Re-examination of effects of sulfur treatment on Al2O3/InGaAs metal-oxide-semiconductor interface properties

The effects of wet chemical treatments before treatment using (NH4)(2)S solutions in atomic layer deposition Al2O3/InGaAs metaloxide-semiconductor (MOS) interfaces are experimentally examined. It is found that no chemical treatment before sulfur passivation leads to high interface state density (D-it) in spite of the (NH4)(2)S treatment. Furthermore, the value of D-it is dependent among the pretreatments using NH4OH, HCl, and BHF solutions before the sulfur treatment. HCl + (NH4)(2)S and BHF + (NH4)(2)S combinations show the lowest values of D-it. In addition, all of the Al2O3/InGaAs MOS interfaces with the sulfur treatment show a small amount of arsenic oxide. Thus, much higher D-it of the interfaces with the sulfur treatment indicates that the amount of arsenic oxide is not a deterministic factor for D-it. On the other hand, the amount of arsenic oxide before the sulfur treatment is found to correlate with D-it after sulfur treatment. Also, the interfaces with higher D-it after the sulfur treatment show a larger number of sulfur atoms remaining at the interfaces. These experimental results mean that there is a strong correlation among D-it, the amount of arsenic oxide, and the number of sulfur atoms remaining at the Al2O3/InGaAs interfaces. As a result, we can interpret for the present experimental results that the sulfur treatment can have two opposite impacts on D-it at the Al2O3/InGaAs interfaces: the decrease in D-it due to etching of native oxides and suppression of oxidation by sulfur passivation and the increase in D-it due to defect generation through some interaction between sulfur and arsenic oxide. Published under license by AIP Publishing.