Low interfacial trap density and sub-nm equivalent oxide thickness in In0.53Ga0.47As (001) metal-oxide-semiconductor devices using molecular beam deposited HfO2/Al2O3 as gate dielectrics

Abstract

We investigated the passivation of In_0.53Ga_0.47As (001) surface by molecular beam epitaxy techniques. After growth of strained In_0.53Ga_0.47As on InP (001) substrate, HfO₂/Al₂O₃ high-κ oxide stacks have been deposited in-situ after surface reconstruction engineering. Excellent capacitance-voltage characteristics have been demonstrated along with low gate leakage currents. The interfacial density of states (D_it) of the Al₂O₃/In_0.53Ga_0.47As interface have been revealed by conductance measurement, indicating a downward D_it profile from the energy close to the valence band (medium 10¹² cm⁻²eV⁻¹) towards that close to the conduction band (10¹¹ cm⁻²eV⁻¹). The low D_it’s are in good agreement with the high Fermi-level movement efficiency of greater than 80%. Moreover, excellent scalability of the HfO₂ has been demonstrated as evidenced by the good dependence of capacitance oxide thickness on the HfO₂ thickness (dielectric constant of HfO₂ ∼20) and the remained low D_it’s due to the thin Al₂O₃ passivation layer. The sample with HfO₂ (3.4 nm)/Al₂O₃ (1.2 nm) as the gate dielectrics has exhibited an equivalent oxide thickness of ∼0.93 nm.