Semiconductor process

A method of making a photonic band gap material, the method comprising:

• (a) growing an epitaxial layer of a first semiconductor material onto a substrate;
• (b) applying a mask to selected areas of the first semiconductor material and etching away the non-masked areas of the first semiconductor material to form a plurality of recesses;
• (c) selectively growing an epitaxial layer of a second semiconductor material, while the mask applied in step (b) is still in place, to fill the plurality of recesses created by the etching of the first semiconductor material;
• (d) removing the mask and subsequently growing a further epitaxial layer of the first semiconductor material over the first semiconductor material and the second semiconductor material;
• (e) applying a mask to selected areas of the further epitaxial layer of the first semiconductor material and etching away the non-masked areas of the further epitaxial layer of the first semiconductor material to form a further plurality of recesses, said further plurality of recesses being rotationally displaced with respect to the plurality of recesses formed within the preceding layer of the first semiconductor material;
• (f) selectively growing a epitaxial layer of the second semiconductor material, to fill the recesses created by the etching of the first semiconductor material;
• and
• (g) repeating steps (d), (e), and (f) as required to form a semiconductor product having a plurality of layers of interleaved regions of the first semiconductor material and the second semiconductor material, the regions in each of the layers being rotationally displaced with respect to the regions inn the adjacent layers for producing photonic band gap material.