Electrical analysis of three-stage passivated In_0.53 Ga _0.47 As capacitors with varying HfO₂ thicknesses and incorporating an Al₂ O₃ interface control layer

The atomic layer deposition of high dielectric constant oxides like HfO₂ on III-V substrates such as In_0.53 Ga_0.47 As leads to a poor interface, with the growth of In_0.53 Ga _0.47 As native oxides regardless of the surface pretreatment and passivation method. The presence of the native oxides leads to poor gate leakage current characteristics due to the low band gap of the native oxides and the presence of potential wells at the interface. In addition, the poor quality of this interface leads to very large interface state defect densities, which are detrimental to metal-oxide-semiconductor-based device performance. A wide band gap interlayer replacing the native oxide layer would remove the potential wells and provide a larger barrier to conduction. It may also assist in the improvement of the interface quality, but the problem remains as to how this native oxide interlayer cannot only be removed but prevented from regrowing. In this regard, the authors present electrical results showing that the atomic layer deposition (ALD) growth of a thin (∼1 nm) Al₂ O₃ layer before the ALD growth of HfO₂ causes a removal/reduction of the native oxides on the surface by a self-cleaning process without subsequent regrowth of the native oxides. As a result, there are significant improvements in gate leakage current densities, and significant improvements in the frequency dispersion of capacitance versus gate voltage, even when a defective In _0.53 Ga_0.47 As epitaxial layer on an InP substrate is employed. Measurements at different temperatures confirm that the frequency dispersion is mainly due to interface state defect responses and another weakly temperature dependent mechanism such as border traps, after accounting for the effects of nonideal In_0.53 Ga_0.47 As epitaxial layer growth defects where applicable.