Title : Theoretical analysis of structural, electrical, and optical considerations for AlGaN-based UVC-LED development
Abstract:
Nitrides are one important semiconductor family since the wide bandgap exhibited from the infrared to the ultraviolet spectrum. However, it is essential to mention that several issues lack an important improvement in the efficiency and optimization of material growth. Molecular Beam Epitaxy allows controlling the thickness and progress in the study of several applications of the nitride semiconductors for photodetector, solar cells, LASER, and light-emitting diodes. This work has studied the structural, optical, and electrical considerations to develop an LED structure allowing UVC-range applications. From the state-of-the-art study, the considerations for designing and simulating an AlGaN-based LED structure have been explored.
Additionally, from previously reported experimental Mg-acceptor limit in zb-GaN above 2.0x1019 cm-3 to set as the maximum p-type doping concentration for p-type AlGaN-layers and finite-element simulation of the entire LED structure. By DFT calculations, activation energy for p-type dopants and the maximum Al molar fraction under the direct-to-indirect cross point limit was determined according to the value of 0.75 reported in the current literature and DFT bands calculations. The activation energy reduction over 100 meV by substituting Be instead of Mg dopant by effective mass approximation modeling considering different p-type doping concentrations for zb-AlGaN. With these, a LED structure for wurtzite and zincblende approaches was performed by SILVACO simulation considering Vegard's law for the ternary values from zincblende binary parameters. From the state-of-the-art analysis, a thin low-Al-content layer has been added to reduce the impact of a high Al content in the AlGaN contact layer, improving the optical properties without a considerable lack of electrical performance.
What will the audience learn from your presentation?
• Zincblende and wurtzite LED structures were simulated where zb-AlGaN exhibits feasibility to develop UVC-LED.
• The direct-to-indirect bandgap cross point was determined around 0.75 Al molar fraction by DFT calculations, which corresponds to the state-of-the-art.
• DFT simulations exhibited around 100 meV reduction in the activation energy for p-type dopants comparing Be and Mg in a zincblende approach.
• The thin AlGaN layer and Be-doping in the p-type layer reduced Rs, improving the LED structure's electrical properties.
