Indium nitride quantum dots could shine the light for next-generation fiber optics

The development of novel optoelectronic materials and devices is often limited by technical challenges in their fabrication processes. Indium nitride (InN), a promising material with potential application as infrared emitters in next-gen fiber optics due to its narrow band gap, is another example that currently faces these challenges.

Quantum dots are advantageous for deposition of heterostructures with large lattice mismatch, such as InN and GaN. Of great importance is the controlled growth on either the metal-polar or nitride-polar interface due to their opposite polarization fields. Reilly et. al. report the first evidence of wavelength-tuneable photoluminescence from N-polar InN quantum dots, grown using metal-organic chemical vapor deposition.

The researchers were able to grow InN N-polar quantum dots and thin layers on GaN-on-sapphire base layers, at temperatures between 580 and 640°C, with InN thicknesses from one to 20 nm. The resulting InN quantum dots demonstrated tuneable emission wavelengths from around 1.00 µm to beyond 1.55 µm at room temperature. The emission wavelengths were shown to be dependent on growth temperature, quantum dot size and InN layer thickness.

In contrast to previous publications, the photoluminescence of these InN quantum dots does not degrade upon capping with GaN.

“The ability to cap the InN quantum dots with thin GaN layers without change in photoluminescence intensity or wavelength is a key step towards incorporating multiple InN quantum dot layers into buried regions of device structures,” said author Caroline Reilly.

Source: “Infrared luminescence from N-polar InN quantum dots and thin films grown by metal organic chemical vapor deposition,” by Caroline E. Reilly, Cory Lund, Shuji Nakamura, Umesh K. Mishra, Steven P. DenBaars, and Stacia Keller, Applied Physics Letters (2019). The article can be accessed at https://doi.org/10.1063/1.5109734 .