Gallium arsenide (GaAs) is a compound semiconductor that delivers performance beyond the limits of silicon.

It particularly excels in three areas — speed, high-frequency performance, and optical response — making it a leading material in fields that demand top-tier performance, such as communications, optics, defense, and aerospace.

・Constituent elements: gallium (Ga) and arsenic (As)

・Crystal structure: zinc blende structure

・Band gap: 1.42 eV (direct-gap material)

・Electron mobility: approximately 8,500 cm²/V·s (more than three times that of silicon)

・Thermal conductivity: approximately 0.5 W/cm·K (about half that of silicon)

GaAs excels in optical, high-frequency, and high-speed response applications, though its relatively weak heat dissipation is a drawback.

1.Direct-gap semiconductor Able to efficiently emit and absorb light, making it ideal for LEDs and lasers.

2.High electron mobility Because electrons move quickly through it, it is well suited to high-speed communications and high-frequency amplifiers.

3.High electron saturation velocity Carrier velocity resists saturation even under high electric fields, enabling stable operation.

In short, GaAs is strong in both light and speed, while also offering excellent power efficiency.

GaAs is used across many high-performance devices.

・As an optical device material, it is used in LEDs and laser diodes (LDs), delivering high emission efficiency from the visible light range through the infrared.

・In communications, it is built into cellular base stations, satellite communication equipment, and radar systems, forming the core of high-frequency amplifiers and switching circuits.

・In supercomputers and space probes, it is used as a fast, low-noise logic circuit material.

・It also holds an important position in solar cells; GaAs cells, in particular, are widely used in space applications thanks to their resistance to radiation and high temperatures.

・As a photodetector material, it is used in photodiodes and LiDAR systems, offering excellent high-sensitivity infrared detection.

>1.HEMT (High Electron Mobility Transistor) Uses a heterojunction structure to maximize electron mobility. Used in high-frequency amplifiers and 5G communication equipment.

2.HBT (Heterojunction Bipolar Transistor) Achieves high gain and high speed through junctions between dissimilar materials. Widely used in millimeter-wave and satellite communication modules.

Because of this, GaAs is often called “the king of transistors for high-speed devices.”

・GaAs emits light efficiently across the visible-to-infrared range (850–900nm).

・It is widely adopted in LEDs, laser diodes, and optical communication devices.

・Layered structures combined with InGaAs and AlGaAs allow the emission wavelength to be precisely controlled.

GaAs is the leading representative of a “light-emitting semiconductor,” something silicon simply cannot achieve.

・GaAs multi-junction cells are the mainstream choice for space applications.

・They show little performance degradation even under high-energy radiation.

・Their conversion efficiency exceeds 30% — roughly 1.5 times that of silicon.

Despite the high cost, GaAs offers overwhelming reliability for space and defense applications.

・Manufacturing costs are high, as both gallium and arsenic are expensive.

・Arsenic (As) is toxic, requiring careful environmental and safety management.

・Producing large-diameter wafers is difficult, limiting production volume.

・Its low thermal conductivity makes heat-dissipation design critical for devices that generate significant heat.

While highly capable, GaAs is a material that must be applied selectively, in settings suited to its strengths.

・Optimizing performance through alloying with materials such as InGaAs and AlGaAs.

・GaAs-on-Si technology, which forms GaAs layers on silicon substrates to improve mass-production capability.

・Strengthening optoelectronic devices through quantum well structures and multilayer heterostructures.

・Next-generation integrated optical and electronic devices based on GaAs nanowires.

GaAs is evolving from a standalone material into a component of increasingly complex composite structures.

・GaAs is a compound semiconductor that excels in speed, high-frequency performance, and optical response.

・Because it is a direct-gap material, it is ideally suited to LEDs and optical communications.

・Cost, toxicity, and thermal management remain key challenges.

・Going forward, integration with silicon and adoption of 3D multilayer structures are expected to further expand its range of applications.

1.What is GaAs’s greatest advantage over silicon?

2.In which areas does GaAs fall short?

3.Name three major application fields for GaAs.

 

Column Supervisor: Koji Kakumoto (Otis Group Co., Ltd.)

After studying abroad and working in planning and development at a trading company, he joined Otis Group Co., Ltd. in 2011. While primarily working in the Corporate Planning Department, he has also served concurrently in manufacturing and technical divisions, and since 2018 has served as Representative Director, working to drive business growth and strengthen the organization.

 

This article is a general technical explanation intended for educational purposes and does not refer to any specific company, product, or technology.