Trap characterization of microwave GaN HEMTs based on frequency dispersion of the output-admittance

This paper presents a characterization method of traps in GaN HEMTs, based on the frequency dispersion of the output-admittance characterized by low-frequency S-parameter measurements. As RF performances of GaN HEMTs are significantly affected by trapping effects, trap characterization is essential for this power technology. The proposed measurement setup and extraction method allow us to derive the activation energy E_a and the capture cross section σ_n of the identified traps. A 0.25 μm gate length InAlN/GaN HEMT was characterized. A trap was identified with an activation energy of 0.38 eV, a capture cross-section of 1.73×10^-16 cm², and a field dependency of the emission rate. These results are used to give an efficient feedback to the technology developments.