Method for producing a freestanding and stress-free epitaxial layer starting from a disposable substrate patterened in etched pillar array

Method for producing a freestanding epitaxial layer starting from a substrate that can be disposed,

• wherein the epitaxial layer is made of a first semiconductor material,
• wherein the substrate is made of a second semiconductor material,
• wherein the first semiconductor material is different from the second semiconductor material, wherein the CTE of the first semiconductor material is different from the CTE of the second semiconductor material,
• comprising the steps of:
• A) patterning said substrate by an etching process so to form an array of pillars, said pillars being laterally spaced from each other and having a top section larger than a bottom section and intermediate sections,
• B) depositing said second semiconductor material on top of said pillars at a growth temperature so to form an epitaxial layer generated by vertical and lateral growth of said second semiconductor material, and
• C) inducing breaking of said pillars by cooling said substrate and said epitaxial layer below said growth temperature.