From computational models to improved light-emitting diodes and new devices

Research output: ThesisDoctoral ThesisCollection of Articles


The rapid evolution of III-Nitride light-emitting diodes (LEDs) has started a solid-state lighting revolution leading to dramatic improvements in the efficiency of lighting and enabling a significant reduction in global energy consumption. Despite the progress, the operation of commercial LEDs can still be notably increased if the remaining challenges related to LED efficiency and efficiency droop, i.e., the decrease in efficiency at high input powers in particular, are solved. This thesis studies the factors affecting the performance of LEDs by using theoretical models and numerical simulations based on semiconductor transport equations and by analyzing measurement data and experiments. The main goal of the thesis is to generate new insight for understanding the present challenges of LED performance and for developing new device concepts for next-generation LEDs. The work has resulted, e.g., in the experimental demonstration of a fundamentally new current injection method, new insight on the droop mechanisms and current transport losses in LEDs, and better understanding of the potential benefits of polarization doping in LEDs. Results of this thesis can be used to design LEDs with higher efficiency and decreased droop, to develop next-generation LEDs that better exploit the possibilities offered by large light-emitting surfaces and nanowire light emitters, and to reduce transport losses in LEDs to improve carrier spreading and reduce the operating voltage.
Translated title of the contributionLaskennallisista malleista paranneltuihin ledeihin sekä uusiin fotoniikkakomponentteihin
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
  • Tulkki, Jukka, Supervising Professor
  • Oksanen, Jani, Thesis Advisor
Print ISBNs978-952-60-5991-4
Electronic ISBNs978-952-60-5992-1
Publication statusPublished - 2014
MoE publication typeG5 Doctoral dissertation (article)


  • light-emitting diodes
  • efficiency droop
  • numerical simulation
  • device physics


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