Key Parameters of Silicon Carbide (SiC) Substrates

Lattice Parameters: Ensuring that the lattice constant of the substrate matches that of the epitaxial layer to be grown is crucial to minimize defects and stress.

Stacking Sequence: The macroscopic structure of SiC consists of silicon and carbon atoms in a 1:1 ratio. However, different atomic layer arrangements result in various crystal structures. Therefore, SiC exhibits numerous polytypes, such as 3C-SiC, 4H-SiC, and 6H-SiC, corresponding to stacking sequences like ABC, ABCB, ABCACB, respectively.

Mohs Hardness: Determining the hardness of the substrate is essential as it affects the ease of processing and wear resistance.

Density: The density impacts the mechanical strength and thermal properties of the substrate.

Thermal Expansion Coefficient: This refers to the rate at which the substrate’s length or volume increases relative to its original dimensions when the temperature rises by one degree Celsius. The compatibility of the thermal expansion coefficients of the substrate and the epitaxial layer under temperature variations influences the thermal stability of the device.

Refraction Index: For optical applications, the refractive index is a critical parameter in the design of optoelectronic devices.

Dielectric Constant: This affects the capacitive properties of the device.

Thermal Conductivity: Crucial for high-power and high-temperature applications, thermal conductivity influences the cooling efficiency of the device.

Band-gap: The band-gap represents the energy difference between the top of the valence band and the bottom of the conduction band in semiconductor materials. This energy difference determines whether electrons can transition from the valence band to the conduction band. Wide band-gap materials require more energy to excite electron transitions.

Break-Down Electrical Field: This is the maximum voltage that a semiconductor material can withstand.

Saturation Drift Velocity: This refers to the maximum average velocity that charge carriers can attain in a semiconductor material when subjected to an electric field. When the electric field strength increases to a certain extent, the carrier velocity no longer increases with further increases in the field, reaching what is known as the saturation drift velocity.**

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