Engineered substrates, free-standing semiconductor microstructures, and related systems and methods

A free-standing microstructure comprising:

• a first silicon layer;
• a second silicon layer comprising a monocrystalline silicon film;
• and
• an intermediate layer between the first silicon layer and the second silicon layer,
• wherein the intermediate layer comprises a material of the intermediate layer consisting essentially of silicon and germanium and includes monocrystalline silicon-germanium (Si1-xGex),
• wherein the material of the intermediate layer is relaxed and substantially free of residual strain;
• wherein the intermediate layer is formed in multiple layers, and
• wherein a dislocation density decreases in successive layers of said multiple layers;
• and
• one or more voids defined by absence of a material between the first silicon layer and the second silicon layer.

A method of forming a free-standing microstructure, the method comprising:

• forming an engineered substrate by at least:
• growing an intermediate layer over a silicon substrate, a material of the intermediate layer consisting essentially of silicon and germanium, wherein the intermediate layer is grown in multiple layers and wherein a dislocation density decreases in successive layers of said multiple layers;
• growing a monocrystalline silicon film over the material of the intermediate layer;
• forming an opening through the monocrystalline silicon film;
• and
• removing at least a portion of the material of the intermediate layer from between the monocrystalline silicon film and the silicon substrate to form one or more voids.