Semiconductor device and method of making same
First Claim
1. A semiconductor device deposited on a surface suitable for epitaxial growth having a first lattice constant and a first thermal evaporation rate manufactured by a method comprising the steps of:
- a) depositing a lattice-mismatched layer, having a second lattice constant in no-strain state, which is different of the lattice constant of the surface, wherein the lattice-mismatched layer has a second thermal evaporation rate, wherein the lattice-mismatched layer is deposited until at least one dislocation in the lattice-mismatched layer is created and a desired thickness is reached;
b) depositing a cap layer, having a third lattice constant and a third thermal evaporation rate wherein the third thermal evaporation rate is lower than the second evaporation rate, such that the cap layer nucleates selectively on at least one region of the lattice-mismatched layer such that the at least one dislocation is not covered by the cap layer; and
c) annealing the device at a temperature and duration, such that the at least one dislocation is eliminated by local evaporation of the nearby region of the lattice-mismatched layer.
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Abstract
The method produces coherent dislocation-free regions from initially dislocated and/or defect-rich lattice mismatched layer grown on top of the substrate having a different lattice constant, which does not contain any processing steps before of after the lattice-mismatched layer growth. The process preferably uses in situ formation of a cap layer on top of a dislocated layer. The cap layer preferably has a lattice parameter close to that in the underlying substrate, and different from that in the lattice mismatched layer in no strain state. Under these conditions, the cap layer undergoes elastic repulsion from the regions in the vicinity of the dislocations, where the lattice parameter is the most different from that in the substrate. The cap layer is absent in these regions. When the cap layer has a lower thermal evaporation rate than the underlying lattice-mismatched layer, the regions of this lattice-mismatched layer containing dislocations are selectively evaporated at high enough temperatures, and only the coherent defect-free regions of the initially defect-rich lattice-mismatched layer remain on the substrate. In one embodiment of the invention, the defect-free regions are formed on the substrate with a size preferably tuned in the range of 30-1000 nm, depending on the annealing conditions, thickness of the cap layer, and the lattice mismatch. A device created by this method is also disclosed.
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Citations
10 Claims
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1. A semiconductor device deposited on a surface suitable for epitaxial growth having a first lattice constant and a first thermal evaporation rate manufactured by a method comprising the steps of:
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a) depositing a lattice-mismatched layer, having a second lattice constant in no-strain state, which is different of the lattice constant of the surface, wherein the lattice-mismatched layer has a second thermal evaporation rate, wherein the lattice-mismatched layer is deposited until at least one dislocation in the lattice-mismatched layer is created and a desired thickness is reached;
b) depositing a cap layer, having a third lattice constant and a third thermal evaporation rate wherein the third thermal evaporation rate is lower than the second evaporation rate, such that the cap layer nucleates selectively on at least one region of the lattice-mismatched layer such that the at least one dislocation is not covered by the cap layer; and
c) annealing the device at a temperature and duration, such that the at least one dislocation is eliminated by local evaporation of the nearby region of the lattice-mismatched layer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification