Terminology » RF Components » HBT vs HEMT: Key Differences Explained

HBT vs HEMT: Key Differences Explained

transistor hbt hemt rf semiconductor

This article compares HBT (Heterojunction Bipolar Transistor) and HEMT (High Electron Mobility Transistor), highlighting the key differences between these two types of transistors.

HBT - Heterojunction Bipolar Transistor

HBT structure

  • Full Form: Heterojunction Bipolar Transistor
  • Construction: An HBT is a type of BJT (Bipolar Junction Transistor) that uses different semiconductor materials for the Base and Emitter regions. This creates a heterojunction. Figure 1 (above) illustrates the internal structure of an HBT.
  • Materials: HBTs are typically made using materials like InP (Indium Phosphide) or InGaAs (Indium Gallium Arsenide).
  • Performance: HBTs are capable of handling high-frequency signals, often in the range of several 100 GHz.
  • Applications:
    • Fast switching RF circuits
    • High power efficient devices, such as Power Amplifiers (PAs) used in mobile phones.
    • Monolithic optical ICs (Integrated Circuits), such as PIN-based photo detectors.

HEMT - High Electron Mobility Transistor

HEMT structure

  • Full Form: High Electron Mobility Transistor

  • Construction: Figure 2 (above) shows the internal structure of a HEMT. It is a type of FET (Field-Effect Transistor) that incorporates a junction between materials with different band gaps (i.e., a heterojunction). Instead of using doped regions like in MOSFET designs, HEMTs use band gaps as channels.

  • Materials: HEMTs often utilize materials such as GaAs (Gallium Arsenide), AlGaAs (Aluminum Gallium Arsenide), and InGaAs.

  • Applications:

    • HEMTs are typically used at very high frequencies, such as millimeter-wave bands.
    • ON-OFF digital switches
    • Low power amplifiers
    • Satellite receivers

  • Advantages:

    • Higher Gain
    • Higher Switching Speed
    • Low Noise