Method of fabricating an optoelectronic device with a hollow component in epitaxial layer

A method of fabricating an epitaxial device, comprising:

• providing a substrate having a first surface and a normal direction;
• epitaxially forming a first transition layer in a first temperature on the first surface of the substrate and in-situ incorporating a porogen into the first transition layer;
• adjusting the first temperature to a second temperature to burn out the porogen from the first transition layer;
• providing an epitaxial layer on the first transition layer;
• and
• removing the substrate from the epitaxial layer, wherein a hollow component is formed inside the first transition layer after burning out the porogen, wherein the porogen is a cyclic structure.