Transferable thin‑film GaN LEDs

Electrochemical etching lifts membranes of III‑nitride LEDs, opening the door to scalable integration into CMOS-based photonics.

BY MIKOŁAJ CHLIPAŁA AND HENRYK TURSKI FROM THE INSTITUTE OF HIGH PRESSURE PHYSICS OF THE POLISH ACADEMY OF SCIENCES

Generation of visible light has been transformed by GaN. From solid‑state lighting to backlighting displays, optical communication and sensing, GaN‑based devices are deeply embedded in today’s technology. Yet as optoelectronic systems become more complex, another key requirement is coming sharply into focus: the ability to integrate high‑quality light sources onto CMOS-compatible substrates.

This particular task is far from trivial. The trait that ensures the success of GaN devices – their excellent quality when grown on native bulk GaN substrates – has a downside, as it makes them stubbornly difficult to integrate with other technologies. And as well as being technically demanding, GaN substrates are expensive, reinforcing the need to use the material as efficiently as possible.

Moreover, bulk GaN is poorly suited for integration with with photonic integrated circuits, silicon electronics and flexible electronic platforms. All three of these technologies demand substrates that are inexpensive, available in large sizes and supported by mature fabrication ecosystems – criteria that bulk GaN fails to fulfil. And one potential solution, substrate re-use, is not easy. For GaN devices grown homoepitaxially on bulk substrates, it’s been a formidable challenge to detach the active device without damaging it.