A method of fabricating semiconductor devices, such as GaN LEDs, on insulating substrates, such as sapphire. Semiconductor layers are produced on the insulating substrate using normal techniques. Trenches that define the boundaries of the individual devices are formed through the semiconductor layers and into the insulating substrate, beneficially by inductive coupled plasma reactive ion etching. A first support structure is attached to the semiconductor layers. The hard substrate is then removed, beneficially by laser lift off. A second supporting structure, preferably conductive, is substituted for the hard substrate and the first supporting structure is removed. Individual devices are then diced, beneficially by etching through the second supporting structure. A protective photo-resist layer can protect the semiconductor layers from the attachment of the first support structure. A conductive bottom contact (possibly reflective) can be inserted between the second supporting structure and the semiconductor layers.