This article deals with the characterization of charge trapping dynamics in a novel 100-nm double-heterojunction AlN/GaN/AlGaN-on-Si radio frequency (RF) HEMT process. In order to study the detrapping mechanisms, we perform the wideband acquisitions of the transient behavior by sweeping the pulsed voltages to cover the entire device operating area. The fast acquisition also enables the characterization of the charge capture behavior, a key aspect for RF performance. From the analysis of the drain current transients, time constants are extracted, showing a fundamental release time constant in the order of 0.1–1 ms, and more than one capture constants, the fastest being in the order of 300 ns. To the best of authors’ knowledge, this is the first time that trapping dynamics under large-signal regime are characterized for this type of process.

Charge trapping effects represent a major challenge in the performance evaluation and the measurement-based compact modeling of modern short-gate-length (i.e., ≤0.15 μm) Gallium Nitride (GaN) high-electron mobility transistors (HEMT) technology for millimeter-wave applications. In this work, we propose a comprehensive experimental methodology based on multi-bias large-signal transient measurements, useful to characterize charge-trapping dynamics in terms of both capture and release mechanisms across the whole device safe operating area (SOA). From this dataset, characterizations, such as static-IV, pulsed-IV, and trapping time constants, are seamlessly extracted, thus allowing for the separation of trapping and thermal phenomena and delivering a complete basis for measurement-based compact modeling. The approach is applied to different state-of-the-art GaN HEMT commercial technologies, providing a comparative analysis of the measured effects.

A generalized dual-input digital predistortion (DPD) methodology for supply-modulated (SM) power amplifiers (PAs) is proposed. Contrary to classical approaches, the SM and the radio frequency (RF) signals are treated as separate digital inputs to be jointly predistorted. A multi-objective optimization (MOO) strategy allows to explore the inherent PA performance tradeoffs to jointly optimize the DPD coefficients for improved power-added efficiency (PAE) and higher RF output power, yet guaranteeing a prescribed linearity performance. To avoid dealing with an unbearably high number of experimental acquisitions, MOO is here made feasible by fast simulation of an empirical surrogate model of the PA, which is progressively refined from a reduced set of iterative acquisitions. The proposed technique enables the adoption of a dynamic supply shaping function, and it automatically accounts for the signals' statistics. Eventually, the method outperforms classical SM approaches, yet using a DPD of the same order, as demonstrated by the experimental results on a gallium nitride (GaN) SM PA operating at 3.5 GHz in the presence of orthogonal-frequency-division-multiplexing (OFDM)-like high-peak-to-average power ratio (PAPR) modulated signals with 10- and 20-MHz bandwidths (BWs).

This work investigates wideband active load-pull (WALP) on microwave electron devices with a standard vector network analyzer (VNA), solely using calibrated frequency-domain relative measurements. Differently from the methods requiring full time-domain waveform acquisition capabilities, this approach removes any instantaneous bandwidth (BW) requirement, allowing to target modulated signals with arbitrarily large BWs. A VNA-based measurement setup is presented, and a novel mathematical framework is developed in order to enable the synthesis of an arbitrary wideband load profile using suitable numerical algorithms. A linear precompensation of the LS output match of the device, here implemented by different methods, is shown to significantly improve the speed and the stability of the basic secants' iterative method used to reach the target. Performance results, investigating the convergence properties of the approach and the effects of the setup dynamic range, are reported for a gallium nitride (GaN) high-electron-mobility transistor (HEMT) for up to 120-MHz output BW in the sub-6-GHz range.

This work describes a generalized multitone multiharmonic scattering parameters (M2S-parameters) measurement approach suitable for multiport nonlinear network characterization in the wave-variable domain. Based on the incommensurate (or offset) frequency concept, the M2S-parameters are directly measurable quantities independent of the incident wave phases and display a mild nonlinear dependence on the incident wave amplitudes. They feature a well-defined relationship with the frequency-domain nonlinear transfer functions derived from the Volterra theory, representing a generalization to the multiinput multiharmonic case of the widely used single-input single-frequency describing function approach. The proposed framework allows to capture the nonlinear steady-state behavior from a reduced set of measurements and can be effectively exploited for performance prediction in application-like scenarios. The approach is here applied to RF transistor and power amplifier load-pull measurements, as well as to the case of broadband modulation, showing that the performance assessment of the device can be obtained in a straightforward way from the M2S-parameters description.

Trapping effects of a state-of-the-art 100-nm GaN-on-Si high-electron mobility transistor (HEMT) process for radio-frequency (RF) applications are characterized for the first time. Considering an operation with high peak-to-average power ratio (PAPR) signals, pulsed-RF measurements give a more direct understanding of the dynamic trap behavior than the third-order intermodulation products (IM3). The experimental data are used for estimating the time constants describing the transients in the presence of signals with different PAPRs.