In the particular case of III/V AlxGa1-xAs and InyGa1-yAs semiconductor structures electron energy loss spectroscopy (EELS) is more sensitive than energy dispersive X ray spectroscopy(EDS) This makes EELS useful for measuring compositional variations in these material systems with nanometer resolution in both linescan and imaging mode. An absolute precision of +/-0.02-0.03 and a relative precision of +/-0.01-0.02 in x can be reached at acquisition times of 1.5s/sspectrum. Using optimised acquisition and evaluation methods, concentration profiles and maps with a resolution in the nanometer range were obtained. When AlxGa1-xAs layers are grown by MOCVD on non planar GaAs substrates containing V-grooves and ridges, both self ordered Ga rich vertical layers (VQW) and Al rich vertical quantum barrier (VQB) regions were observed. For InyGa1-yAs layers deposited on such V-grooved structures, growth is furthermore influenced by strain. For the first time we could demonstrate that a vertical In rich region is formed in the centre of the groove with a local In excess concentration of Deltay=0.1 for a nominal y=0.15.
PEELS imaging and linescan study of concentration anisotropies in AlxGa1 xAs and in InyGa1-yAs heterostructures grown on non-planar substrates
G Biasiol;
1999
Abstract
In the particular case of III/V AlxGa1-xAs and InyGa1-yAs semiconductor structures electron energy loss spectroscopy (EELS) is more sensitive than energy dispersive X ray spectroscopy(EDS) This makes EELS useful for measuring compositional variations in these material systems with nanometer resolution in both linescan and imaging mode. An absolute precision of +/-0.02-0.03 and a relative precision of +/-0.01-0.02 in x can be reached at acquisition times of 1.5s/sspectrum. Using optimised acquisition and evaluation methods, concentration profiles and maps with a resolution in the nanometer range were obtained. When AlxGa1-xAs layers are grown by MOCVD on non planar GaAs substrates containing V-grooves and ridges, both self ordered Ga rich vertical layers (VQW) and Al rich vertical quantum barrier (VQB) regions were observed. For InyGa1-yAs layers deposited on such V-grooved structures, growth is furthermore influenced by strain. For the first time we could demonstrate that a vertical In rich region is formed in the centre of the groove with a local In excess concentration of Deltay=0.1 for a nominal y=0.15.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
