GaNHEMTs

GaN HEMT stands for gallium nitride high-electron-mobility transistor. It is a type of lateral field-effect transistor that uses an AlGaN/GaN heterostructure to form a high-mobility two-dimensional electron gas at the interface. This 2DEG enables high current density and the ability to withstand strong electric fields, offering high breakdown voltages, fast switching, and relatively low on-resistance at high voltages.

Most GaN HEMTs are grown on substrates such as silicon, silicon carbide, or sapphire, with GaN-on-Si being common for cost-sensitive applications. The typical structure places a thin AlGaN barrier on GaN; polarization charges at the interface create the 2DEG without intentional doping, which contributes to the device’s performance advantages.

Operation and variants: Many GaN HEMTs are depletion-mode devices, meaning they are normally-on. To achieve normally-off operation, designers employ several approaches, including p-type GaN gates, MIS gates with dielectric layers, fluorine-doped gates, or cascode configurations. These schemes aim to improve safety and ease of integration in power-conversion circuits.

Performance and advantages: GaN HEMTs offer high breakdown voltages ranging from hundreds of volts to over 1 kV, high electron mobility, low on-resistance at high voltages, and very fast switching. These properties translate into high efficiency and reduced cooling requirements for high-frequency, high-power applications such as switch-mode power supplies and RF power amplifiers.

Challenges and reliability: Gate reliability, trapping at interfaces, current collapse, and threshold voltage shifts remain concerns. Thermal management is critical due to high power density. Ongoing work focuses on robust gate dielectrics, surface passivation, and packaging to improve reliability and lifetime.

Applications: GaN HEMTs are used in power electronics for AC-DC and DC-DC converters, motor drives, and inverters, as well as in RF amplifiers for telecommunications, radar, and automotive applications.