Silicon Carbide (SiC) boasts superior electrical and mechanical properties, making it a go-to material for applications including high-power switches and aerospace electronics. Furthermore, its wide bandgap and thermal stability enable efficient performance at elevated temperatures and voltages.
SiC is widely renowned for its exceptional mechanical strength and hardness, resilience in harsh environments such as high-temperature sensors, radiation-hard electronics and radiation shielding applications, as well as its resistance to environmental corrosion.
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4H silicon carbide’s superior thermal conductivity of 1.89 milliWatt per K-1 makes it an ideal material for electronic and mechanical applications that operate at elevated temperatures and voltages, such as power or RF devices that need to operate at higher frequencies without increasing component sizes or risking overheating failure. Its thermal properties make 4H silicon carbide ideal for cutting-edge electronic and mechanical devices that operate under harsh environmental conditions, including temperatures exceeding 100Kdeg.
Thermal conductivity was measured on wafer-scale 3C-SiC bulk crystals using the TDTR technique with 5x objective and 9.3 MHz modulation frequency on samples that had been chilled to room temperature using an objective with 5x magnification and 9.3 MHz modulation frequency, using low frequency measurements in longitudinal direction that varied depending on strain tensile or compressive. At low frequencies with compressive strain applied phonon group velocity was constant while with increasing strain it decreased continuously with increasing strain levels.
To investigate the effect of impurity X on the thermal conductivity of 3C-SiC, we deliberately doped it with B in concentrations ranging from 1-2×1019 atoms cm-3 and measured its thermal conductivity. The results demonstrated that B impurities significantly reduced thermal conductivity as predicted by first principles calculations.
Figure 2a displays depth profiles of O, N and B atomic densities on a 3C-SiC growth face and Si substrate after secondary ion sputtering, in terms of O, N and B densities and doping concentrations characterized by doping energies (mSi, mC and mX) calculated using ShengBTE method with 36x36q-mesh mesh size and broadening factor of 0.149 for N and B doping concentrations respectively. Doping energies provide further detail as doping concentrations indicate doping concentrations as doping energies (mSi, mC and mX). Doping energies indicate concentrations for doping (N and B doped areas) doping concentrations are described by doping energies calculated from formation energies calculated using ShengBTE method calculations calculated from impurity formation energies calculated from formation energies using formation energy calculations on substrate using shengBTE method with 36 q-mesh array with broadening factor 0.149.
Electrical Conductivity
As well as boasting superior mechanical properties, 4H silicon carbide boasts excellent electrical and thermal conductivity properties that make it the go-to material for applications where high voltages and power densities are critical. Its superior electron mobility and saturation electron velocity enable efficient operation at elevated temperatures and voltages; making it suitable for electric vehicles (EVs), renewable energy systems, aerospace electronics as well as electric vehicle charging infrastructure. Lastly, its remarkable thermal conductivity facilitates superior heat dissipation ensuring device longevity.
4H SiC should be remembered to not be isotropic – meaning its material parameters differ along both its c-axis and perpendicular to it due to its hexagonal polytype structure, comprised of double layers.
Impurities play an essential role in shaping the electrical, optical and mechanical properties of 4H SiC. Depending on its site preference and atomic radius, impurities can either expand or contract the SiC crystal lattice, altering phonon dispersion patterns as well as electronic band structures.
Impurities play an essential role in the solubility of 4H SiC across various dielectrics. It is widely recognized that solubility depends on differences between impurity atomic radius and host silicon or carbon atom radius; higher differences lead to decreased solubility.
Piezoelectricity
Impurities play an essential role in shaping the electrical, optical, and mechanical properties of 4H-SiC materials. Impurities may occupy either Si or C lattice sites or interstitial positions depending on their preferred site and size; depending on their presence or absence in 4H-SiC materials this results in either lattice distortions or solubility issues that have an enormous impact on its structure and properties.
Utilizing a modified Kolsky bar technique, we studied the dynamic compressive deformation and damage behavior of two hexagonal polytypes (4H and 6H-SiC), along with their coupled electrical response, that exhibit similar damage evolution and threshold behavior for electrical response.
A comprehensive set of elastic constants was determined for the n-type epitaxial layer of 4H-SiC using a new method that utilizes weighted average of error calculations from density functional theory, yielding significant reduction in uncertainty.
An efficient heuristic method has been devised for determining the elastic constants of silicon carbide using an averaging principle similar to that employed for chemical molecular orbital calculations. This heuristic approach enables accurate elastic constant measurements across a broad spectrum of materials including silicon carbide; particularly beneficial in characterizing its n-type properties more accurately in recent times.
Optical Properties
4H-SiC’s wide bandgap allows for efficient nonlinear optical properties such as frequency conversion and nonclassical light state generation, making it suitable for lasers and other optical devices, particularly as a host material for solid-state atomic defect qubits used in quantum computing and communications.
4H-SiC also boasts strong magnetic properties, making it suitable for magnetoelectronics and data storage applications. Furthermore, its superior thermal conductivity and wide bandgap make it an excellent semiconductor choice for power electronics applications. 4H-SiC’s superior physical characteristics and nonlinear optical properties also make it a promising candidate for use in microelectronic components and MEMS devices.
To fully comprehend the complex behavior of SiC, it is crucial to take into account all dominant impurities in its system – this includes their atomic configurations, phonon properties and interactions with its crystal lattice. For instance, first principles calculations indicate that B-doping can lead to significant lattice distortion (see Fig 3); this phenomenon is believed to result from an empty e-state formed within its crystal which competes against vacuum bound states for resources and thus distorts its lattice structure.
Dopant-induced distortion of lattice structures is usually manifested as a shift in the fundamental transverse electric (TE) mode. To optimize this shift, temperature tuning must be implemented carefully to balance out defect energy levels and achieve optimal TE mode spectral shift.
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