Mitsubishi Electric has, for the first time in the world, elucidated the effects of frequency dispersion caused by crystal defects in a gallium nitride (GaN) transistor, a high-frequency transistor fabricated by depositing a GaN epitaxial layer on a GaN substrate, and demonstrated that frequency dispersion can be significantly suppressed.
This achievement makes it possible to consistently realize the inherently high performance of GaN,
contributing to the miniaturization, improved performance, and lower power consumption of high-frequency equipment, including industrial microwave heating systems that use GaN transistors.
In recent years, demand for high-power, high-efficiency GaN transistors has been rapidly increasing in high frequency fields, including industrial microwave heating systems used for chemical recycling, which converts waste plastics back into chemical raw materials, as well as 5G/6G base stations and radar systems.
Conventional GaN transistors have mainly been fabricated by forming a GaN epitaxial layer on a silicon
carbide (SiC) substrate because SiC has high thermal conductivity and provides effective heat dissipation.
However, crystal defects have been unavoidable during the film formation process due to the difference in materials between the substrate and the epitaxial layer.
These crystal defects impede the movement of electrons during high-frequency operation, causing frequency dispersion, in which current values vary depending on the frequency, and resulting in unstable device operation.
Consequently, complex correction using digital circuits had previously been required, making increased
overall system size and greater power losses significant challenges.
As part of a project commissioned by Japan’s Ministry of the Environment, Mitsubishi Electric has elucidated the effects of crystal defects on frequency dispersion through device characterization of GaN transistors incorporating GaN substrates, an area in which Japanese companies have particular strengths, using a new circuit analysis method that incorporates defect-related response.
By demonstrating, for the first time in the world, that frequency dispersion can be significantly suppressed on a GaN substrate and that flat frequency characteristics can be obtained, Mitsubishi Electric has made it possible to simplify the digital correction circuits that had previously been essential. This will contribute to the miniaturization, improved performance, and lower power consumption of high-frequency equipment.
