Electrical analysis of 265 nm UV-C emitting AlGaN diode heterostructures grown by MBE on bulk AlN

Pseudomorphic growth of a UV-C laser diode heterostructure is demonstrated on a bulk AlN substrate by MBE. While stimulated emission is not observed under current injection, spontaneous emission at 265 nm is observed. Current densities up to 800 A/cm2, >5 orders on/off ratio at ±5 V, and a low differential on-resistance of 2.6 mΩ cm2 at the highest current density are achieved. The heterostructure has a high refractive index waveguide core surrounded by n- and p-cladding layers for mode confinement at 270 nm to facilitate edge emission and collection of photons. Edge-collection electroluminescence of the devices is achieved by cleaving the fabricated devices along the m-plane of the wurtzite crystal. Electrical injection results in the emission of high-energy 4.7 eV photons that are collected from the cleaved edge of the heterostructure, 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 these devices. Reduction of these resistances will allow these heterostructures to achieve lasing in the future.