Boron nitride (BN) is a wide-bandgap semiconductor with exceptional dielectric properties, making it a promising material for electronic applications. Its structural versatility, including hexagonal (hBN), cubic (cBN), and amorphous phases, allows for tailored dielectric performance. Among these, hBN stands out due to its layered structure, high thermal stability, and compatibility with 2D materials. The dielectric properties of BN are characterized by low leakage currents, high breakdown fields, and excellent thermal conductivity, which are critical for capacitors, gate dielectrics, and high-frequency devices.
In capacitor applications, hBN exhibits a dielectric constant (κ) in the range of 3–5, which is lower than traditional oxides like SiO₂ (κ ≈ 3.9) or high-κ materials such as HfO₂ (κ ≈ 20–25). However, its ultra-low dielectric loss (tan δ < 0.001) and high breakdown strength (>10 MV/cm) make it advantageous for high-energy-density capacitors. Unlike conventional dielectrics, hBN maintains stability at elevated temperatures, reducing performance degradation in power electronics. Additionally, its layered structure allows for integration into flexible capacitors, where traditional oxides suffer from cracking and delamination.
For gate dielectrics, hBN offers atomically smooth surfaces and minimal interfacial traps, which are critical for high-performance transistors. Its bandgap (~6 eV) and large band offsets with common semiconductors (e.g., graphene, MoS₂) suppress leakage currents more effectively than SiO₂ or Al₂O₃. In field-effect transistors (FETs) using 2D channels, hBN gate dielectrics have demonstrated subthreshold swings approaching the theoretical limit (60 mV/decade) and carrier mobilities exceeding those achieved with oxide dielectrics. The absence of dangling bonds on hBN surfaces reduces charge scattering, enhancing device performance.
High-frequency devices benefit from hBN's low dielectric loss and high thermal conductivity (~400 W/m·K in-plane). These properties minimize signal attenuation and Joule heating, which are critical for radio-frequency (RF) and millimeter-wave applications. Compared to SiO₂ or SiNₓ, hBN-integrated RF transistors exhibit improved power-added efficiency and cutoff frequencies. Its compatibility with other 2D materials also enables heterostructure-based devices, such as resonant tunneling diodes, with superior high-frequency response.
When compared to traditional oxides, BN’s primary advantage lies in its thermal and interfacial properties rather than its dielectric constant. High-κ oxides like HfO₂ or ZrO₂ provide stronger electrostatic control but suffer from higher leakage and reliability issues at nanoscale thicknesses. BN’s lower κ is offset by its ability to form defect-free interfaces, particularly in 2D material-based devices. Emerging 2D dielectrics, such as transition metal dichalcogenide (TMD) oxides, offer tunable κ values but lack BN’s thermal stability and mechanical robustness.
In summary, BN’s dielectric properties position it as a superior material for applications demanding low loss, high breakdown strength, and thermal resilience. While traditional oxides dominate in high-κ scenarios, BN excels in high-performance, miniaturized, and flexible electronics. Its integration into capacitors, gate dielectrics, and high-frequency devices highlights its potential to complement or replace conventional dielectrics in next-generation electronics.
The following table compares key dielectric properties of BN with traditional and emerging materials:
Material Dielectric Constant (κ) Breakdown Field (MV/cm) Dielectric Loss (tan δ) Thermal Conductivity (W/m·K)
hBN 3–5 >10 <0.001 ~400 (in-plane)
SiO₂ 3.9 10 0.01 ~1.4
HfO₂ 20–25 5–7 0.02 ~1.0
Al₂O₃ 9 7–9 0.01 ~30
MoO₃ (2D) 6–8 ~5 0.05 ~10
This comparison underscores BN’s balanced performance, particularly in environments where thermal management and low loss are critical. Future advancements in BN synthesis and integration techniques will further solidify its role in advanced electronic applications.