What Is Compound Semiconductor?

Compound semiconductor is a class of crystalline solid-state materials formed from two or more elements drawn from different groups of the periodic table, whose combined electronic and optical properties exceed what elemental semiconductors such as silicon can provide. The most commercially significant families are the III-V compounds, in which a Group III element such as gallium or indium is paired with a Group V element such as arsenic, phosphorus, or nitrogen, and the II-VI compounds, formed from elements such as zinc, cadmium, selenium, and telluride. These materials are valued for electron mobilities, direct bandgap behavior, and high-frequency performance that make them indispensable in photonic and radio-frequency electronics.

Compound semiconductors occupied a secondary industrial role through much of the twentieth century while silicon dominated digital integrated circuits. Their trajectory shifted with the rise of mobile communications, fiber-optic networking, and solid-state lighting, all of which require physical properties that silicon cannot provide efficiently. The IEEE Electron Devices Society Compound Semiconductor Devices and Circuits Committee coordinates research and standardization activities across this device family, reflecting the breadth of ongoing development.

Material Properties and Band Structure

The defining advantage of III-V compound semiconductors is the direct bandgap available in materials such as gallium arsenide (GaAs), indium phosphide (InP), and gallium nitride (GaN). A direct bandgap allows electrons to transition between energy bands while emitting or absorbing photons efficiently, which makes these materials suitable for light emitters and detectors where silicon, an indirect-bandgap material, performs poorly. GaAs has an electron mobility of approximately 8500 cm²/V·s at room temperature, nearly six times higher than silicon, which enables faster carrier transit times and higher operating frequencies in transistors.

Bandgap engineering through heterostructures and ternary or quaternary alloys such as indium gallium arsenide (InGaAs) and aluminum gallium arsenide (AlGaAs) extends design flexibility. Epitaxial growth techniques including molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD) allow atomic-scale control over layer composition and thickness, enabling the quantum-well and pseudomorphic-channel structures used in high-electron-mobility transistors (HEMTs). Wide-bandgap materials such as GaN and silicon carbide (SiC) are classified as third-generation compound semiconductors and support high-voltage, high-temperature operation that first- and second-generation materials cannot sustain. The Sumitomo Electric review of compound semiconductor device development traces this generational progression and the device architectures that followed.

RF and Microwave Devices

Compound semiconductor transistors are the primary active elements in RF front-ends for wireless communications, radar, and satellite systems. GaAs pseudomorphic HEMTs and GaAs heterojunction bipolar transistors (HBTs) dominated handset power amplifiers through the 3G and 4G eras because their gain-bandwidth product and linearity at 1 GHz to 6 GHz met the demands of CDMA and LTE air interfaces. InP HEMTs achieve cut-off frequencies above 600 GHz in research devices and support millimeter-wave and sub-terahertz circuits for 5G backhaul and imaging systems.

GaN HEMTs on silicon carbide substrates deliver output power densities of 10 W/mm or higher, enabling compact high-power amplifiers for base stations, radar transmitters, and electronic warfare systems. The transceiver front-end of a modern wireless base station typically integrates GaN power amplifiers, GaAs or SiC switches, and InGaAs or GaAs low-noise amplifiers, with each compound semiconductor chosen for the specific electrical role it fills most efficiently. The ScienceDirect overview of compound semiconductor devices surveys the device structures and fabrication approaches used across this space.

Applications

Compound semiconductor has applications in a wide range of fields, including:

• Wireless communications transceiver front-ends for handsets and base stations
• Fiber-optic transmitters and receivers using InP-based laser diodes and photodetectors
• Solid-state lighting and display backlighting via GaN-based LEDs
• Satellite communications and phased-array radar using GaN and GaAs power amplifiers
• Wireless identification systems and RFID front-ends operating at microwave frequencies