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Abstract
Metal, typically gold [Au], nanoparticles [NPs] embedded in a capping metal contact layer onto silicon carbide [SiC] are considered to have practical applications in changing the barrier height of the original contacts. Here, we demonstrate the use of silver [Ag] NPs to effectively lower the barrier height of the electrical contacts to 4H-SiC. It has been shown that the barrier height of the fabricated SiC diode structures (Ni with embedded Ag-NPs) has significantly reduced by 0.11 eV and 0.18 eV with respect to the samples with Au-NPs and the reference samples, respectively. The experimental results have also been compared with both an analytic model based on Tung's theory and physics-based two-dimensional numerical simulations.
Highlights
Silicon carbide [SiC] has been proposed as the material of choice especially for power electronic and sensing devices operating under high temperature, fast switching, and high-power conditions mainly due to its wide bandgap (3.26 eV), high critical electric field (2.2 × 106 V/cm), superior thermal conductivity (4.9 W/Kcm), and high bulk electron mobility (900 cm2/Vs) of the 4H polytype [1,2]
We demonstrate that the work function change in the embedded metal NPs can effectively control the barrier height change of the SiC diode structures
Our results show that incorporating NPs with a larger work function difference to the capping metal layer results in an improved barrier lowering by further enhancing the local electric field
Summary
Silicon carbide [SiC] has been proposed as the material of choice especially for power electronic and sensing devices operating under high temperature, fast switching, and high-power conditions mainly due to its wide bandgap (3.26 eV), high critical electric field (2.2 × 106 V/cm), superior thermal conductivity (4.9 W/Kcm), and high bulk electron mobility (900 cm2/Vs) of the 4H polytype [1,2]. The effect of inhomogeneities and Fermi-level pinning on Schottky contact properties has been known to be minimal, and the barrier height depends mostly on the metal work function without strong Fermi-level pinning for SiC [4,5]. Recent work on the electrical contacts to SiC includes the implementation of nanostructures such as metal nanoparticles [NPs] to modify the barrier height at metal-SiC interfaces and to alter fundamental SiC device properties by controlling the size of the metal NPs. Previous results in the literature have been primarily focused on the effect of size reduction of NPs on the characteristics of diode structures with embedded NPs, which experimentally investigates the change in transport properties of metal/semiconductor interfaces in SiC depending on the size of NPs [5,6,7,8,9,10]. The experimental results have been compared with an analytic model based on Tung’s theory [11,12,13] and further verified by considering band diagram and electric field distribution using a physics-based two-dimensional numerical simulator Atlas (Silvaco Inc., Santa Clara, CA, USA) [19]
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