Davide Maria Lombardo

An experimental and numerical study of the on-resistance degradation in AlGaN/GaN-based technology is presented. Back-bias measurements on transmission-line-method (TLM) structures were performed to investigate the mechanism underlying the current degradation. The observed TLM current collapse exhibits Arrhenius behavior, which is associated with traps in the buffer layers. Interestingly, the decay time of the collapse shows a decreasing trend with increasing applied bias, which is here investigated and newly interpreted as a signature of Poole–Frenkel bias-enhanced trap emission. An effective model is discussed and implemented in TCAD simulations to support the experimental findings. In addition to providing justification for the temperature and applied-voltage dependence of the observed degradation trends, the proposed mechanism can also explain the spread in the activation energies measured for acceptor traps in the buffer layers, as reported in the literature for AlGaN/GaN technologies.

In this work, we present a comprehensive analysis of the back-effect phenomenon in Schottky p-GaN gate AlGaN/GaN high-electron-mobility transistors (HEMTs). By investigating different device structures, we emphasize the critical role played by the gate terminal in the device’s performance. Our study focuses on two main factors that significantly impact the current degradation caused by the back-effect: the magnesium (Mg) concentration in the p-GaN layer and gate polarization (V ${}_{\text {GS}}\text {)}$ . Finally, we propose a physics-based model supported by experimental data to provide further insights and details into this phenomenon, providing important indication to find the best tradeoff in the development of GaN HEMTs operating in monolithic half-bridge configuration.

In this brief, we investigate the correlation between dynamic- ${Q}_{\text {OSS}}$ and dynamic- ${R}_{\text {ON}}$ of 650-V packaged AlGaN/GaN high-electron-mobility transistors (HEMTs). To this end, a novel measurement setup is proposed to evaluate the on-the-fly evolution of both parameters during conventional switch-mode operations. The measurements performed at ${V}_{\text {DS}} =200$ V show that the dynamic- ${R}_{\text {ON}}$ and dynamic- ${Q}_{\text {OSS}}$ present similar exponential transients and time constants, potentially explained by the ionization of C-related acceptors in the GaN buffer. The same activation energy ( ${E}_{\text {A}}\text {)}$ has been observed for both ${Q}_{\text {OSS}}$ and ${R}_{\text {ON}}$ , suggesting that their drifts are related to the same physical mechanism. The characterization has also been performed at different ${V}_{\text {DS}}$ levels, indicating that the observed correlation holds in the entire range up to 520 V.

The measurement of Higgs couplings constitutes an important part of present standard model precision tests at colliders. We show that modifications of Higgs couplings induce energy-growing effects in specific amplitudes involving longitudinally polarized vector bosons, and we initiate a novel program to study these effects off shell and at high energy, rather than on the Higgs resonance. Our analysis suggests that these channels are complementary and competitive with familiar on-shell measurements; moreover, they offer endless opportunities for refinement and improvements.