Berlin 2012 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 25: Poster Session: GaN - Optical Properties & Preparation and Characterization & Devices
HL 25.26: Poster
Monday, March 26, 2012, 16:00–19:00, Poster D
Current-injection and carrier confinement in InAlGaN ultraviolet light emitting diodes — •M.-A. Rothe, T. Kolbe, J. Stellmach, F. Mehnke, T Wernicke, P. Vogt, and M. Kneissl — Institute of Solid State Physics, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
Ultraviolet (UV) light emitting diodes (LEDs) have attracted great interest in recent years because of their potential applications in phototherapy and sensing. However the external quantum efficiency (EQE) of these LEDs is only in low percentage range. One of the key challenges to improve the EQE is the carrier injection in to the active region. Therefore, an optimisation of the electron blocking layer (EBL) is very important to prevent an electron leakage into the p-layers of the LED with a simultaneous unhindered hole injection. In this work we have investigated 320 nm LEDs with different AlxGa1−xN:Mg EBLs. The devices were grown by metalorganic vapour phase epitaxy on (0001) sapphire substrates. A combination of electroluminescence measurements and simulations of the LED heterostructure were performed to investigate the carrier injection in the active region of the LEDs. We will compare LEDs with AlGaN EBLs with an aluminum content between 37 % and 48 % and show that the highest EQE is obtained for LEDs with an Al0.44Ga0.56N EBL. This is in a good agreement with our simulation results. The temperature effect on the performance of LEDs with different EBLs is investigated by temperature dependent electroluminescence measurements which shows a clear influence of the temperature on the electron leakage current of the UV LEDs.