Superconducting LED

Purpose and goal

We aimed to make nanowire based LEDs with superconducting leads that emit entangled photons. The project had three main components: developing the technique for fabrication, optically characterizing the LED, and developing efficient single photon detectors for the mid-IR. We have completed the goal of fabricating nanowire devices that support superconductivity, and we have developed single photon detectors for wavelengths up to 4 microns. Work is ongoing with fabricating LEDs from the nanowires and to measure their optical emission.

Expected results and effects

Nanowire Josephson junction devices were fabricated showing superconducting critical currents of a few hundred nano-Amps. The devices degraded quickly. Currently we are working on a way to keep them stable. The fabrication yield is still very low and improvements to the recipe is needed. We expect to reach the remaining goals within the next two years. Though a SLED has not yet been fabricated, the optical setup that was built contributed to one publication on quantum dots as well as work on other projects where publication is being prepared.

Planned approach and implementation

It is critical to have multiple sources of nanowires. Even though building the measurement setup and developing detectors were completed on or ahead of schedule, the lack of material delayed the project. The transfer of processing recipe to KTH also took longer than anticipated. This is partly due to an upgrade to the lithography system here at KTH, which caused short-term delays but should make future work much more efficient. More deliverables should have been included that did not rely on the proximity effect, such as the measurement of mid-IR LED.