The Differences in RF Semiconductor Materials and Their Advantages

September 1, 2021

Cadence System Analysis

Key Takeaways

RF semiconductors are used in the telecommunication, aerospace, automotive, and defense fields.
The range of circuits that employ RF semiconductor electronics is not limited to phase shifters, attenuators, couplers, filters, amplifiers, switches, oscillators, and antenna tuners.
RF semiconductor materials include gallium arsenide (GaAs), gallium nitride (GaN), silicon (Si), and silicon carbide (SiC).

Consumer electronics.

An increasing demand for consumer devices is one major factor supporting the growth of the RF semiconductor industry. RF semiconductors are used in the telecommunication, aerospace, automotive, and defense fields.

RF semiconductor materials include gallium arsenide (GaAs), gallium nitride (GaN), silicon (Si), and silicon carbide (SiC). These materials are significant in circuits such as RF filters, RF power amplifiers, RF low noise amplifiers, and RF switches. The differences in RF semiconductor materials cause variations in the speed and frequency characteristics of RF circuits, which is why it is critical for engineers to understand the differences in RF semiconductor materials.

The Increasing Popularity of RF Semiconductors

The RF semiconductor industry is fueled by LTE and advanced technologies such as 4G/5G. The considerable demand for wearable devices and smartphones have significantly boosted the turnover of RF semiconductor industries.

With the success of vehicle-to-vehicle and vehicle-to-infrastructure communication, new possibilities for RF semiconductors are being explored in the automotive field. Major players in the RF semiconductor markets have expanded their product portfolio after identifying the reach of RF devices in fields such as electronic warfare, radars, satellite communication, base stations, and transportation. Most of the big names in the RF semiconductor industry have invested billions in the research of new substrate materials, architectures, and packages by forecasting the monetary returns from present statistics.

The Differences in RF Semiconductor Materials

The range of circuits that employ RF semiconductor electronics is not limited to phase shifters, attenuators, couplers, filters, amplifiers, switches, oscillators, antenna tuners, etc. The frequency band is so wide that RF semiconductor devices cover VHF, UHF, SHF, and EHF frequencies. To integrate advanced features, extend the operating temperatures, frequency, and speed, or to increase the performance or efficiency, a myriad of RF semiconductor materials are introduced. Some of the RF semiconductors dominating the industry are given in the table below.

RF Semiconductor	Advantages
Silicon (Si)	Low cost Ease of fabrication High performance Integration of digital and analog circuits in a single-chip utilizing CMOS technology is possible
Germanium (Ge)	Main application is as a resistive material in RF MEMS and high mobility channel devices High resistivity value High refractive index and low optical dispersion
Silicon-Germanium (SiGe)	Wider gain bandwidth Lower noise performance Better power consumption and sensitivity
Gallium Nitride (GaN)	Wide bandgap material High breakdown voltage High power density High operating frequency High switching frequency High efficiency Excellent thermal conductivity
Gallium Arsenide (GaAs)	High electron mobility High thermal stability Low noise Wide temperature operating range
Silicon Carbide (SiC)	Large bandgap energy High electron mobility High critical breakdown electric field High thermal conductivity High power density High current density Operating temperature above 150℃ High switching frequency Low switching losses 6H SiC and 4H SiC are the polytypes of SiC available
Indium Phosphide (InP)	High breakdown voltage High thermal conductivity High electron saturation velocity High bandwidth Suitable for ultra-fast transistors
Boron Nitride (BN)	Graphene is integrated with BN to achieve high electron mobility High carrier velocity High-frequency operation Bo charge traps in BN substrate
Aluminium Nitride (AlN)	Excellent thermal conductivity Thermal expansion match to silicon Excellent resistance to wafer processing gases and plasma erosion Dielectric loss can be modified
Piezoelectric substrate	High RF power handling capacity Offers accurate resonant frequency for filter applications Low insertion losses and high out of band rejection Examples: LiNbO3, LiTaO3, ZnO

It is important to understand the differences in RF semiconductor materials to choose the appropriate material to fabricate RF devices. The careful selection of the semiconductor, architecture, and packaging has a direct influence on the performance of RF devices.

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