Point defect effects in AlGaN 270-nm light emitting diodes introduced by MeV electron and proton irradiation

Abstract

Point defects were controllably introduced into 270 nm AlGaN Light-Emitting Diodes (LEDs) by 5 MeV electron and 1.1 MeV proton irradiations to examine the effect on electrical and luminescent characteristics. The 5 MeV electron irradiations had only a marginal effect on the charge distribution, current flow, and electroluminescence of LEDs for electron fluences up to 4.5 × 1016 e/cm2 that cause very strong degradation in green, blue, and near-UV LEDs. This lack of changes is attributed to the much higher charge densities in quantum-wells (QWs) and quantum barriers (QBs) of the 270 nm LEDs and to higher bond strength in high Al mole fraction AlGaN layers. By contrast, irradiation with 1.1 MeV protons with a fluence of 1016 p/cm2 leads to more than two orders of magnitude decrease in charge density in the QWs and QBs, a strong increase in the series resistance, and the emergence of deep electron traps near Ec-0.5 eV. The difference is explained by a much higher density of primary defects produced by protons. The observed effects are compared to changes in performance caused by aging after high driving current.