Investigation of lateral spreading current in the 4H-SiC Schottky barrier diode chip

Lateral current spreading in the 4H-SiC Schottky barrier diode (SBD) chip is investigated. The 4H-SiC SBD chips with the same vertical parameters are simulated and fabricated. The results indicate that there is a fixed spreading resistance at on-state in current spreading region for a specific chip. The linear specific spreading resistance at the on-state is calculated to be 8.6 Ω/cm in the fabricated chips. The proportion of the lateral spreading current in total forward current (P sp) is related to anode voltage and the chip area. P sp is increased with the increase in the anode voltage during initial on-state and then tends to a stable value. The stable values of P sp of the two fabricated chips are 32% and 54%. Combined with theoretical analysis, the proportion of the terminal region and scribing trench in a whole chip (K sp) is also calculated and compared with P sp. The K sp values of the two fabricated chips are calculated to be 31.94% and 57.75%. The values of K sp and P sp are close with each other in a specific chip. The calculated K sp can be used to predict that when the chip area of SiC SBD becomes larger than 0.5 cm2, the value of P sp would be lower than 10%.

SARS-CoV-2 Impairs Dendritic Cells and Regulates DC-SIGN Gene Expression in Tissues

The current spreading coronavirus SARS-CoV-2 is highly infectious and pathogenic. In this study, we screened the gene expression of three host receptors (ACE2, DC-SIGN and L-SIGN) of SARS coronaviruses and dendritic cells (DCs) status in bulk and single cell transcriptomic datasets of upper airway, lung or blood of COVID-19 patients and healthy controls. In COVID-19 patients, DC-SIGN gene expression was interestingly decreased in lung DCs but increased in blood DCs. Within DCs, conventional DCs (cDCs) were depleted while plasmacytoid DCs (pDCs) were augmented in the lungs of mild COVID-19. In severe cases, we identified augmented types of immature DCs (CD22+ or ANXA1+ DCs) with MHCII downregulation. In this study, our observation indicates that DCs in severe cases stimulate innate immune responses but fail to specifically present SARS-CoV-2. It provides insights into the profound modulation of DC function in severe COVID-19.

GEOMETRICAL ANALYSIS OF LIGHT-EMITTING DIODE FOR ENHANCING EXTRACTION EFFICIENCY

A non-uniform current spreading in the current spreader can greatly reduce the efficiency of the light-emitting diode (LED). The effects of the electrode contact area to the spreading layer towards extraction efficiency of LED chips is analysed in analytical simulations. Length of current spreading and light extraction efficiency is analysed for variation of contact area. The contact area value is varied by changing the shape of the electrode and the value of width of contact area. The increase in contact area decreases light extraction efficiency as more light are absorbed by the bottom electrode surface. The effective current spreading length for Indium Tin Oxide (ITO) of thickness 300nm is 36.44µm. The 6 strips ‘fork’ design is the most optimum. The design has the most area for photons produced in active region to escape without reducing the area cover with current density. This enables the chip to has more extraction efficiency with more uniform current spreading.