We have developed a new ultra-low field frequency-swept (FS) electrically detected magnetic resonance (EDMR) spectrometer to perform sensitive EDMR measurements of 4H-silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors at sub-millitesla (mT) magnetic fields. The new spectrometer design enables the detection of so-called ultra-strong coupling effects such as multiple-photon transitions and Bloch–Siegert shifts. In this paper, we present a new spectrometer design and discuss ultra-low field FS-EDMR sensitivity to both multiphoton transitions and Bloch–Siegert shifts of the FS-EDMR response. FS-EDMR effectively eliminates the interference of the sub-mT EDMR response from a near-zero field magnetoresistance (NZFMR) phenomenon that pervades the sub-mT regime in a magnetic field-swept EDMR scheme. We discuss an automatic power leveling scheme, which enables frequency sweeping. We also present results illustrating the Bloch–Siegert shift of the FS-EDMR response. Finally, we study the two-photon transition line shape in the 4H-SiC transistor as a function of the static field, in which we observe a collapse of the two-photon linewidth with decreasing static field and compare our results to the theory of two-photon absorption in EDMR.

中文翻译：

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超低场扫频电检测磁共振

我们已经开发了一种新型的超低频率扫频（FS）电检测磁共振（EDMR）光谱仪，用于对亚毫米级的4H碳化硅（SiC）金属-氧化物-半导体场效应晶体管进行灵敏的EDMR测量（ mT）磁场。新的光谱仪设计能够检测所谓的超强耦合效应，例如多光子跃迁和Bloch-Siegert频移。在本文中，我们提出了一种新的光谱仪设计，并讨论了超低场FS-EDMR对FS-EDMR响应的多光子跃迁和Bloch-Siegert位移的敏感性。FS-EDMR有效地消除了在磁场扫描EDMR方案中普遍存在的sub-mT体制中的近零磁场磁阻（NZFMR）现象对sub-mT EDMR响应造成的干扰。我们讨论了一种自动功率调平方案，该方案可实现频率扫描。我们还提出了说明FS-EDMR响应的Bloch-Siegert位移的结果。最后，我们研究了4H-SiC晶体管中双光子跃迁线的形状与静态场的关系，在该场中，我们观察到双光子线宽随着静态场的减小而崩溃，并将我们的结果与两个理论相比较。 EDMR中的光子吸收。