Download HIGH RESOLUTION X-RAY DIFFRACTION AND TOPOGRAPHY

HIGH RESOLUTION X-RAY DIFFRACTION AND TOPOGRAPHY ANALYSIS
OF DEFECTS IN GaAs WAFERS
Kaspar Roosalu, Jaan Aarik, Hugo Mändar
Institute of Physics, University of Tartu, Estonia
e-mail: [email protected]
Silicon (Si), begin still the leader in the list of materials for electronic industry, is approaching to its
physical limits when the properties like high voltage, blocking voltage, current capability, operation at
high temperatures and frequencies are considered for high power and switching devices. Therefore
gallium arsenide (GaAs) gained considerable attention in power and high-frequency applications over
past decades already. Since defects (dislocations, inclusions etc.) have adverse effect on performance
of semiconductor devices, it is important to characterize the quality of GaAs devices in various
manufacturing stages, to optimize surface treatment and thin film growing methods in this respect.
In this study we have employed X-ray diffraction topography (XRT) (figure 1) method to visualize the
quality of GaAs wafer surface layers polished by mechanical and chemical procedures. R-ray
reflection (XRR) and X-ray diffraction (XRD) rocking curve (RC) measurements are conducted to
characterize the surface roughness, crystal mosaicity and presence of a damaged surface layer of GaAs
substrates and epitaxial GaAs layers. We show that results from XRT analysis are in good agreement
with RC measurements, and these methods in combination enable to select the wafers with lowest
concentration of defects.
Fig. 1 XRT patterns of GaAs epitaxial layer (left) and of corresponding GaAs substrate (right).
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