Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 55: GaN: preparation and characterization II
HL 55.8: Vortrag
Freitag, 29. Februar 2008, 12:30–12:45, ER 164
Degradation of InGaN quantum wells during high temperature growth steps — •Holger Jönen, Daniel Fuhrmann, Daniel Dräger, Lars Hoffmann, Heiko Bremers, Uwe Rossow, and Andreas Hangleiter — Institute of Applied Physics, TU Braunschweig
The strong decrease of the internal quantum efficiency (IQE) of GaN based light emitters for longer wavelengths is well known. As possible reason for this behaviour the stronger piezoelectric field and a reduced material quality with increasing In content are often discussed. Furthermore, we found that with increasing In content the thermal stability of the layers becomes a critical issue. In this contribution we will focus on the thermal stability of InGaN QWs in LED structures grown by MOVPE. The quantum well growth is followed by a GaN spacer, AlGaN electron barrier and GaN capping layer. High temperatures are unavoidable during the MOVPE growth of these layers (e.g. for efficient Mg doping), in contrast to the low temperatures needed for high In concentration (xIn > 30%) in the quantum wells. Ramping the growth temperature is also commonly used for the barriers in MQW structures to improve the interface quality of the layers. The influence of such high temperature growth processes on the optical and structural properties of InGaN quantum wells is studied in detail. For this purpose we varied the growth parameters for the individual layers and found that the growth of the spacer layer is most critical and that the thermal budget of the GaN cap must be minimized.