Identification of Auger effect as the dominant mechanism for efficiency droop of LEDs

Abstract

We discuss the unambiguous detection of Auger electrons by electron emission (EE) spectroscopy from a cesiated InGaN/GaN light-emitting diode (LED) under electrical injection. Electron emission spectra were measured as a function of the current injected in the device. The appearance of high-energy electron peaks simultaneously with the droop in LED efficiency shows that hot carriers are being generated in the active region (InGaN quantum wells) by an Auger process. A linear correlation was measured between the high energy emitted electron current and the “droop current” - the missing component of the injected current for light emission. We conclude that the droop originates from the onset of Auger processes. We compare such a direct identification of the droop mechanism with other identifications, most of them indirect and based on the many-parameter modeling of the dependence of the external quantum efficiency on the carrier injection.