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We report a novel noise analysis for the leakage current during time-dependent dielectric degradation under bias stress, illustrated using AlGaN/GaN superlattice castellated field-effect transistors (SLCFETs). Gate step stress is a standard approach to test the robustness of the gate dielectric in OFF-state conditions. Here, by removing the background step transients measured using a standard parameter analyzer, the algorithm gives a quantitative value for the nonstationary superimposed noise in the dielectric leakage current during the test. Extraction of the power spectrum using windowing and a direct fit to the noise statistical distribution gives the noise magnitude. Although the technique allows the monitoring of noise increase during stress, it is shown that this is insufficient to clearly identify irreversible degradation in these devices. An additional low bias noise test between each step-stress bias has been used to detect the onset of permanent localized breakdown. This is manifested as both a change in noise magnitude and frequency dependence, occurring before it can be seen in leakage current or direct noise measurements.

In this article, we investigate the impact of hard-switching on the dynamic ON-resistance ( ${R}_{ \mathrm{ ON}}$ ) in the AlGaN/GaN high-electron mobility transistors (HEMTs). The pulsed measurements were taken on a set of GaN-on-Si wafers, showing a significant ${R}_{ \mathrm{ ON}}$ increase after hard-switching compared with soft-switching. The impact of hard-switching was found to be strongly dependent on the surface passivation stoichiometry. Both hot electrons and self-heating are generated during hard-switching and they were investigated separately. For the self-heating effect, we found that the heating energy dissipated during hard-switching followed a different trend to the dynamic ${R}_{ \mathrm{ ON}}$ , showing that self-heating was not responsible for the dynamic ${R}_{ \mathrm{ ON}}$ . Following hard-switching, we found that the recovery of the ${R}_{ \mathrm{ ON}}$ occurred on a time scale of microseconds, far too fast to be explained by buffer trapping. Consequently, we suggest that the hard-switching-induced hot electrons are trapped on the surface and result in the dynamic ${R}_{ \mathrm{ ON}}$ . To support these conclusions, we undertook 2-D-TCAD simulations. Self-heating was found to be incompatible with the measurements, and surface-trapped hot electrons during hard-switching were shown to be consistent with the experimental observation. Based on the analysis, we find that modifying the field plates and stoichiometries of SiN x can be the possible solutions to suppress dynamic ${R}_{ \mathrm{ ON}}$ after hard-switching.

$\beta $ -Ga2O3 is an attractive material for high-voltage applications and has the potential for monolithically integrated RF devices. A combination of Raman nano-particle thermometry measurement and thermal simulation has been used to measure the peak channel temperature due to self-heating in $\beta $ -Ga2O3 MOSFETs. The peak channel thermal resistance measured at the gate surface in the device center was $88~mm\,\! \cdot \, K/W$ . This value is higher than what has been previously reported using electrical methods, which determine an average temperature over the whole device area. Experimentally validated thermal simulations have been used to propose possible thermal management mitigation approaches.

This paper reports on the impact of soft- and hard-switching conditions on the dynamic ON-resistance of AlGaN/GaN high-electron mobility transistors. For this study, we used a special double pulse setup, which controls the overlapping of the drain and gate waveforms (thus inducing soft and hard switching), while measuring the corresponding impact on the ON-resistance, drain current, and electroluminescence (EL). The results demonstrate that the analyzed devices do not suffer from dynamic ${R}_{ {\mathrm{\scriptscriptstyle ON}}}$ increase when they are submitted to soft switching up to ${V}_{{\text {DS}}}= 600$ V. On the contrary, hard-switching conditions lead to a measurable increase in the dynamic ON-resistance (dynamic- ${R}_{ \mathrm{\scriptscriptstyle ON}})$ . The increase in dynamic ${R}_{ \mathrm{\scriptscriptstyle ON}}$ induced by hard switching is ascribed to hot-electrons effects: during each switching event, the electrons in the channel are accelerated by the high electric field and subsequently trapped in the AlGaN/GaN heterostructure or at the surface. This hypothesis is supported by the following results: 1) the increase in ${R}_{ \mathrm{\scriptscriptstyle ON}}$ is correlated with the EL signal measured under hard-switching conditions and 2) the impact of hard switching on dynamic ${R}_{ \mathrm{\scriptscriptstyle ON}}$ becomes weaker at high-temperature levels, as the average energy of hot electrons decreases due to the increase scattering with the lattice.

This paper reports an experimental demonstration of the time-dependent failure of GaN-on-Si power high-electron-mobility transistors with p-GaN gate, submitted to a forward gate stress. By means of combined dc, optical analysis, and 2-D simulations, we demonstrate the following original results: 1) when submitted to a positive voltage stress (in the range of 7–9 V), the transistors show a time-dependent failure, which leads to a sudden increase in the gate current; 2) the time-to-failure (TTF) is exponentially dependent on the stress voltage and Weibull-distributed; 3) the TTF depends on the initial gate leakage current, i.e., on the initial defectiveness of the devices; 4) during/after stress, the devices show a localized luminescence signal (hot spots); the spectral investigation mainly reveals a peak corresponding to yellow luminescence and a broadband related to bremsstrahlung radiation; and 5) 2-D simulations were carried out to clarify the origin of the degradation process. The results support the hypothesis that the electric field in the AlGaN has a negligible impact on the device failure; on the contrary, the electric field in the SiN and in the p-GaN gate can play an important role in favoring the failure, which is possibly due to a defect generation/percolation process.

This paper reports an investigation of the trapping mechanisms responsible for the temperature-dependent dynamic- $R_{\mathrm {\mathrm{{\scriptstyle ON}}}}$ of GaN-based metal–insulator–semiconductor (MIS) high electron mobility transistors (HEMTs). More specifically, we perform the following. First, we propose a novel testing approach, based on combined OFF-state bias, backgating investigation, and positive substrate operation, to separately investigate the buffer- and the surface-related trapping processes. Then, we demonstrate that the dynamic $R_{\mathrm {\mathrm{{\scriptstyle ON}}}}$ of GaN-based MIS-HEMTs significantly increases when the devices are operated at high temperature levels. We explain this effect by demonstrating that it is due to the increased injection of electrons from the substrate to the buffer (under backgating conditions) and from the gate to the surface (under positive substrate operation). Finally, we demonstrate that by optimizing the buffer and by reducing the vertical leakage, substrate-related trapping effects can be completely suppressed. The results described within this paper provide general guidelines for the evaluation of the origin of dynamic $R_{\mathrm {\mathrm{{\scriptstyle ON}}}}$ in GaN power HEMTs and point out the important role of the buffer leakage in favouring the trapping processes.