Interface Optimization of Passivated Er 2 O 3 /Al 2 O 3 /InP MOS Capacitors and Modulation of Leakage Current Conduction Mechanism

The effect of atomic-layer-deposition (ALD)-derived Al2O3 passivation layer on the interface quality of Er2O3/Al2O3/InP laminated stacks and the improvement of electrical performance has been investigated systematically. The chemical bonding states measured by high-resolution X-ray photoelectron spectroscopy (XPS) reveal that the ALD-derived Al2O3 passivation layer can effectively inhibit the diffusion of substrate elements to optimize the interface quality. Electrical characterizations show that the optimized sample has demonstrated improved electrical properties, including the large dielectric constant of 20 and the suppressed leakage current density of $4.10\times 10^{-7}$ cm2. In addition, the leakage current conduction mechanisms are also investigated as a function of thickness of Al2O3 passivation layer. The optimized interface state density extracted from the conductance method has reduced from $1.30 \times 10^{12}$ eV−1cm2 of Er2O3/InP to $7.27 \times 10^{11}$ eV−1cm2 of Er2O3/Al2O3/InP by adjusting the passivation layer thickness. As a result, it can be also confirmed that the passivation treatment is beneficial to inhibit the element’s diffusion and optimize the interface quality, significantly controlling the capacitor degradation caused by the leakage current through the stacked oxide layer.