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  1  Motivation

  1.2  Why HEMT?

HEMT is also known as heterojunction Field Effect Transistor (HFET), modulation-doped Field Effect Transistor (MODFET) or Two Dimensional Electron Gas Field Effect Transistor (TEGFET).

Transistors are used in many electronic devices such as switches, amplifiers or oscillators. HEMT transistors are able to operate at higher frequencies (up to millimeter wave frequencies) than ordinary transistors. They are used in high-frequency products such as cell phones, satellite television receivers, voltage converters and radar equipment. Therefore the HEMTs are an important components for high speed and high frequency digital and microwave circuits especially for low noise applications. HEMTs tend to satisfy growing demands of high power, high speed and high efficiency communications (Fig. 1.4).

Fig. 1.4 Five different semiconductor technologies vie for RF power-amplifier sockets in various applications, depending on power and spectral requirements.⁽¹⁾

RF power amplifier is the final active stage that drives the transmitting antenna. Power amplifier designs currently deployed use any of five semiconductor technologies: silicon LDMOS transistors, silicon-carbide (SiC) MESFETs, gallium-arsenide (GaAs) HEMTs, GaAs HBTs, and gallium-nitride (GaN) HEMTs.⁽¹⁾

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