Optical and electrical characterization of atomic layer deposited (ALD) HfO2/p-GaAs MOS capacitors

Abstract

The HfO₂/p-GaAs metal-oxide-semiconductor (MOS) structures have been fabricated by developing and simulating an optimized process recipe. The optical dielectric constants and refractive indices of atomic-layer-deposited (ALD) HfO₂ films and the GaAs substrate are extracted from spectroscopic ellipsometer (SE) measurements. The quality of interface and that of the ALD HfO₂ films is investigated by analyzing capacitance-voltage (C-V) and conductance-voltage (G-V) data. Simulations of C-V and G-V data have also been performed for a similar process recipe to comprehensively understand the electrical quality of the dielectric layer. The optical dielectric constants for HfO₂ and GaAs layers are obtained to be 4.5-3.6 and 10-25, respectively, while their refractive indices are obtained to be 2.12-1.89 and 3-5.2, respectively. A frequency dispersion of the C-V graphs is observed indicating the presence of a Ga₂O₃ interfacial layer which has been confirmed from the device simulation. A flat band voltage shift of − (0.68-1.05) eV and interface state density of (5×10¹¹ - 1 ×10¹²) cm^-2 eV^-1 are obtained.