GaN
Understanding GaN Technology
GaN has revolutionized RF power amplifier design. Its wide bandgap (3.4 eV vs 1.4 eV for GaAs) enables higher operating voltage, higher power density per unit gate width, and higher junction temperature. A single GaN transistor can replace multiple GaAs devices, reducing system size, weight, and complexity.
GaN Advantages
- Power density: 5-10 W/mm gate width vs 1-2 W/mm for GaAs. Enables compact, high-power amplifiers.
- High voltage: Operates at 28-50V drain voltage vs 5-12V for GaAs. Simplifies power supply design.
- Bandwidth: High impedance ratio enables wideband matching networks. Multi-octave power amplifiers are practical.
- Efficiency: Class F and continuous-mode GaN PAs achieve 60-80% drain efficiency.
- Ruggedness: Survives high VSWR mismatches without damage. Important for radar and EW applications.
GaN Substrates
- GaN on SiC: Best thermal performance. Standard for defense and high-power applications.
- GaN on Si: Lower cost, larger wafers. Growing rapidly for 5G and commercial applications.
Bandgap: 3.4 eV vs 1.4 eV
Breakdown field: 3.3 MV/cm vs 0.4 MV/cm
Power density: 5-10 W/mm vs 1-2 W/mm
Operating voltage: 28-50V vs 5-12V
Max junction temp: 225C vs 175C
Frequently Asked Questions
What is GaN used for in RF?
GaN is used for high-power RF transistors and amplifiers. It enables compact, efficient power amplifiers for radar, electronic warfare, 5G base stations, and satellite communications. GaN offers 5-10x the power density of traditional GaAs technology.
Is GaN better than GaAs?
For power amplifiers, GaN is superior in power density, efficiency, bandwidth, and ruggedness. For low-noise amplifiers, GaAs pHEMT still offers the best noise performance. The two technologies are complementary rather than competitive.
What is GaN on SiC?
GaN on SiC refers to GaN transistor layers grown on a silicon carbide substrate. SiC has very high thermal conductivity (3.5x better than silicon), which efficiently removes heat from the GaN device. This combination provides the best power handling and reliability.