Silicon carbide (SiC) is a wide-bandgap semiconductor with exceptional properties that make it highly suitable for optoelectronic applications, particularly in ultraviolet (UV) photodetectors and light-emitting diodes (LEDs). Its wide bandgap, high thermal conductivity, and chemical stability enable operation in harsh environments where conventional semiconductors like silicon or gallium arsenide would fail. The material’s ability to function under high temperatures, high voltages, and intense radiation makes it indispensable for advanced optoelectronic systems.

The bandgap of SiC varies depending on its polytype, with 3C-SiC having a bandgap of approximately 2.3 eV, while 4H-SiC and 6H-SiC exhibit bandgaps of about 3.2 eV and 3.0 eV, respectively. These wide bandgaps allow SiC-based devices to operate efficiently in the UV spectrum, particularly in the UVA (320–400 nm) and UVB (280–320 nm) ranges. Unlike silicon, which absorbs poorly in the UV region, SiC demonstrates strong UV absorption, making it ideal for photodetection applications. However, the wide bandgap also presents challenges for light emission, as achieving efficient radiative recombination requires precise doping and defect engineering.

Doping SiC for optoelectronic applications is complex due to the high activation energies of common dopants. Nitrogen is frequently used as an n-type dopant, while aluminum serves as a p-type dopant. However, achieving high p-type conductivity is particularly difficult because of aluminum’s deep acceptor level, which results in low hole concentrations at room temperature. This limitation affects the performance of SiC-based LEDs, as inefficient hole injection reduces internal quantum efficiency. To mitigate this, researchers have explored modulation doping and superlattice structures to enhance carrier mobility and injection efficiency.

One promising approach to improving optoelectronic performance involves the use of heterostructures, such as SiC/AlGaN systems. AlGaN, another wide-bandgap material, can be lattice-matched or nearly lattice-matched to SiC, reducing interfacial defects that degrade device performance. Such heterostructures enhance carrier confinement and improve light extraction efficiency in LEDs. Additionally, the combination of SiC with AlGaN enables tunable emission wavelengths in the UV spectrum, which is valuable for applications like UV sterilization, environmental monitoring, and secure communications.

Quantum efficiency is a critical metric for optoelectronic devices, encompassing both internal quantum efficiency (IQE) and external quantum efficiency (EQE). In SiC-based UV photodetectors, IQE is typically high due to the material’s strong UV absorption and low defect density when properly synthesized. However, EQE can be limited by surface recombination and poor light extraction. Anti-reflective coatings and surface passivation techniques are often employed to minimize these losses. For LEDs, the challenge lies in enhancing radiative recombination over non-radiative pathways. Techniques such as polarization engineering in SiC/AlGaN heterostructures have shown promise in improving IQE by aligning carrier recombination zones with regions of high radiative efficiency.

SiC-based UV photodetectors are widely used in flame detection, missile guidance, and solar UV monitoring due to their high sensitivity and fast response times. The material’s radiation hardness also makes it suitable for space-based UV sensors. In contrast, SiC LEDs face more significant hurdles in achieving high brightness and efficiency compared to III-nitride LEDs. Nevertheless, their robustness in extreme conditions makes them attractive for niche applications where reliability is paramount.

Recent advancements in defect engineering and epitaxial growth techniques have further enhanced the optoelectronic capabilities of SiC. For instance, the use of molecular beam epitaxy (MBE) and chemical vapor deposition (CVD) has enabled the growth of high-quality SiC films with reduced dislocation densities. Additionally, the development of nanostructured SiC, such as nanowires and quantum dots, has opened new avenues for improving light-matter interactions and quantum efficiency.

Despite these advancements, challenges remain in scaling SiC optoelectronic devices for commercial viability. The high cost of high-quality SiC substrates and the difficulty in achieving uniform doping across large areas are significant barriers. However, ongoing research into alternative growth techniques and defect passivation methods continues to push the boundaries of what is possible with SiC in optoelectronics.

In summary, silicon carbide’s unique properties position it as a leading material for UV photodetectors and specialized LEDs. Its wide bandgap, thermal stability, and compatibility with heterostructures like AlGaN enable high-performance optoelectronic devices capable of operating in demanding environments. While doping challenges and quantum efficiency limitations persist, innovations in material synthesis and device design are steadily overcoming these obstacles, paving the way for broader adoption of SiC in advanced optoelectronic systems.