Edge emission from 265~nm UV-C LEDs grown by MBE on bulk AlN

TL;DR

This paper reports the development of UV-C LEDs emitting at 265 nm grown on bulk AlN substrates, demonstrating high current density, efficient edge emission, and detailed analysis of device performance and limitations.

Contribution

It introduces a novel edge-emitting UV-C LED structure grown by MBE on bulk AlN with high current density and efficient photon collection at 265 nm.

Findings

Achieved high current density up to 800 A/cm².

Demonstrated efficient edge emission with low differential on-resistance.

Identified n-contact resistance as a key series resistance contributor.

Abstract

UV-C LEDs pseudomorphically grown by MBE on bulk AlN substrates emitting at 265 nm are demonstrated. High current density up to 800 A/cm$^2$, 5 orders of on/off ratio, and low differential on-resistance of 2.6 m$\Omega\cdot$cm$^2$ at the highest current density is achieved. The LED heterostructure has a high refractive index waveguide core surrounded by n- and p-cladding layers similar to a laser diode designed for mode confinement at 270 nm to facilitate edge emission and collection of photons. Edge-emitting devices are made by cleaving the fabricated LEDs along the $m$-plane of the wurtzite crystal. Electrical injection results in emission of high energy 4.7 eV photons that are collected from the cleaved edge of the LEDs corresponding to the optical bandgap of the AlGaN active region. The contribution of power dissipation across the n- and p-regions of the diode is discussed. The n-contact resistance to n-AlGaN is identified as the largest contributor to the series resistance of the LED in the present generation of devices.