Tailoring the oxygen concentration in Ge-Sb-O alloys to enable femtojoule-level phase-change memory operations

doi: 10.1088/2752-5724/aca07b

1.
Center for Alloy Innovation and Design (CAID), State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, People’s Republic of China
2.
School of Integrated Circuits, Huazhong University of Science and Technology, Wuhan 430074, People’s Republic of China

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Corresponding author: E-mail: wzhang0@mail.xjtu.edu.cn

摘要

Abstract: Chalcogenide phase-change materials (PCMs), in particular, the flagship Ge₂Sb₂Te₅ (GST), are leading candidates for advanced memory applications. Yet, GST in conventional devices suffer from high power consumption, because the RESET operation requires melting of the crystalline GST phase. Recently, we have developed a conductive-bridge scheme for low-power phase-change application utilizing a self-decomposed Ge-Sb-O (GSO) alloy. In this work, we present thorough structural and electrical characterizations of GSO thin films by tailoring the concentration of oxygen in the phase-separating GSO system. We elucidate a two-step process in the as-deposited amorphous film upon the introduction of oxygen: with increasing oxygen doping level, germanium oxides form first, followed by antimony oxides. To enable the conductive-bridge switching mode for femtojoule-level RESET energy, the oxygen content should be sufficiently low to keep the antimony-rich domains easily crystallized under external electrical stimulus. Our work serves as a useful example to exploit alloy decomposition that develops heterogeneous PCMs, minimizing the active switching volume for low-power electronics.
- phase-change memory /
- amorphous phase /
- low-power /
- conductive-bridge /
- decomposition
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Figure 1. Tailoring the degree of oxygen incorporation in Ge-Sb-O alloys. (a) The sketch of a potential conductive path inside the heterogeneous network consisting of Sb-rich crystalline nanodomains and Sb-poor glass matrix. (b) Schematic depicting the sputtering of a Ge₁₅Sb₈₅ alloy target with varied O₂ flux under a protective atmosphere (Argon), resulting in oxygen incorporation to various levels.

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Figure 2. Electrical and structural characterizations of GSO thin films. (a) The resistance-temperature (R-T) curves of Ge₁₅Sb₈₅ and four GSO thin films upon heating. (b) The room temperature XRD pattern measurements of the five annealed thin films obtained after R-T measurements done at 300 C. (c) The Raman spectra of the annealed thin films in the range of 100 and 250 cm^-1. The fitted E_g and A_1g modes are marked in green and blue, respectively. (d) The corresponding peak positions and FWHM values.

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Figure 3. High-resolution XPS spectra of (a) Ge 2p3/2 and (b) Sb 3d for as-deposited Ge₁₅Sb₈₅ thin films prepared under different oxygen flux. The blue and green regions represent the fitting of different components, and the sum of fitted curves are marked by red dash-dot line.

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Figure 4. Electrical performance of the GSO devices. (a) Schematic of the experimental setup for electrical testing of GSO devices in a probe station. (b) and (c) The current-voltage (I-V) characteristics of the GSO devices with heavy and light oxygen doping by DC sweeps. (d) The resistance-voltage (R-V) characteristics of the 2 sccm GSO device under RESET operation. The applied pulse waveform is shown in the inset.

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Figure 5. The sketch of different working modes as the oxygen concentration in GSO alloys increases. Upon SET operation, the ratio of crystalline/amorphous domains varies significantly as a function of oxygen concentration.

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