In this paper, we characterize the signature of traps existing in the new AlGaN/GaN HEMT of 0.15-μm ultrashort gate length and 8 x 50 μm² gate width (GH15) through three different measurement techniques which are low frequency (LF) S-parameters, drain-current deep level transient spectroscopy (I-DLTS), and LF drain noise characterization. These three different measurements techniques were performed for varying chuck temperatures (Tchuck) ranging between 25 °C and 125 °C and for the same biasing condition. All measurements ensure approximatively the extraction of the same signature of traps [apparent activation energy (Ea) and cross section (σn)] existing in the UMS device. Furthermore, we have characterized the thermal resistance (RTH) using pulsed I-V measurement and a two-step calibration process. The determination of RTH is important to evaluate the device and to know precisely the signature of traps Ea and σn defined by the Arrhenius equation. A large signal measurements using an unequally spaced multitone (USMT) signal were done in order to evaluate the performance of GH15 transistor around the optimum load impedance in terms of efficiency (max PAE ~ 55%). The leakage current which measured before and after all measurements for VGS = -6, -7 V and for VDS varying from 0 to 10 V was lower than 100 μA/mm. To our knowledge, results on charge-trapping and large-signal performance are reported for the first time in 0.15-μm technology.

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 E_C –0.45 eV in the GaN buffer and surface donor states at E_C –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 E_C – 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.

We derived a simplified analytical expression to estimate the dynamic reduction in the 2DEG density due to the buffer trapping ( ${n}_{T}$ ) in GaN-based high-electron-mobility transistors (HEMTs). To compute ${n}_{T}$ , gate-lag drain current transient (DCT) measurements are carried out at a fixed temperature for different ${V}_{GS}$ points. The dynamic decrease in the 2DEG due to the Fe-related trap at ${E}_{C}$ -0.5 eV is found to be ~ $3.4\times10$ ¹¹ cm ⁻² in AlGaN/GaN HEMT; thus, ${n}_{T}$ is an essential quantity to evaluate the current collapse effects in HEMT. The validity of the expression is further demonstrated in the C-doped HEMTs. The calculated ${n}_{T}$ for the trap at ${E}_{C}$ -0.14 eV is about $9\times10$ ¹² cm ⁻⁰ in InAlN/GaN HEMT with C-doped buffer, and the calculated ${n}_{T}$ for the trap at ${E}_{C}$ -0.33 eV is ~ $1.2\times10$ ¹³ cm ⁻² in AlN/GaN HEMT with C-doped buffer. These values reveal that current collapse effects are more pronounced in the C-doped HEMTs than the Fe-doped HEMTs. Thus, this work is an important first step before further improvements in the model for computing buffer trap concentration.