The Shrinking Wall
For decades, silicon transistors powered Moore's Law, relentlessly shrinking while boosting computing power. But as silicon devices approach atomic scales, electron slowdowns and energy leaks signal a fundamental ceiling. Enter indium gallium arsenide (InGaAs) – a compound semiconductor with electron mobility 10x higher than silicon. Integrating this high-speed material onto silicon platforms offers a lifeline to extend Moore's Law and unlock revolutionary efficiency for AI, quantum, and 5G/6G systems.
Electron Mobility Comparison
Key Advantages
-
10x Higher Mobility
Compared to silicon -
Lower Power Consumption
Reduced dynamic power -
CMOS Compatibility
New integration methods
Why InGaAs? The Electron Superhighway
Physics of Speed
InGaAs's crystal structure creates a "low effective mass" pathway for electrons, enabling near-ballistic transport. This translates to:
- Faster switching speeds at lower voltages
- Reduced dynamic power consumption
- Higher drive currents for computational density
| Property | InGaAs | Silicon | Advantage |
|---|---|---|---|
| Electron Mobility (cm²/Vs) | 10,000 | 1,400 | 7.1x |
| Saturation Velocity (×10ⷠcm/s) | 2.5 | 1.0 | 2.5x |
| Bandgap (eV) | 0.75 | 1.12 | Lower voltage |
The Crucible: MIT's Record-Breaking FinFET Experiment
MIT's 2025 VLSI Symposium presentation showcased a novel top-down fabrication process:
- Precision Etching
- Used reactive ion etching (RIE) with BCl₃/SiCl₄/Ar gas mix to carve 170nm-tall fins
- Applied 3 cycles of "digital etch" to trim widths to 8 nm 7
- Sidewall Perfection
- Treated fins with proprietary chemistry to reduce interface traps to 3×10¹² eVâ»Â¹cmâ»Â²
- Ohmic Contact Revolution
- Achieved contact resistivity of ~0.2 kΩ·µm – 50% lower than prior methods 7
SEM image of InGaAs fin structures (Source: MIT Research)
Results: A New Benchmark
| Metric | MIT Device | Prior InGaAs FinFETs | Si FinFET (Intel 14nm) |
|---|---|---|---|
| Fin Width | 8 nm | >15 nm | <10 nm |
| Aspect Ratio | 21:1 | <2:1 | >5:1 |
| Peak Transconductance | 1.8 mS/µm* | ~1.2 mS/µm | ~2.0 mS/µm |
| Normalized by Fin Width | 225 µS/nm | <80 µS/nm | 200 µS/nm |
*Per conducting gate periphery 7
First sub-10-nm InGaAs fins
With viable electrostatic control
55% higher transconductance
Than previous records
20nm gate lengths
Matching silicon roadmaps
The Scientist's Toolkit: Building Next-Gen Transistors
| Material/Reagent | Function | Innovation Impact |
|---|---|---|
| TMAH Solution | Selective InGaAs etching | Enables atomic-layer-precision fin shaping |
| Molybdenum Sputter Targets | Low-resistance ohmic contacts | Prevents Fermi-level pinning at interfaces |
| HfO₂/Al₂O₃ ALD Precursors | High-k gate dielectrics | Boosts gate control while minimizing leaks |
| In₀.₅₃Ga₀.₄₇As Epitaxial Wafers | Channel material growth | Lattice-matched to InP buffers on Si |
| Digital Etch Chemicals | Cyclic oxidation/etch agents | Achieves sub-10nm fin widths with smooth surfaces |
Beyond Logic: Photonics and Quantum Frontiers
Bandgap Tunability (0.35–1.42 eV)
Enables multi-functional chips for diverse applications
Photonics Integration
CMOS-integrated LiDAR and quantum dot lasers 5
The Road Ahead: Challenges and Horizons
- Mobility Collapse below 15nm fin widths requires band structure engineering
- p-Channel Deficiency – GaSb-based solutions are under exploration
- Thermal Management at >500W/cm² power densities
Conclusion: The Silicon-Compound Coevolution
The VLSI 2025 symposium reveals a pivotal shift: InGaAs is no longer a lab curiosity but a scalable CMOS technology. As MIT's finFETs demonstrate, atomic-scale precision + novel materials science can overcome historic barriers. With industry players like Aeluma and Imec advancing 300mm manufacturing, InGaAs-on-insulator may well power the zettaflop AI systems and fault-tolerant quantum computers of 2030 – ensuring silicon's legacy lives on through its compound successors.
"The transconductance gap between silicon and InGaAs finFETs is closing. What remains is an engineering optimization problem – not a physics limitation."