The effects of HCl treatment and predeposition vacuum annealing (VA) on n-type GaSb/GaAs metal–oxide–semiconductor (MOS) structures with the atomic layer deposition (ALD) of AlOdielectrics are studied. We obtained MOS structures with good Fermi level modulation by HCl treatment prior to the deposition of AlO. From X-ray photoelectron spectroscopy (XPS) analysis, we found that the GaO content increases during the AlO deposition, whereas the amounts of Sb components are reduced. The excess growth of GaO is inhibited by the reductions in the amounts of Sb components by the HCl treatment. Further reductions in the amounts of Sb components are observed following predeposition VA, indicating a lower density of states (D). However, the frequency dispersion in the capacitance–voltage (C–V) characteristics increases with predeposition VA at higher temperatures.
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