Diamond semiconductors exhibit exceptional performance in extreme environments, making them ideal for applications where conventional semiconductors fail. Their ultra-wide bandgap of 5.47 eV, high thermal conductivity exceeding 2000 W/m·K, and extreme mechanical hardness enable operation under high temperatures above 500°C, intense radiation, and corrosive conditions. These properties stem from diamond’s strong covalent bonding and low intrinsic defect density, but challenges remain in defect generation and dopant stability under extreme stress.

At high temperatures exceeding 500°C, diamond maintains electronic functionality where silicon and many compound semiconductors degrade. Silicon devices typically fail above 250°C due to intrinsic carrier generation and dopant diffusion, while gallium nitride (GaN) and silicon carbide (SiC) face limitations above 400°C. Diamond’s high Debye temperature of 2220 K ensures minimal phonon scattering, preserving carrier mobility. However, high-temperature operation accelerates defect formation, particularly vacancies and interstitials, due to increased atomic displacement. Boron-doped diamond, the most studied p-type variant, shows stable hole conduction up to 700°C, but excessive temperatures induce boron diffusion and compensation by intrinsic defects like nitrogen and vacancies.

Under radiation exposure, diamond demonstrates remarkable resilience. Its displacement threshold energy of 43 eV is higher than GaN (20 eV) and SiC (21 eV), reducing defect generation from particle bombardment. Neutron irradiation studies show diamond retains semiconducting properties up to fluences of 10^16 neutrons/cm², whereas GaN and SiC suffer significant lattice disorder at lower fluences. However, radiation-induced vacancies form complexes with dopants, degrading electrical properties. For instance, boron-vacancy centers in diamond act as deep traps, reducing carrier lifetime. Nitrogen-doped diamond exhibits better radiation tolerance due to nitrogen’s lower mobility and stronger bonding.

Corrosive environments, such as acidic or high-pressure aqueous conditions, challenge most semiconductors. Diamond’s chemical inertness allows operation in concentrated acids, bases, and saline solutions where GaN and SiC undergo surface oxidation or etching. Hydrogen-terminated diamond surfaces show stability in pH extremes, but oxygen termination degrades under prolonged exposure to oxidizing agents. Doped layers face additional risks; boron-doped diamond anodes in electrochemical environments experience gradual oxidation at potentials above 2.5 V vs. SHE, limiting long-term stability.

Defect generation mechanisms in diamond under extreme conditions follow distinct pathways. High temperatures promote vacancy clustering, forming divacancies and extended defects that act as recombination centers. Radiation generates Frenkel pairs (vacancy-interstitial pairs), with interstitials migrating rapidly even at room temperature. Corrosive conditions introduce surface defects, particularly at grain boundaries in polycrystalline diamond, where preferential etching occurs. Doped layers exhibit varied stability; boron remains substitutional up to 1200°C, while phosphorus-doped n-type diamond suffers from phosphorus-vacancy complex formation above 600°C.

Applications in aerospace leverage diamond’s thermal and radiation resilience. High-temperature sensors for jet engines and re-entry vehicles utilize diamond-based thermistors and pressure transducers. Diamond radiation detectors monitor cosmic rays and solar particle events in satellites, outperforming silicon detectors that require heavy shielding. Nuclear applications include diamond neutron detectors in reactor cores, where their radiation hardness and fast response time are critical. Diamond electrodes in nuclear waste processing resist corrosion from radioactive electrolytes.

Deep-well logging tools employ diamond semiconductors for high-temperature and high-pressure sensing. Diamond-based piezoresistive sensors measure downhole pressures up to 30,000 psi and temperatures exceeding 500°C, where silicon sensors fail. The oil and gas industry also uses diamond electrodes for corrosive fluid analysis, benefiting from their electrochemical stability in brines and hydrocarbons.

Compared to other wide-bandgap materials under stress, diamond excels in thermal conductivity and radiation hardness but faces challenges in doping control. GaN operates at higher frequencies but suffers from thermal runaway above 400°C due to lower thermal conductivity (130 W/m·K). SiC offers mature fabrication but exhibits higher defect generation under neutron irradiation. Aluminum nitride (AlN) has a wider bandgap (6.2 eV) but inferior carrier mobility and doping efficiency. The following table summarizes key comparisons:

Material | Bandgap (eV) | Thermal Conductivity (W/m·K) | Max Operating Temp (°C) | Radiation Tolerance (neutrons/cm²)
Diamond | 5.47 | >2000 | >700 | 10^16
GaN | 3.4 | 130 | ~400 | 10^14
SiC | 3.3 | 490 | ~600 | 10^15
AlN | 6.2 | 285 | ~500 | 10^14

Diamond’s primary limitation is the lack of reliable n-type doping, restricting bipolar device development. Phosphorus and sulfur doping yield low carrier concentrations (<10^17 cm⁻³), and their stability above 600°C remains unproven. In contrast, GaN and SiC offer both n-type and p-type doping with higher carrier densities.

Future advancements require improving doped layer stability and reducing defect generation. Optimizing growth techniques like microwave plasma CVD for lower defect densities and exploring new dopant configurations could enhance performance. Diamond semiconductors will continue enabling technologies in extreme environments where other materials cannot operate, provided these challenges are addressed.