López-Fraguas, E.; Binkowski, F.; Burger, S.; Hagedorn, S.; García-Cámara, B.; Vergaz, R.; Becker, C.; Manley, P.: Tripling the light extraction efficiency of a deep ultraviolet LED using a nanostructured p-contact. Scientific Reports 12 (2022), p. 11480/1-11
10.1038/s41598-022-15499-7
Open Access Version
Abstract:
Despite a wide array of applications, deep ultra‑violet light emitting diodes offer relatively poor efficiencies compared to their optical counterparts. A contributing factor is the lower light extraction efficiency due to both highly absorbing p‑contacts and total internal reflection. Here, we propose a structure consisting of a hexagonal periodic array of cylindrical nanoholes in the multi‑layered p‑contact which are filled with platinum. This nanostructure reduces the absorption of the p‑contact layer, leading to a higher emission into the n‑contact compared to a planar reference. An optimum geometry of the nanostructure allows a light extraction efficiency of 15.0%, much higher than the typical 4.6% of a planar reference. While the nanostructure strongly decreases the light absorption in the p‑contact, it is still not able to considerably reduce the total internal reflection. Consequently, the nanostructured p‑contact should be combined with other optical strategies, such as nanopatterned sapphire substrates to increase the efficiency even further. Despite this, the nanostructure described in this work provides a readily realizable path to enhancing the light extraction efficiency of state‑of‑ the‑art deep ultra‑violet light emitting diodes.