Impact of Sulfur Passivation on Carrier Transport Properties of In_0.7Ga_0.3As Quantum-Well MOSFETs

• Main Authors: Jun-Gyu Kim, Hyeon-Bhin Jo, In-Geun Lee, Tae-Woo Kim, Dae-Hyun Kim
• Format: Article
• Language: English
• Published: IEEE 2021-01-01
• Series: IEEE Journal of the Electron Devices Society
• Subjects: In₀.₇Ga₀.₃As; MOSFET; passivation; carrier scattering mechanism; interface trap density; effective mobility
• Online Access: https://ieeexplore.ieee.org/document/9348904/

We investigated the impact of a sulfur passivation (S-passivation) process step on carrier transport properties of surface-channel In_0.7Ga_0.3As quantum-well (QW) Metal-Oxide-Semiconductor Field-Effect-Transistors (MOSFETs) with source/drain (S/D) regrowth contacts. To do so, we fabricated long-channel In_0.7Ga_0.3As QW MOSFETs with and without (NH₄)₂S treatment prior to a deposition of Al₂O₃/HfO₂ &#x003D; 1-nm/3-nm by atomic-layer-deposition (ALD). The devices with S-passivation exhibited a lower value of subthreshold-swing (S) &#x003D; 74 mV/decade and more positive shift in the threshold voltage (<inline-formula> <tex-math notation="LaTeX">$\text{V}_{\mathrm{ T}}$ </tex-math></inline-formula>) than those without S-passivation. From the perspective of carrier transport, S-passivated devices displayed excellent effective mobility (<inline-formula> <tex-math notation="LaTeX">$\mu _{eff}$ </tex-math></inline-formula>) in excess of 6,300 cm²/<inline-formula> <tex-math notation="LaTeX">$\text{V}\cdot \text{s}$ </tex-math></inline-formula> at 300 K. It turned out that the improvement of <inline-formula> <tex-math notation="LaTeX">$\mu _{eff}$ </tex-math></inline-formula> was attributed to reduced Coulombic and surface-roughness scatterings. Using a conductance method, a fairly small value of interface trap density <inline-formula> <tex-math notation="LaTeX">$({\mathrm{ D}}_{\mathrm{ it}}) = 1.56 \times 10^{12}$ </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">$^{-2}$ </tex-math></inline-formula>eV<inline-formula> <tex-math notation="LaTeX">$^{-1}$ </tex-math></inline-formula> was obtained for the devices with S-passivation, which was effective in mitigating the Coulombic scattering at the interface between the high-k dielectric layer and the In_0.7Ga_0.3As surface-channel layer.