This work investigates the degradation mechanism of 1.2 kV silicon carbide (SiC) metal oxide semiconductor field-effect transistor (MOSFET) under positive or negative long-term high-temperature gate bias (HTGB) stress. After positive long-term HTGB stress, the device shows a positive shift in threshold voltage ( ${V}_{\text {th}}{)}$ and an increase in ON-state resistance ( ${R}_{ \mathrm{\scriptscriptstyle ON}}{)}$ , which mainly results from the electron traps at or near the SiC/SiO2 interface. While subjected to negative HTGB stress, the drift of $V_{\text {th}}$ is time-dependent and correlated with the gate bias. For the device biased at a low gate voltage of −10 V, due to the hole traps at or near the interface, its ${V}_{\text {th}}$ exhibits negative shift all the time. But the drift of ${V}_{\text {th}}$ for the device biased at a higher voltage of −20 V is decreased first with the stress time, then is increased with the stress time, which may result from the hole traps and the additional electron traps introduced by the tunneling effect. Through the low-frequency noise technology, it is demonstrated that the trap density of the device biased at higher negative gate voltage of −20 V has been increased up to three times.

In this article, an innovative layout is introduced to reduce the stray inductance of the multichip power modules (MCPMs) through reverse coupling of current in parallel power loops, which effectively cancels out mutual inductance. A half-bridge silicon carbide (SiC) MOSFET power module was designed based on this novel layout. The fabricated SiC power module was experimentally validated, demonstrating a measured stray inductance of about 3.5 nH. Experimental results confirmed that the proposed module outperforms counterpart commercial SiC MOSFET power modules in terms of turn-off overshoot voltage and switching loss reduction, highlighting the advantage of the reverse-coupling current approach in enhancing power module performance. The principle of enhancing negative mutual inductance and dynamic current sharing in circuits through the reverse coupling parallel loops is discussed.

The long-term reliability of the commercially available vertical-cavity surface-emitting laser (VCSEL) at 1310 nm wavelength is investigated. To do so, a high current accelerated life test is used to evaluate the 1310 nm VCSEL reliability. Variations of properties that depend on the operating condition are characterized by the light-current-voltage, leakage current and low-frequency noise. When the aging current is 6 mA, 8 mA and 10 mA, the maximum output power reduces by 5%, 6% and 15% of the initial value, respectively. It is demonstrated theoretically and experimentally that the leakage current increases and reverse bias breakdown voltage decreases after the accelerated current aging test. The current noise power spectral density increases after the device ages, and the noise increases with the augment of the electrical stress. When the bias current of VCSEL is below the threshold, the frequency index factor and noise amplitude gradually increase with the bias current increase. Further, lifetime fitting curves of the devices at an accelerating current of 6 mA, 8 mA and 10 mA are obtained, and the median lifetime of 67 years at the operating current is extrapolated.

Light-emitting diode (LED) drivers are widely regarded as the weakest link in the solid-state lighting (SSL) systems. This paper considers its system-level reliability metrics based on component-level. The proposed method considers the parameter variations in both the stress levels and the lifetime model of electrolytic capacitors while assessing the reliability of LED drivers. To be specific, for evaluating the uncertainties of component thermal stress, system-level finite element (FE) thermal simulation is firstly carried out in ANSYS icepak. Then, the fluctuations of capacitor's hotspot temperature, are calculated according to the change of environment temperature. On the other hand, uncertainties of the life-stress model can be obtained by accelerated lifetime testing. Afterwards, the reliability block diagram of the LED driver is used to evaluate the reliability of the LED driver. By using Monte Carlo simulation, the Weibull lifetime distribution of components and the LED driver, as well as their B ₁ and B ₁₀ lifetime can be obtained according to component-level reliability. In a case study of an LED driver for street lighting, the parameters of lifetime distribution and reliability curves prove that the input electrolytic capacitor is the fragile components in the LED driver. The results can guide a heat-dissipation trade-off between the manufacturer cost and reliability constraint.