Martedì 16 aprile 2019
Ore 15.00
Sala Seminari, Piano I, Edificio U5 – via Roberto Cozzi 55, Milano
Relatore: Markus Pristovsek - Center for integrated Research of Future Electronics, Institute for Materials and Systems for Sustainability, Nagoya University, Japan
Titolo: What Limits the Efficiency of Green (0001) InGaN LEDs?
Abstract. The external quantum efficiency (EQE) of InGaN based LEDs reduces strongly from blue to the green spectral range. The main origin of this "green gap" is thought to be the reduced overlap of the electron and hole wave function due to the increased piezo-electric fields.
Our analysis of experimental EQE curves and carrier lifetimes suggests that non-radiative recombination is an important factor to the green gap. For semi-polar QWs the holes are badly confined, which allows for easy laser operation but bad LED performance, since the hole are likely to recombine at defects in the upper barrier.
Hence, the performance of green LEDs cannot be improved to match that of blue LEDs only by reducing the piezo-electric fields. Point defects and other sources of non-radiative recombination must also be addressed, either by applying appropriate semi-polar orientations or via Al containing interlayers.