GaAs
Understanding GaAs Technology
GaAs has been the dominant semiconductor technology for RF and microwave electronics since the 1980s. Its higher electron mobility compared to silicon enables higher frequency operation and lower noise figure. The pHEMT (pseudomorphic HEMT) process is the workhorse for most commercial and military LNA and small-signal MMIC products.
GaAs Advantages
- Low noise: GaAs pHEMT achieves noise figures below 0.5 dB at L-band and below 2 dB at Ka-band.
- High frequency: GaAs ICs operate to 100+ GHz.
- Semi-insulating substrate: Enables high-Q passive components integrated on chip.
- Mature technology: Well-characterized, reliable, and widely available from multiple foundries.
GaAs Process Types
- pHEMT: Best noise performance. Standard for LNAs and low-noise mixers.
- mHEMT: Metamorphic HEMT with InGaAs channel. Better noise above 40 GHz.
- HBT: Heterojunction bipolar transistor. Used for power amplifiers and high-linearity circuits.
GaAs: 8,500 cm2/Vs
Silicon: 1,400 cm2/Vs
GaN: 1,500 cm2/Vs
InP: 5,400 cm2/Vs
GaAs pHEMT noise figure:
1 GHz: 0.3-0.5 dB
10 GHz: 0.5-1.0 dB
30 GHz: 1.5-2.5 dB
Frequently Asked Questions
What is GaAs used for?
GaAs is primarily used for low-noise amplifiers (LNAs), RF switches, mixers, and medium-power amplifiers in receivers, cellular handsets, satellite front ends, and test equipment. Its high electron mobility enables low noise and high-frequency operation.
Is GaAs better than silicon for RF?
GaAs is superior to silicon for noise figure, gain, and frequency of operation. However, silicon (SiGe BiCMOS) has become competitive up to ~30 GHz and offers lower cost and higher integration. GaAs remains preferred for applications requiring the best noise performance.
What is the difference between GaAs and GaN?
GaAs excels in low-noise, small-signal applications (LNAs, small-signal MMICs). GaN excels in high-power applications (PAs, radar transmitters). GaAs has better noise figure; GaN has higher power density. Most systems use both: GaAs LNA at the input, GaN PA at the output.