Due to its outstanding material properties (most notably the high low-field
electron mobility of up to
)
gallium-arsenide has been the great hope of high-performance computing
for a long time. Unfortunately, not more than a hope, because of the
high manufacturing costs and the practical restriction to n-channel
devices, which in turn results in high power consumption (for similar
reasons as in the case of ECL).
Another reason why GaAs technology is not likely an option for future
VLSI technology is its poor speed scalability, which is due to the
electron saturation velocity
,
which is about the same as for
silicon.
This means that at small feature sizes silicon-based CMOS will catch
up with the speed of GaAs digital circuits at a fraction of the cost.
Regarding low-power electronics GaAs still offers advantages over silicon CMOS and even bipolar circuits. Despite the feasibility of high-frequency circuits in CMOS technology the achievable noise figure is much lower for GaAs, owing to its high low-field electron mobility. In comparison to silicon BJT circuits which can achieve a certain noise figure the same can be done in GaAs at much lower power. However, comparable improvements are being achieved with SiGe hetero-junction components such as HEMTs and HBTs (high electron mobility transistors and hetero-junction bipolar transistors).