A combined capacitance-voltage and hard x-ray photoelectron spectroscopy characterisation of metal/Al₂O₃/In_0.53Ga_0.47As capacitor structures

Capacitance-Voltage (C-V) characterization and hard x-ray photoelectron spectroscopy (HAXPES) measurements have been used to study metal/Al₂O₃/In_0.53Ga_0.47As capacitor structures with high (Ni) and low (Al) work function metals. The HAXPES measurements observe a band bending occurring prior to metal deposition, which is attributed to a combination of fixed oxide charges and interface states of donor-type. Following metal deposition, the Fermi level positions at the Al₂O₃/In_0.53Ga_0.47As interface move towards the expected direction as observed from HAXPES measurements. The In_0.53Ga_0.47As surface Fermi level positions determined from both the C-V analysis at zero gate bias and HAXPES measurements are in reasonable agreement. The results are consistent with the presence of electrically active interface states at the Al₂O₃/In_0.53Ga_0.47As interface and suggest an interface state density increasing towards the In_0.53Ga_0.47As valence band edge.