ENERGY-DISPERSIVE X-RAY-IMAGING OF AN INGAN GAN BILAYER ON SAPPHIRE/

In this letter we discuss the potential and the limitations of quantit ative characterization of the distribution of In and Ga atoms in III-N mixed alloys using energy dispersive x-ray (EDX) analysis. Spatial fl uctuations of the indium content in an InGaN epilayer are found to cor respond to changes in luminescence efficiency. Large hexagonal pyramid s, which appear sparsely in such layers, appear to be relatively defic ient in indium. Monte Carlo simulations, used to profile the Ga K-a x- ray fluorescence, highlight several limitations of the EDX technique i n this context, but confirm our interpretation of the data. Finally, w e identify differential growth rates as a possible explanation for the concentration/efficiency variations in InGaN layers. (C) 1998 America n Institute of Physics. [S0003-6951(98)03448-2].