芯片级石墨烯/IGZO冷源FET阵列支持低于60mVdec−1超陡亚阈值摆动

1成果简介

本文，韩国忠北大学Woojin Park、Yonghun Kim、Byungjin Cho等研究人员在《ADVANCED MATERALS》期刊发表名“Chip-Scale Graphene/IGZO Cold Source FET Array Enabling Sub-60 mV dec−1 Super-Steep Subthreshold Swing”的论文，研究首次实现了石墨烯/铟镓锌氧化物（IGZO）冷源场效应晶体管（CSFET）阵列低于60 mV dec−1的超陡峭亚阈值摆幅（SS）。狄拉克锥型石墨烯的线性态密度抑制了石墨烯/IGZO界面附近的玻尔兹曼热尾，导致电子密度随能量增加呈超指数衰减，从而实现极低的关断电流和SS值。特别是，通过引入具有低体因子（body factor）的HfO2高介电常数介质，有效调制了表面电位，进一步将SS降低了≈46.4 mV dec−1。此外，在IGZO CSFET 8×8阵列器件中实现了高度均匀的亚60 mV dec⁻¹自激振荡，其产率达≈89.1%，并创下23.66 mV dec⁻¹的自激振荡值纪录，超越先前报道的氧化物半导体晶体管。该IGZO CSFET器件有望推动高速、超低功耗电子电路取得重大突破。

2图文导读

图1、a) Fabrication process and device scheme of the single-layer graphene-based IGZO CSFET. b) OM image of the graphene/IGZO CSFET integrated with an Al2O3 gate dielectric, and magnified image of the graphene/gate overlap structure. c) Cross-sectional TEM image of the graphene/IGZO/HfO2/SiO2 vertical stack. d) Deconvoluted XPS spectrum of the C 1s core peak in the graphene/IGZO layers. e) Raman spectroscopy spectra of the as-transferred graphene.

图2、a) 3D schematic of the IGZO cold-source transistor. b) Comparison between the surface potentials of IGZO and the graphene/IGZO surface. c) Output curves of IGZO CSFET with an Al2O3 gate dielectric under varying gate voltages from –1 to 1 V with a 0.5 V step. d) Drain current (left) at VDS = ± 1 V as a function of the applied gate voltage (VGS = –1 to 1 V), and rectification ratio (right) as a function of the same gate voltage range. e) Transfer characteristics of IGZO CSFET with an Al2O3 under the double-sweeping mode of VGS at a fixed drain voltage of VDS = 0.7 V (inset graph magnifies the hysteresis window). f) SS versus IDS density characteristics of IGZO CSFET with an Al2O3 at VDS = 0.7 V.

图3、a) Surface potential change of Pt/HfO2(or Al2O3)/p-Si capacitors with increasing voltage. b) Transfer characteristics of IGZO/HfO2 CSFET at VDS = 0.5 V (inset graph shows the lowest SS within a VGS of –1060 to –900 mV). c) Gate voltage-dependent µFE of IGZO CSFET with HfO2 at VDS = 0.5 and 0.7 V. d) SS value as a function of IDS density in the IGZO CSFET device with HfO2 at VDS = 0.5 V.

图4、a) Dynamic effective energy barrier (Φb.eff) change during on/off switching of the IGZO CSFET device with HfO2 (VDS = 0.7 V) (inset graph displays the temperature-dependent transfer characteristics). b) SS change as a function of drain current at various temperatures (293–403 K with a 10 K step) in the IGZO/HfO2 cold-source transistor. c) Temperature-dependent SS of IGZO CSFET with HfO2 at VDS = 0.7 V. Linear correlation between SS and temperature indicates a Schottky injection mechanism at the source/channel interface. d) Schematic of the E-k relationships, DOS, and electron densities of cold- and normal-source materials. e) Energy band diagrams of the IGZO/graphene CSFET in off-, mid-off, and on-state.

图5、a) Optical image of 8 × 8 IGZO CSFET array with HfO2. SS mapping images of b) graphene cold and c) Au/Cr hot-source transistor array based chips. White color indicates a failed device. d) Comparison of SS values versus VDS between this work and previously reported oxide-semiconductor transistors.

3小结

在本研究中，我们展示了石墨烯/IGZO冷源场效应晶体管阵列器件的超陡斜率开关特性。通过在源极引入狄拉克锥型半金属单层石墨烯，有效抑制了室温下源极费米能级以上的热尾效应，从而显著降低了单层石墨烯/IGZO界面处的电子浓度。通过采用SLG源极与Au/Cr背栅电极的局部重叠结构，实现了宽范围的势垒调制。KPFM分析证实了IGZO沟道与SLG冷源之间存在pn结。此外，与栅控效率相关的体因子成为有效调制表面电位的关键因素。最终采用体因子较小的介电常数高HfO₂材料，实现了低于60 mV dec⁻¹的开关特性。8×8石墨烯/IGZO/HfO₂冷源晶体管阵列展现出平均SS值达46.4 mV dec⁻¹的高性能，器件良率高达约89.1%。本石墨烯/IGZO冷源场效应晶体管有望为超低功耗电路及高性能电子应用的开发开辟新路径。

文献：https://doi.org/10.1002/adma.202510618

来源：材料分析与应用