Diamond is a unique semiconductor material with exceptional properties that make it highly suitable for high-power, high-frequency, and extreme-environment applications. Its ultra-wide bandgap of 5.47 eV, high breakdown field, and unmatched thermal conductivity set it apart from conventional semiconductors like silicon and gallium nitride. These characteristics enable diamond-based diodes and rectifiers to operate under conditions where other materials would fail, particularly in high-voltage, high-temperature, and radiation-intensive environments.

One of the most critical advantages of diamond is its high breakdown field, which exceeds 10 MV/cm. This property allows diamond-based devices to sustain much higher voltages before experiencing electrical breakdown compared to silicon (0.3 MV/cm) or GaN (3.3 MV/cm). The high breakdown field is a direct result of diamond’s strong covalent bonding and wide bandgap, which prevent avalanche breakdown at lower fields. This makes diamond an ideal candidate for high-voltage rectifiers and power electronics, where minimizing energy loss and maximizing efficiency are crucial.

Thermal conductivity is another area where diamond outperforms all other semiconductors. With a room-temperature thermal conductivity of around 2200 W/m·K, diamond dissipates heat far more effectively than silicon (150 W/m·K) or GaN (253 W/m·K). This property is particularly beneficial in power-dense applications, where heat buildup can degrade performance and reliability. Efficient thermal management reduces the need for complex cooling systems, enabling more compact and robust device designs.

Despite these advantages, fabricating diamond-based diodes presents several challenges, particularly in forming reliable Schottky and p-n junctions. Schottky diodes in diamond require high-quality metal contacts with well-defined barrier heights. However, achieving consistent Schottky contacts is difficult due to surface states, defects, and the tendency of diamond to form sp2 carbon at interfaces. Metals like gold, platinum, and molybdenum have been studied for Schottky contacts, but their barrier heights can vary significantly depending on surface preparation and termination. Hydrogen-terminated diamond surfaces exhibit unique surface conductivity, which complicates Schottky barrier formation but also opens opportunities for novel device configurations.

P-n junction formation in diamond is even more challenging due to the material’s extremely low intrinsic carrier concentration and difficulties in doping. Conventional diffusion doping is ineffective in diamond because of its tight crystal structure, so most doping is achieved through ion implantation or in-situ doping during growth. Boron is the most widely used p-type dopant, with activation energies around 0.37 eV, while n-type doping remains problematic. Phosphorus and nitrogen have been explored as n-type dopants, but their activation energies are high (over 0.5 eV), leading to poor room-temperature conductivity. As a result, most diamond diodes rely on unipolar or metal-semiconductor junction designs rather than traditional p-n junctions.

Radiation hardness is another area where diamond excels. Its strong atomic bonds and low atomic number make it highly resistant to displacement damage and ionization effects caused by radiation. Unlike silicon, which suffers from significant performance degradation under high radiation doses, diamond devices maintain functionality in environments such as space, nuclear reactors, and particle accelerators. This radiation tolerance, combined with diamond’s high-temperature stability, makes it suitable for sensors and electronics in harsh conditions where conventional semiconductors would fail.

High-temperature operation is a key advantage of diamond diodes. Most semiconductors experience increased leakage currents and reduced carrier mobility at elevated temperatures, but diamond’s wide bandgap minimizes intrinsic carrier generation, allowing stable performance up to 500°C or higher. This makes diamond-based rectifiers ideal for aerospace, automotive, and industrial applications where devices must endure extreme heat without active cooling. Additionally, diamond’s chemical inertness prevents oxidation and degradation at high temperatures, further enhancing reliability.

Diamond diodes have been demonstrated in various configurations, including Schottky barrier diodes (SBDs) and p-i-n structures. SBDs are particularly attractive for high-frequency applications due to their fast switching speeds and low forward voltage drop. However, achieving low on-resistance remains a challenge due to the difficulty in obtaining high carrier concentrations in diamond. Recent advances in defect engineering and surface treatments have improved contact resistance, but further optimization is needed to compete with silicon carbide and GaN devices in commercial applications.

Thermionic emission and tunneling mechanisms dominate current transport in diamond Schottky diodes, with ideality factors often exceeding unity due to interface states and inhomogeneous barriers. Temperature-dependent current-voltage analysis reveals the impact of defects and barrier height variations on device performance. Despite these challenges, diamond diodes have shown promising results in high-power rectification, with breakdown voltages exceeding several kilovolts and low reverse leakage currents.

In high-temperature and radiation-hardened applications, diamond diodes offer significant advantages over silicon and other wide-bandgap semiconductors. For example, diamond-based radiation detectors exhibit excellent energy resolution and stability under prolonged exposure to ionizing radiation. Similarly, high-temperature rectifiers maintain stable operation in environments where silicon devices would experience thermal runaway or catastrophic failure. These capabilities position diamond as a leading material for next-generation power electronics and extreme-environment electronics.

Future developments in diamond diode technology will likely focus on improving doping techniques, reducing defect densities, and optimizing device architectures. Advances in chemical vapor deposition (CVD) growth have already enabled higher-quality diamond films with lower impurity concentrations, but further progress is needed to achieve cost-effective production at scale. Hybrid approaches, such as combining diamond with other wide-bandgap materials, may also provide new opportunities for enhancing device performance.

In summary, diamond’s exceptional breakdown field, thermal conductivity, and radiation hardness make it an outstanding material for high-performance diodes operating in extreme conditions. While challenges remain in junction formation and doping, ongoing research continues to push the boundaries of what is possible with diamond-based devices. As fabrication techniques improve and new applications emerge, diamond diodes are poised to play a critical role in advancing power electronics, aerospace systems, and other high-stakes technologies.