The pursuit of semiconductor materials capable of operating beyond the performance limits of conventional wide bandgap semiconductors like silicon carbide (SiC) and gallium nitride (GaN) has intensified in recent years. Emerging materials such as boron arsenide (BAs) and gallium oxide (Ga₂O₃) exhibit exceptional thermal, electronic, and optical properties that could redefine high-power, high-frequency, and high-temperature electronics. These nascent semiconductors promise to overcome intrinsic limitations in thermal conductivity, breakdown voltage, and efficiency, but significant material science challenges remain before they can be integrated into commercial applications.

Boron arsenide has garnered attention due to its ultrahigh thermal conductivity, theoretically predicted to exceed 1300 W/m·K at room temperature—surpassing even diamond. Experimental measurements have confirmed values around 1000 W/m·K in high-quality crystals, demonstrating its potential for thermal management in high-power electronics. Unlike diamond, which is electrically insulating, BAs is a semiconductor with a bandgap of approximately 1.5 eV, making it suitable for electronic applications where heat dissipation is critical. However, synthesizing defect-free BAs remains a challenge. Growth techniques such as chemical vapor transport (CVT) often introduce impurities and structural defects that degrade thermal and electronic performance. Achieving stoichiometric control and minimizing arsenic vacancies are key hurdles that must be addressed to realize its full potential.

Gallium oxide, particularly the beta-phase (β-Ga₂O₃), is another promising candidate with an ultra-wide bandgap of 4.8 eV, significantly higher than SiC (3.3 eV) and GaN (3.4 eV). This property enables a theoretical critical electric field strength of 8 MV/cm, allowing for thinner, more efficient power devices with lower conduction losses. Experimental devices have demonstrated breakdown voltages exceeding 2000 V, validating its potential for high-voltage applications. However, Ga₂O₃ suffers from poor thermal conductivity, typically below 30 W/m·K, which poses a major bottleneck for power-dense applications. Active research is exploring heterostructure designs and integration with high-thermal-conductivity materials like diamond or BAs to mitigate this limitation. Additionally, the lack of p-type doping in Ga₂O₃ restricts device design options, necessitating breakthroughs in defect engineering and dopant activation.

Another material of interest is aluminum nitride (AlN), with a bandgap of 6.2 eV and thermal conductivity around 285 W/m·K. While its thermal performance is inferior to BAs, its ultra-wide bandgap makes it ideal for deep-UV optoelectronics and high-power RF devices. Experimental AlN-based transistors have shown operation at temperatures above 500°C, but material quality issues such as dislocations and oxygen impurities degrade device reliability. Improving crystalline perfection through advanced epitaxial techniques like metal-organic chemical vapor deposition (MOCVD) is critical for enhancing performance.

Theoretical models predict that these materials could enable devices operating at junction temperatures beyond 300°C, far exceeding the 150–200°C limits of SiC and GaN. However, experimental results often fall short due to material imperfections. For example, while BAs theoretically offers unmatched thermal conductivity, real-world samples exhibit variability due to grain boundaries and point defects. Similarly, Ga₂O₃’s high breakdown field is compromised by trap states that increase leakage currents. Addressing these discrepancies requires advances in growth techniques, defect characterization, and passivation methods.

Key material science challenges include achieving scalable synthesis with controlled defect densities. For BAs, optimizing growth parameters to reduce arsenic loss and improve crystal uniformity is essential. For Ga₂O₃, developing reliable p-type doping or alternative unipolar device architectures could unlock new applications. Thermal management strategies, such as integrating heat-spreading substrates or engineered interfaces, must be refined to overcome intrinsic limitations. Furthermore, the long-term stability of these materials under high electric fields and thermal cycling needs thorough investigation to ensure reliability in harsh environments.

In conclusion, boron arsenide, gallium oxide, and aluminum nitride represent a new frontier in semiconductor materials, pushing beyond the boundaries of conventional wide bandgap technologies. While their theoretical properties are compelling, experimental realizations highlight the gap between prediction and practice. Overcoming synthesis challenges, defect control, and thermal limitations will determine their viability for next-generation electronics. Continued interdisciplinary research in crystal growth, doping, and device engineering is crucial to harness their full potential and enable transformative applications in power electronics, RF systems, and extreme-environment operation.