silicon located on the first spatially ungraded epitaxial layer of germanium-silicon;
- (e) a second spatially ungraded epitaxial layer of germanium-silicon located on the epitaxial layer of germanium or silicon.
A MODFET device comprising
- a monocrystalline silicon substrate;
- a spatially graded epitaxial layer of germanium-silicon located on the silicon substrate and forming an interface therewith, the spatially graded epitaxial layer having a spatial gradient of germanium that is less than about 25 percent per micrometer, and the spatially graded epitaxial layer having a concentration of germanium that is equal to approximately zero at the interface;
- a first layer of germanium-silicon alloy located on said spatially graded epitaxial layer and having a germanium concentration in the range between 10 percent and 50 percent;
- a layer of strained silicon epitaxially grown on said first layer of alloy;
- a second layer of germanium-silicon alloy epitaxially grown on said strained silicon layer, said second layer including a pair of spaced apart contact regions for electrically contacting said silicon layer;
- source and drain ohmic contacts means disposed on said second layer of alloy for contacting said contact regions,
- Schottky barrier contact means disposed between said source and drain contact means, whereby conduction between said source and drain is enhanced by application of a negative voltage to said Schottky contact.
A device comprising:
- a monocrystalline silicon substrate;
- a spatially graded expitaxial layer of germanium-silicon located on the silicon substrate and forming an interface therewith, the spatially graded epitaxial layer having a spatial gradient of germanium that is less than about 25 percent per micrometer, and the spatially graded epitaxial layer having a concentration of germanium that is equal to approximately zero at the interface;
- a layer of germanium-silicon alloy Ge.sub.x Si.sub.1-x (0.10.ltoreq.x.ltoreq.0.50) located on said spatially graded epitaxial layer and having a threading dislocation density of less than 5.times.10.sup.6 cm.sup.-2 ;
- a strained layer of silicon epitaxially grown on said layer of alloy;
- a second layer of germanium-silicon alloy epitaxially grown on said strained layer of silicon;
- and
- first and second spaced-apart impurity-doped regions located in said strained silicon layer.
Dependencies are inferred from the claim text.