Enhanced semiconductor nanowires improve safety of deep ultraviolet light emitters

Deep ultraviolet light emitters have proven useful in sterilization, disinfection, water and air purification, and medical sensing. However, human exposure to longer wavelengths from these emitters presents major safety concerns. Aluminum gallium nitride, or AlGaN, possesses a tunable bandgap energy covering a wavelength range from 200 to 365 nanometers. Vafadar and Zhao investigate the potential of this semiconductor in deep ultraviolet light-emitting diode applications.

AlGaN nanowires are viable options for LEDs not only because of their wavelength range, but also because they are compact and can be mass produced. Compared to other compound semiconductors, Group III-nitrides have large spontaneous electrical polarization fields which can help electrical conduction.

However, the external quantum efficiency of AlGaN-based LEDs drops drastically as the light emission wavelength shortens.

“In AlGaN, the p-type hole conduction is problematic,” said Songrui Zhao. “The main idea of this work is improved hole conduction such that the device performance can be optimized.”

Polarization-enhanced tunnel junctions and a thin p-AlGaN layer were incorporated into the deep UV LED. The resulting emitter showed enhanced electrical and optical performance with a 250 nm-emitting nanowire and an external quantum efficiency of 0.01%.

“There are few short-wavelength devices using such an approach,” said Zhao. “This work represents the first report of an AlGaN nanowire deep ultraviolet light emitter with polarization-engineered tunnel junction and p-layer.

In future applications, these results may be applied to deep ultraviolet lasers for use in photonics and semiconductor devices.

Source: “AlGaN nanowire deep ultraviolet LEDs with polarization enhanced tunnel junction and p-AlGaN layer by molecular beam epitaxy,” by Mohammad Fazel Vafadar and Songrui Zhao, JVST: B (2022). The article can be accessed at https://doi.org/10.1116/6.0002037 .