Where is GaN actually outperforming silicon today?
GaN is winning in applications that demand high switching speed and high efficiency, such as DC-DC converters, power supplies, and RF amplifiers. A fully integrated GaN half-bridge driver on a silicon substrate operated at over 1 MHz with 200 V input, achieving 90.7% efficiency in a buck converter [4]. This is far beyond what conventional silicon MOSFETs can do at that frequency without massive losses.
GaN also excels in reducing thermal resistance. A buffer-less GaN-on-silicon design cut the thermal resistance from the GaN layer to the substrate by an order of magnitude compared to conventional GaN-on-Si, reaching 11 ± 4 m²·K·GW⁻¹ — one of the lowest values ever reported on a non-native substrate [2]. That means the device runs cooler, lasts longer, and can handle more power.
Where does silicon still hold the edge?
Silicon remains the workhorse for low-voltage (under 100 V) and low-frequency (under 100 kHz) applications because it is cheaper, more mature, and has a vast manufacturing infrastructure. A 2022 comparison of 91 power MOSFETs showed that conventional silicon MOSFETs still offer the best cost-performance trade-off for many applications below 400 V and 100 kHz [3]. GaN's advantages only become decisive at higher voltages and frequencies.
Even in the high-power space, GaN is not universally replacing silicon — it is competing head-to-head with silicon carbide (SiC). For voltages above 1200 V, SiC currently has a more established track record and better thermal conductivity, though GaN is catching up with vertical device designs that achieve >1 kV breakdown with very low on-resistance [1][3].
What are the main challenges keeping GaN from taking over completely?
GaN faces several practical hurdles. Growing high-quality GaN on silicon substrates is difficult due to mismatches in crystal lattice and thermal expansion, which can cause cracking and defects. A 2023 review noted that 'melt-back etching' at high temperatures between GaN and silicon, as well as buffer trapping, can cause leakage and current collapse [6]. These issues require complex buffer layers that add cost and thermal resistance.
Another challenge is reliability under extreme conditions. While newer GaN-on-Si transistors (EPC7XXX series) showed excellent radiation resistance and electrical stability in 2022 tests [7], older generations suffered from dynamic on-resistance degradation. Additionally, GaN devices are still more expensive to manufacture than silicon for the same voltage rating, limiting their adoption in cost-sensitive markets like consumer electronics.
Sources used in this answer
(Invited) Vertical GaN Diodes: Effect of Growth Parameters, Indium Surfactants, and Device Development for High-Power Electronics
Vertical GaN p-n diodes achieved >1 kV breakdown voltage with a specific on-resistance of 0.28 mΩ·cm², among the best reported for vertical homoepitaxy GaN diodes.
Buffer‐Less Gallium Nitride High Electron Mobility Heterostructures on Silicon
Buffer-less GaN-on-Si design reduced thermal resistance to 11 ± 4 m²·K·GW⁻¹, an order of magnitude lower than conventional GaN-on-Si.
An Overview about Si, Superjunction, SiC and GaN Power MOSFET Technologies in Power Electronics Applications
Comparison of 91 power MOSFETs showed Si, SiC, and GaN each have optimal voltage, current, and frequency ranges; no single technology dominates all applications.
GaN-on-Si: Monolithically Integrated All-GaN Drivers for High-Voltage DC-DC Power Conversion
A fully integrated GaN half-bridge driver on Si operated at >1 MHz with 200 V input, achieving 90.7% efficiency in a buck converter.
Gallium Nitride Power Devices in Power Electronics Applications: State of Art and Perspectives
GaN HEMTs are most suitable for high-frequency, high-efficiency power converters, but face competition from SiC in high-voltage applications.
GaN-based power high-electron-mobility transistors on Si substrates: from materials to devices
GaN-on-Si power HEMTs face challenges from lattice/thermal mismatches and buffer trapping, but have made major breakthroughs in material growth and device fabrication.
Radiation Results for Modern GaN-on-Si Power Transistors
Latest GaN-on-Si power transistors (EPC7XXX) showed excellent radiation immunity and electrical stability under hard-switching, SEE, TID, and neutron tests.