A new material for the electron-blocking layer of photonic devices

LEDs consist of a p-n junction formed by a p-type semiconductor and an n-type semiconductor. Under forward operation, holes from the p-type layer and the electrons from the n-type layer are injected into quantum wells, where they recombine and emit photons. The electron blocking layers (EBLs) prevent the overflow of electrons from quantum wells into the p-region but allow for the holes to pass through, thus increasing light output.

Lonergan et al. recognized the potential for inserting aluminum scandium nitride (AlScN) as an EBL of blue LEDs. AlScN can be lattice-matched and grown in compatible conditions to gallium nitride (GaN), a central component of blue LEDs, thereby reducing defects caused by strain; favorable band offsets for hole injection are also achievable. Despite these qualities, so far AlScN has not been integrated into light-emitting devices.

The authors tested this potential by comparing the performance of a blue LED containing an AlScN EBL with one without an EBL. They found that while the AlScN EBL blue LED effectively reduced leakage current density, it leads to a higher turn-on voltage than standard LEDs due to the lack of p-doping, as well as an observed resistance to hole injection.

As such, the authors deduced that either through the development of p-type doping strategies, or advanced engineering schemes that remove polarization-induced barriers to electron recombination, AlScN can be optimized as an EBL. They expect their work to guide the utilization of AlScN in various photonic devices.

“The most compelling prospect is the realization of an AlScN-based quantum cascade laser,” said author Pierce Lonergan. “The lattice-matching conditions and large conduction band offset at the AlScN/GaN interface present an opportunity to explore these novel intersubband devices.”

Source: “AlScN as an electron blocking layer in blue light emitting diodes: A first look,” by Pierce Lonergan, Madhav Ramesh, Shivali Agrawal, Debaditya Bhattacharya, Thai-Son Nguyen, Vladimir Protasenko, Henryk Turski, Huili Grace Xing, and Debdeep Jena, Applied Physics Letters (2026). The article can be accessed at https://doi.org/10.1063/5.0310893 .

This paper is part of the Frontiers in Nitride Semiconductors Research Collection, learn more here .