ICPS 2014

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8:30-9:00
Invited: Marco Piccardo
Determination of the Origin of Efficiency Droop in GaN LEDs by Electron Emission Spectroscopy
Co-authors: Jacques Peretti, Lucio Martinelli, Justin Iveland, James Speck, Claude Weisbuch, Marco Piccardo

In hot-electron semiconductor devices, carrier transport extends over a wide range of conduction states which often includes multiple satellite valleys. Electrical measurements can hardly give access to the transport processes over such a wide range without resorting to models and simulations. An alternative experimental approach however exists which provides, in a number of cases, very direct and selective information on hot-electron transport mechanisms. This approach based on low-energy electron spectroscopy was initially developed for the study of negative electron affinity semiconductor photocathodes and spin-polarized electron sources. We will here discuss recent electron emission spectroscopy results obtained in GaN LEDs. We show that the measurement of the electron spectrum emitted from the device under electrical injection of carriers provides a direct observation of hot-electron transport processes in the device. In particular, at high injected current density, high-energy features appear in the electro-emission spectrum simultaneously with the drop in light emission efficiency known as the droop phenomenon. These measurements evidence multivalley transport processes, as confirmed by complementary photoemission experiments, and allow us identifying the microscopic mechanism responsible for the droop which represents a major hurdle for widespread adoption of solid-state lighting.

9:00-9:15
Oral: M. Nazari
Self-Heating in a Two-Dimensional Electron Gas at the Interface Between GaN & AlGaN Studied by Ultraviolet & Visible Micro-Raman Scattering
Co-authors: Bobby Hancock, Edwin Piner, Jordan Berg, Mark Holtz

9:15-9:30
Oral: Masahiko Taguchi
Quantum Adiabatic Pumping with Tunneling Phase in Quantum Dot System
Co-authors: Satoshi Nakajima, Toshihiro Kubo, Yasuhiro Tokura

9:30-9:45
Oral: Logan Hancock
Junction Temperature & Electroluminescence Measurements in High Brightness Ultraviolet Light-Emitting Diodes
Co-authors: Bobby Hancock, Edwin Piner, Jordan Berg, Mark Holtz

9:45-10:00
Oral: Alexander Andrianov
Terahertz Electroluminescence from SiC p-n-Junctions Induced by Current Injection
Co-authors: Jay Gupta, James Kolodzey, Vladimir Sankin, Alexey Zakhar'in, Yury Vasilyev

10:00-10:15
Oral: Reuben Puddy
Multiplexing Large Arrays of Tunable Quantum Dots
Co-authors: Luke Smith, Haider Al-Taie, David Ritchie, Ian Farrer, Geb Jones, Michael Kelly, Michael Pepper, Charles G. Smith

10:15-10:30
Oral: Giancarlo Cerulo
Current Saturation Dependence on Self-Assembled Quantum Dot Density in Optically-Driven Electron Turnstiles 
Co-authors: Valeria Liverini, Laurent Nevou, Peter Friedli, Mattias Beck, Hans Sigg, Fabian Gramm, Jérôme Faist