IEEE Workshop on Wide Bandgap Power Devices and Applications in Asia (WiPDA Asia 2018)

352 / 2017-12-09 06:26:48

Carrier Transport mechanisms contributing to the sub-threshold current in 3C-SiC-on-Si Schottky Barrier Diodes

wide bandgap,Silicon Carbide Devices,subthreshold.,finite element model

Plenary track > Device characterization and modeling

In the context of wide band gap (WBG) semiconductors; it is well known that 3C- Silicon Carbide (SiC) on Silicon (Si) power devices can experience high subthreshold current, even with termination structures implemented. This can be mainly attributed to poor quality of epitaxially grown layers. The authors previously reported on the parameters and physical models of the bulk 3C-SiC aiming to credible Technology Computer Aided Design (TCAD) modeling and simulation but did not include the effect of non-idealities. This work focuses on investigating the sub-threshold current-voltage (I-V) characteristics of a 3C-SiC on Si Schottky Barrier Diode (SBD) which indirectly signifies the actual material quality. An advanced TCAD model is developed and the simulation results are compared to experimental measurements . The carrier transport mechanisms, how they are affected by possible energy levels and how they alter the subthreshold is investigated and reported. Due to lattice and thermal mismatch with the Si substrate the grown 3C-SiC layers become rich in deep levels. These in turn, introduce energy states in the forbidden bandgap region. In addition to the bulk deep levels, dangling bonds are formed due to the loss of semiconductor surface crystal periodicity. The resulting charge at the Schottky metal-semiconductor interface depends on the relative Fermi level (E_F ) position . This affects the image force lowering of the Schottky Barrier Height (SBH) and in turn strongly affects the sub-threshold current. Besides the inclusion of defects, modelling of the sub-threshold current in 3C-SiC SBDs also requires employing the temperature insensitive field emission or quantum barrier tunneling mechanism. The aforementioned mechanisms raise the probability of trap-assisted tunneling elevating the sub-threshold current. By including them in the model, excellent matching with the experimental measurements has been achieved and the effects of sub-threshold carrier transport mechanisms in 3C-SiC is investigated.