3C-Silicon Carbide (SiC) as a material of choice for high-performance low-cost power electronic devices

  • Anastasios Arvanitopoulos

    Student thesis: Doctoral ThesisDoctor of Philosophy


    The high power density requirements of modern power electronics applications has made
    Wide Band Gap (WBG) semiconductors to be considered as the next generation electronic
    material. The supreme electrical and thermal properties of the WBG compounds, such as
    Silicon Carbide (SiC) and Gallium Nitride (GaN), offer the potential for power devices with
    the capacity to outperform their Silicon (Si) counterparts. Yet, the shifting from Silicon
    to WBG technologies is not rapid, but rather occurs gradually. This is mainly due to the
    higher WBG process cost compared to the conventional Si devices, which still constitutes an
    established and reliable technology platform.
    The focus of this thesis is on the cubic phase of SiC, also referred to as β- or 3C-SiC,
    and power devices based on this compound. Owing to its cubic symmetry, 3C-SiC can be
    grown on top of large Si substrates (3C-SiC-on-Si) enabling cost-effective and isotropic
    WBG performance. These advantageous characteristics, coupled with recent advancements
    on the bulk 3C-SiC-on-Si material quality, highlight β-SiC as an emerging technology for
    power devices.
    The stepping stone towards investigating the true potential and the boundaries of this
    emerging SiC technology, comprises the development of an accurate material model for
    3C-SiC compatible with Technology Computer Aided Design (TCAD) software tools, which
    is reported in this thesis and did not exist prior. The material level validation of the 3C-SiC
    model with measurements enabled device level simulations and the derivation of an advanced
    defect-based model to justify the excessive leakage current evidenced in SiC Schottky Barrier
    Diodes (SBDs). The latter TCAD model, essentially links the presence of defects, both bulk
    and Schottky interface states, with complex trapping/de-trapping phenomena. In addition,
    the model accommodates for the inhomogeneous electrical behaviour of the Schottky Barrier
    Height (SBH). Overlapping spatial distributions of modelled trap profiles, featuring different
    energetic distributions, results in a non-uniform spatial distribution of the electric field on the
    Schottky active area.
    Thereafter, a simulation study compares the 3C-SiC with the more mature and commercialized 4H-SiC, in the context of power diodes, both Junction Barrier Schottky (JBS) and P-i-N. Static performance maps, in terms of on-state voltage drop and blocking voltage
    capabilities, are created and the limits of each technology are identified.
    The Carbon Cluster model allowed for the characterization of the various types of defects
    at the semiconductor / SiO2 interface. The 3C-SiC benefits from a relatively smaller band
    gap value to exclude the effect of specific traps, which majorly degrade the carriers’ mobility
    within the channel region of Metal Oxide Semiconductor (MOS) structures in other SiC
    polytypes. An additional model to accurately predict the high channel mobility of electrons
    demonstrated in 3C-SiC MOS-Field Effect Transistors (FETs) is presented and validated
    with measurements in this thesis, adding to the bulk mobility model.
    Nonetheless, 3C-SiC-on-Si MOSFETs are currently implausible following the conventional process for SiC unipolar power switches, due to the limited activation of the
    acceptor-type dopants with ion-implantation. A novel process for SuperJunction (SJ) JFET
    MOSFETs is proposed, considering two design splits, both evaluated with simulations. The
    results indicate that the suggested SJ JFET designs have the potential to deliver viable 3CSiC-on-Si MOSFETs with remarkable electrical performance, disrupting the current material
    Comprehensively, this thesis targets to model and analyze the effects of the traps existing
    in 3C-SiC-on-Si and, thereafter, investigate the true potential of high performance power
    diodes and MOSFETs based on the cubic phase of SiC grown on Si, given the recent
    improvements of the material quality
    Date of Award2021
    Original languageEnglish
    Awarding Institution
    • Coventry University
    SupervisorNeo Lophitis (Supervisor), Marina Antoniou (Supervisor), Konstantinos Gyftakis (Supervisor) & Mike Blundell (Supervisor)

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