Methods to introduce sub-micrometer, symmetry-breaking surface corrugation to silicon substrates to increase light trapping
Provided is a method for fabricating a nanopatterned surface. The method includes forming a mask on a substrate, patterning the substrate to include a plurality of symmetry-breaking surface corrugations, and removing the mask. The mask includes a pattern defined by mask material portions that cover first surface portions of the substrate and a plurality of mask space portions that expose second surface portions of the substrate, wherein the plurality of mask space portions are arranged in a lattice arrangement having a row and column, and the row is not oriented parallel to a [110] direction of the substrate. The patterning the substrate includes anisotropically removing portions of the substrate exposed by the plurality of spaces.
1. A negative mold for positive relief patterns, comprising: a patterned substrate comprising a surface having a plurality of symmetry-breaking surface corrugations, wherein the symmetry-breaking surface corrugations comprise a symmetry selected from at least one of C.sub.4v, C.sub.4, C.sub.2v, C.sub.2 and C.sub.1; wherein the plurality of symmetry-breaking surface corrugations comprise first ones of the plurality of symmetry-breaking surface corrugations having a first symmetry and a second ones of the plurality of symmetry-breaking surface corrugations having a second symmetry, wherein the first and second symmetries are different.
2. The mold of claim 1 , wherein the plurality of symmetry-breaking surface corrugations further comprise third ones of the plurality of the symmetry-breaking surface corrugations disposed between the first and second ones, and wherein the third ones provide a symmetry transition between the first symmetry and the second symmetry.
3. The mold of claim 1 , wherein the patterned substrate comprises c-Si.
4. An optical communication device, comprising: at least one patterned layer, the patterned layer comprising a surface having a plurality of symmetry-breaking surface corrugations, wherein the symmetry-breaking surface corrugations comprise a symmetry selected from at least one of C.sub.4v, C.sub.4, C.sub.2v, C.sub.2 and C.sub.1; wherein the plurality of symmetry-breaking surface corrugations comprise first ones of the plurality of symmetry-breaking surface corrugations having a first symmetry and a second ones of the plurality of symmetry-breaking surface corrugations having a second symmetry, wherein the first and second symmetries are different.
5. The optical communication device of claim 4 , wherein the plurality of symmetry-breaking surface corrugations further comprise third ones of the plurality of the symmetry-breaking surface corrugations disposed between the first and second ones, and wherein the third ones provide a symmetry transition between the first symmetry and the second symmetry.
6. The optical communication device of claim 4 , further comprising at least one layer disposed on the at least one patterned layer, wherein the at least one layer conforms to the symmetry-breaking surface corrugations and comprises second symmetry-breaking surface corrugations.