Applications of GaAsFETs in RF and Microwave Engineering

Key Takeaways

  • The two segments of FETs - junction field effect transistors (JFETs) and metal oxide semiconductor field effect transistors (MOSFETs) - are invariably used as amplifiers, analog switches, phase shift oscillators, current limiters, and in digital circuits.

  • In RF and microwave applications, GaAsFETs are the default solid-state device in use. 

  • High electron velocity benefits microwave circuits, which is why GaAsFETs are widely used in such applications. 

Field Effect Transistor

 Higher electron velocity, decreased parasitic capacitance, and easy fabrication are some of the features of GaAsFETs

The short physical wavelength of microwaves offers several unique features for applications. The application of microwave engineering includes (but is not limited to) short-distance communication, long-distance communication, cooking, and industrial heating. To develop microwave circuits, various semiconductor components are used.

Gallium arsenide field effect transistors (GaAsFETs) were introduced in 1970, and since then, GaAsFET-based high-speed integrated circuits, amplifiers, oscillators, attenuators, modulators, and limiters have been used in the microwave industry. GaAsFETs offer the following advantages: higher electron velocity, decreased parasitic capacitance, and easy fabrication. In this article, we will explore GaAsFETs and their advantages further.                        

The Market Demand for Field Effect Transistors

The growth of electronics, information, and communication engineering has continued to boost the market demand for field effect transistors (FETs). The two segments of FETs, junction field effect transistors (JFETs) and metal oxide semiconductor field effect transistors (MOSFETs) are invariably used as amplifiers, analog switches, phase shift oscillators, current limiters, and in digital circuits. The grade of the FET varies with end-user applications such as consumer electronics, automotive systems, power generation, IT, or telecommunications.

FET technology is extensively employed in integrated circuits due to its compact sizing. There are several types of FETs available, and the need to control power and miniaturize drives continued advancements in FET technology. 

GaAsFETs

GaAsFETs are a special type of FET used in microwave radio frequency applications. They are commonly employed in amplifier circuits at very high and ultra-high frequency applications. There are exceptional features showcased by GaAsFETs, including the following advantages:

  1. Higher electron velocity aids in achieving smaller transit time and faster responses.

  2. Semi-insulating GaAs substrate helps decrease the parasitic capacitance.

  3. Simple fabrication process.

  4. Sensitive and generates less internal noise.  

  5. The channel conductivity of GaAsFETs showcases dependency on the voltage applied to the gate terminal.

  6. Best-suited for applications including high linearity and high-frequency power.

  7. Among non-silicon counterparts, GaAsFET has cost advantages.

GaAsFET Properties

Among semiconductor devices, GaAsFETs are the top-priority class, as they exhibit the inherent electronic properties required for microwave applications. Some of these properties are:

High Electron Velocity

Among semiconductor devices, GaAsFETs have high electron mobility and direct band gaps. Their high mobility results in lower access resistance and accelerates the channel electrons to their saturated velocity rapidly over a short distance. The high electron velocity benefits microwave circuits, which is why GaAsFETs are widely used in such applications. 

Spatial Control of Charge  

Hetero-junction devices can be developed from GaAs device technology; this is widely accepted in the microwave industry, as it enhances the performance of the system. Combining compatible materials such as AlGaAs or InGaAs to form hetero-junction devices is effective in bringing spatial control of charges in microwave semiconductor devices. The introduction of AlGaAS or InGaAs in conjunction with GaAs optimizes device performance and establishes a higher degree of electron confinement.

Reduced Parasitic Capacitance 

The RF and microwave signals carried by GaAsFETs experience low attenuation due to the high resistivity of substrates. GaAs is a material of high resistivity, which provides the attributes of a semi-insulating substrate and decreases the parasitic capacitance in the device.

Challenges 

Thermal design is a challenge when working with GaAsFETs. The designer needs to identify issues such as heat dissipation through the substrate due to the low thermal conductivity of GaAs material or the dispersive phenomenon in GaAsFETs. Despite these challenges, GaAsFETs support microwave engineering applications by offering many advantages.

Designing for the Future With GaAsFETs

New developments in GaAs technology focus on bringing cutting-edge innovations to the RF and microwave engineering sector. Cadence can assist you in developing models of GaAsFETs from various manufacturers to help you analyze system performance.

Leading electronics providers rely on Cadence products to optimize power, space, and energy needs for a wide variety of market applications. If you’re looking to learn more about our innovative solutions, talk to our team of experts or subscribe to our YouTube channel.

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