What is gallium arsenide?

Gallium arsenide (GaAs) is a compound built from the elements gallium and arsenic. It is often referred to as a III-V compound because gallium and arsenic are in the III group and V group of the periodic table, respectively.

The use of gallium arsenide is not a new technology. In fact, DARPA has been funding research into the technology since the 1970s. While silicon-based technology has been “the backbone substance of the microelectronics revolution, GaAs circuitry operates at the higher frequencies and signal amplification powers that have made practical a world connected by palm-sized cell phones.” 

Gallium arsenide led to the miniaturization of GPS receivers in the 1980s. This made the laser-guided, precision munitions that entered US arsenals during that time period possible.

Comparing GaAs, Si, SiC, and GaN bandgaps

With high electron mobility, semiconductor devices built of GaAs can function at frequencies in the hundreds of GHz.

While not truly considered a “wide bandgap” material, GaAs does have a considerably higher bandgap than silicon does. Critically, this makes GaAs highly resistant to radiation and therefore a great choice for defense and aerospace applications. Another selling point is that GaAs devices are far more resistant to heat and give off less EMI.

GaAs features a direct bandgap as opposed to silicon’s indirect bandgap. Because of this, GaAs can emit light much more effectively than can those made of silicon. This gives GaAs LEDs a clear advantage over those constructed of silicon.

A major advantage of silicon is that in the real world of mass manufacturing, silicon is far easier to work with. Silicon has a “native oxide,” silicon dioxide (SiO2). This ready insulator is an invaluable asset in fabricating silicon devices. GaAs has no analog.

Is gallium arsenide a better choice than silicon?

We’ve discussed some generalities and overall characteristics, but designers have to carefully analyze the particular needs of specific designs and not make their material choice based on preconceived notions. Sometimes, the answer won’t be what was initially expected.

In an article written by Analog Device’s Theresa Corrigan, N-channel CMOS MOSFETs are contrasted with GaAs devices when serving as wideband (900 MHz an higher) electronic switches.

The advantages of gallium arsenide

Low on resistance

Low off capacitance

High linearity at high frequencies

The advantages of CMOS

Loss of 3dB or less at 4 GHz 

Low power consumption 

No requirement for dc blocking capacitors 

High isolation between ports