Gallium arsenide (GaAs) is the most important non-silicon semiconductor. GaAs has many electrical properties superior to those of silicon. However, GaAs suffers from a few drawbacks that ensure that silicon (Si) will maintain its dominance in the future.
Useful properties of gallium arsenide
Unfortunate properties of gallium arsenide
- No high-quality insulators (counterparts to silicon dioxide) grow on GaAs. The insulator/GaAs interfaces have high levels of defects called "traps" that make GaAs MOSFET's impossible. This is probably the main reason that GaAs will never supplant Si as the semiconductor-of-choice for integrated circuits. GaAs transistors are usually either MESFET's or HEMT's. These transistors have some advantages over MOSFET's but their disadvantages outweigh the advantages.
- GaAs is extremely brittle. For this reason, GaAs wafers are typically smaller than three inches in diameter, as opposed to silicon wafers, which commonly have diameters of eight or more inches. Since the area on a wafer is proportional to the square of its diameter, Si has a huge cost advantage over GaAs.
- The hole mobility in GaAs is 15-20 times smaller than the electron mobility, which makes CMOS-like circuits unattractive.
Some material constants of gallium arsenide
I used these two references:
- Digital Integrated Circuits by Jan Rabaey
- CRC Handbook of Electromagnetic Materials by Perambur Neelakanta