11.3 Post Growth Characterization of Nitride Films - Auger Depth Profiling
Auger Depth Profiling is a combination of a standard Auger electron spectroscopy
system with a traditional argon ion sputtering system. A known amount of
the sample is sputtered away and an Auger spectra taken. By stopping the
sputtering process in intervals and taking Auger spectra determining the
peak to peak amplitude of selected elements a depth profile can be obtained
in terms of concentrations of the tracked elements versus sample depth.
Unfortunately this method is destructive, but accurate to within about
100 Å. The atomic concentrations obtained are usually less accurate
mainly due to preferential sputtering. An alternative method is Rutherford
Backscattering Spectroscopy which is non destructive, but usually less
accurate in terms of depth resolution.
Auger Depth Profiling was mainly used for determination of relative
film thicknesses (Ref. 47). For accurate film thickness determination the
sputtering rate has to be calibrated for GaN and AlN using a depth profiler.
Such a calibration sample is currently being analyzed. A sample film consisting
of several alternating layers of AlN and GaN on top of a GaN buffer layer
is shown in Figure 42 to demonstrate the technique.
Figure 42: Auger depth profile of a GaN/AlN Superstructure
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