Nitrides Seminar - Daniel Myers, Graduate Student Researcher
10/4/2018 12PM ESB 1001
Understanding efficiency loss mechanisms and electron transport in InGaN/GaN LEDs by electron emission spectroscopy
Daniel J. Myers, 1 Wan Ying Ho 1 , Abdullah Alhassan 1 , Kristina Gelzinyte, 2 Justin Iveland 1 , Jacques Peretti, 3 Claude Weisbuch, 1,3 James S. Speck 1
1 Materials Department, University of California, Santa Barbara, United States of America
2 Institute of Photonics and Nanotechnology, Vilnius University, Lithuania
3 Laboratoire de Physique de la Matière Condensée, CNRS-Ecole Polytechnique, Université Paris-Saclay, France
The development of GaN based light-emitting diodes (LEDs) has had a few long-term obstacles, most widely known is the loss of efficiency at increasing current density. The physical mechanism responsible for this phenomenon, was disputed in the scientific community for many years. In 2014, the first direct measurement of Auger-generated hot carriers produced in an LED active region was completed, using electron emission spectroscopy. These electron spectroscopy measurements were the first to directly show that efficiency droop was related to a hot carrier producing process, Auger recombination. The electron emission spectroscopy (EES) technique used in this study is unique in that the measured electrons are not produced by an external photoexcitation process but instead by electrical injection of the device. Because the electron source is the forward biased LED itself, the energy distribution of the emitted electrons is influenced by the relevant transport and recombination mechanisms which are occurring within the LED. In this way, the EES experiment can expand our understanding the underlying physics responsible for efficiency losses in LEDs and inform the engineering of solutions to these long-standing issues.