Method for forming low defect density alloy graded layers and structure containing such layers
AssigneeMassachusetts Institute of Technology
InventorsDavid Michael Isaacson, Eugene A. Fitzgerald
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Abstract
A structure and method of forming same, comprising a low threading density alloy graded layer, deposited according to a deposition temperature profile in correspondence with increasing alloy composition. In one embodiment, a first substantially relaxed alloy graded layer is deposited while varying a deposition temperature according to a first temperature profile. A second substantially relaxed alloy graded layer is deposited over the first graded layer while varying a deposition temperature according to a second temperature profile. Preferably, the minimum signed rate of change of the second temperature profile is less than the maximum signed rate of change of the first temperature profile.
Claims17
A method of forming a semiconductor structure, comprising:
- depositing a first structure over a substrate, wherein the entire first structure is deposited at a temperature greater than about 700° C., wherein the first structure comprises a substantially relaxed silicon germanium graded layer having a surface comprising a germanium content greater than about 92% by composition;
- and
- depositing a second structure over the first structure, at a temperature less than about 700° C., wherein the second structure comprises a semiconductor having a germanium content greater than about 92% by composition.
Dependencies are inferred from the claim text.