The buffer and surface trapping effects on low-frequency (LF) Y-parameters of Fe-doped AlGaN/GaN high-electron mobility transistors (HEMTs) are analyzed through experimental and simulation studies. The drain current transient (DCT) characterization is also carried out to complement the trapping investigation. The Y22 and DCT measurements reveal the presence of an electron trap at 0.45–0.5 eV in the HEMT structure. On the other hand, two electron trap states at 0.2 eV and 0.45 eV are identified from the LF Y21 dispersion properties of the same device. The Y-parameter simulations are performed in Sentaurus TCAD in order to detect the spatial location of the traps. As an effective approach, physics-based TCAD models are calibrated by matching the simulated I-V with the measured DC data. The effect of surface donor energy level and trap density on the two-dimensional electron gas (2DEG) density is examined. The validated Y21 simulation results indicate the existence of both acceptor-like traps at EC –0.45 eV in the GaN buffer and surface donor states at EC –0.2 eV in the GaN/nitride interface. Thus, it is shown that LF Y21 characteristics could help in differentiating the defects present in the buffer and surface region, while the DCT and Y22 are mostly sensitive to the buffer traps.

The electron trapping in AlGaN/GaN high-electron mobility transistors (HEMTs) with iron (Fe)-doped buffer is investigated through Drain Current Transient (DCT) measurements and TCAD physics-based 2D device simulations. The DCT characterization reveals two prominent deep-level electron traps E1 (∼0.5 eV) and E2 (∼0.6 eV) in the AlGaN/GaN HEMT. The measured DCT spectrum is analyzed at different trap-filling pulse durations (10 µs–100 ms) to obtain the information of trapping kinetics. As the first step in the simulation, the TCAD physical model parameters are calibrated by matching the simulated DC characteristics with the experimental data. It is shown that the TCAD model incorporating the acceptor-type trap at EC – 0.5 eV in the GaN buffer quantitatively reproduces the measured DCT spectra over the temperature range of 25–100 °C. To explore the buffer trapping effects, the simulated DCT is inspected by varying the activation energy, capture cross section, and concentration of the buffer trap.

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In this work, thermoreflectance measurement technique is applied to GaN HEMTs transistors, GH15 8x50μm and 6x50μm from the UMS foundry. These measurements are compared to 3D simulation, but also to measurements based on an electrical approach we developed previously in [1]. The good agreement between results and the thermalization time constant proposed in [2] for GaN HEMTs validate finally all our approach dedicated to thermal resistance or thermal time constant