Investigation into the effects of electron-beam irradiation on III-nitride based LED devices

Publication Type:
Thesis
Issue Date:
2015
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The effects of low-energy electron irradiation (LEEBI) on the emission from InGaN/GaN multi quantum wells (MQW) LED devices have been systematically investigated using temperature-, power- and depth-resolved cathodoluminescence (CL) studies. In this work a dedicated CL system was developed to facilitate CL spectral spatial imaging as well as CL spectral time-resolved imaging over a broad temperature range from 10K to 750 K. LEEBI of InGaN/GaN MQWs has been previously described in the literature reporting effects such as formation of a new blue-shifted emission band from the as-fabricated MQW emission as well as both enhancement and quenching of the MQW emission. However, no clear explanation of the LEEBI induced modification of on the optical emission of MQW LED structures have been given up to now. It has been established in this work that LEEBI of In0.35Ga0.65N/GaN LED structures with an as-fabricated optical emission at 2.62 eVat 300K can produce an enhancement of the electroluminescence by over 2x. It was determined that this improvement is stable up to temperatures of 150 °C. Longer LEEBI irradiation quenched the 2.62 eVpeak and produce a different emission peak at 2.82 eV. Depth-resolved CL revealed that this new emission peak originates from the same depth as the MQW structure. These studies also confirmed that the LEEBI modification mechanism involves the electro-migration of H released from Mg-H complexes in the p-type capping layer that first passivates non-radiative recombination centres in the MQW increasing its light output and subsequently reacts with In within the MQW decreasing the localisation energy.
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