Current Issue : April-June Volume : 2023 Issue Number : 2 Articles : 5 Articles
This study proposed a novel 4H-SiC double trench metal-oxide-semiconductor field-effecttransistor (DTMCD-MOSFET) structure with a built-in MOS channel diode. Further, its characteristics were analyzed using TCAD simulation. The DTMCD-MOSFET comprised active and dummy gates that were divided horizontally; the channel diode operated through the dummy gate and the p-base and N+ source regions at the bottom of the dummy gate. Because the bult-in channel diode was positioned at the bottom, the DTMCD-MOSEFT minimized static deterioration. Despite having a 5.2% higher specific on-resistance (Ron-sp) than a double-trench MOSFET (DT-MOSFET), the DTMCDMOSFET exhibited a significantly superior body diode and switching properties. In comparison to the DT-MOSFET, its turn-on voltage (VF) and reverse recovery charge (Qrr) were decreased by 27.2 and 30.2%, respectively, and the parasitic gate-drain capacitance (Crss) was improved by 89.4%. Thus, compared with the DT-MOSFET, the total switching energy loss (Etot) was reduced by 41.4%....
Novel 1.7-kV 4H-SiC trench-gate MOSFETs (TMOSFETs) with a grid pattern and a smaller specific on-resistance are proposed and demonstrated via numerical simulations. The proposed TMOSFETs provide a reduced cell pitch compared with TMOSFETs with square and stripe patterns. Although TMOSFETs with a grid pattern reduce the channel area by approximately 10%, the cell density is increased by approximately 35%. Consequently, the specific on-resistance of the grid pattern is less than that of the square and stripe patterns. The forward blocking characteristics of the grid pattern are increased by the reduced impact ionization rate at the P/N junction. As a result, the figure-of-merit (FOM) of the grid pattern is increased by approximately 33%....
Light-emitting diodes (LEDs) are of interest for implementation in radiation environments, such as part of illumination systems of radiation-tolerant cameras able to provide images at high doses (>MGy). It is then mandatory to characterize the radiation effects on all of the LED key properties exploited for such applications. To this aim, the evolution of the optical properties of commercial LEDs after they have been exposed to γ-rays, up to total ionizing dose (TID) levels of 2 MGy(air) at room temperature, is discussed. The devices under test include four LEDs of different colors (red, green, blue and white) in the same package. This allows a direct comparison between the responses of the different structures and technologies, as the proximity between the diodes ensures the uniformity of their irradiation conditions. The radiation effect on the electron–photon conversion mechanisms inside these LEDs is investigated through the evolution of their external quantum efficiency (EQE) vs. current characteristics. The spectral emission pattern of LEDs after irradiation at different dose levels is then characterized to estimate the TID effects on the lens which surrounds the LED package. The presented results show a monotone radiation-induced EQE decrease as a function of the TID, especially in the red LEDs. For the tested red LEDs, the EQE decreased up to 78% after a TID of 1 MGy when they were OFF during irradiation, and up to 8% when they were ON during irradiation. A visual inspection of the devices after irradiation shows a mechanical degradation of the lens shared among the four diodes. However, the emission pattern analysis does not show any significant radiation-induced changes in the optical properties of the lens. Based on these results, it appears possible to design LED-based illumination systems able to survive to MGy dose levels that can be integrated as subsystems of radiation-hardened cameras....
We demonstrated efficient simplified orange and white organic light-emitting devices based on a platinum(II) complex Tetra-Pt-N. The maximum current efficiency achieved from the optimized orange device was 57.6 cd/A. The emission mechanism for the system of Tetra-Pt-N doped into 4,4’-bis(arbazole-9-yl)biphenyl was discussed. Moreover, a high-efficiency and simplified white device was fabricated by introducing an ultra-thin blue phosphorescent emission layer. The white device with a maximum current efficiency of 41.9 cd/A showed excellent stable spectra and low efficiency roll-off....
The advent of the point-contact transistor is one of the most significant technological achievements in human history with a profound impact on human civilization during the past 75 years. Although the first transistor was made of germanium it was soon replaced by silicon, a material with lower intrinsic carrier mobilities but with a substantially better native oxide. Interestingly, more than two decades ago, germanium was once again considered as a mainstream microelectronic material, since the introduction of high-k dielectrics allowed the consideration of channel materials irrespective of the quality of their native oxide. After about 50 years of limited studies on the defect processes in germanium, the community once again focused on its applicability for mainstream electronic applications. Nevertheless, there are some bottlenecks that need to be overcome, and it was the aim of the present review to discuss the progress in the understanding of the defect processes of Ge....
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