Effects of Nitrogen Incorporation in HfO2 Grown on InP by Atomic Layer Deposition: An Evolution in Structural, Chemical, and Electrical Characteristics
2014
Kang, Yu-Seon | Kim, Dae-Kyoung | Kang, Hang-Kyu | Jeong, Kwang-Sik | Cho, Mann-Ho | Ko, Dae-Hong | Kim, Hyoungsub | Seo, Jung-Hye | Kim, Dong-Chan
We investigated the effects of postnitridation on the structural characteristics and interfacial reactions of HfO₂ thin films grown on InP by atomic layer deposition (ALD) as a function of film thickness. By postdeposition annealing under NH₃ vapor (PDN) at 600 °C, an InN layer formed at the HfO₂/InP interface, and ionized NHₓ was incorporated in the HfO₂ film. We demonstrate that structural changes resulting from nitridation of HfO₂/InP depend on the film thickness (i.e., a single-crystal interfacial layer of h-InN formed at thin (2 nm) HfO₂/InP interfaces, whereas an amorphous InN layer formed at thick (>6 nm) HfO₂/InP interfaces). Consequently, the tetragonal structure of HfO₂ transformed into a mixture structure of tetragonal and monoclinic because the interfacial InN layer relieved interfacial strain between HfO₂ and InP. During postdeposition annealing (PDA) in HfO₂/InP at 600 °C, large numbers of oxidation states were generated as a result of interfacial reactions between interdiffused oxygen impurities and out-diffused InP substrate elements. However, in the case of the PDN of HfO₂/InP structures at 600 °C, nitrogen incorporation in the HfO₂ film effectively blocked the out-diffusion of atomic In and P, thus suppressing the formation of oxidation states. Accordingly, the number of interfacial defect states (Dᵢₜ) within the band gap of InP was significantly reduced, which was also supported by DFT calculations. Interfacial InN in HfO₂/InP increased the electron-barrier height to ∼0.6 eV, which led to low-leakage-current density in the gate voltage region over 2 V.
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