Search

A novel high performance SiC asymmetric cell trench MOSFET with split gate (SG) and integrated junction barrier schottky (JBS) diode (SGS-ATMOS) is proposed for the first time. The shielding effect provided by the SG structure not only reduces the gate-drain capacitance ( ${C}_{\mathrm{gd}}$ ) but also alleviates the electric field crowding in the dielectric layer at trench corner. The integrated trench JBS diode bypasses the PiN body diode while obtaining good double protection from the SG and p-type shielding region. Therefore, not only the MOSFET but also diode performance is significantly improved for the proposed structure. Numerical analysis results show that compared with the conventional asymmetric cell trench MOSFET (Con-ATMOS), the high frequency figure of merit (HFFOM1, ${R}_{\mathrm{on}} {\cdot } {C}_{\mathrm{gd}}$ ) is reduced by 92.5% and the Baliga figure of merit (BFOM, ${BV}^{2}/R_{\mathrm{on,sp}}$ ) is increased by 57.2%, respectively. In addition, the forward conduction voltage drop ( ${V}_{\mathrm{F}}$ ), reverse recovery charge ( ${Q}_{\mathrm{rr}}$ ) and peak reverse recovery current ( ${I}_{\mathrm{rrm}}$ ) of the diode are reduced from 3.10V, $1.95\mu \text{C}$ /cm2 and 68.0A for the Con-ATMOS to 1.56V, $0.97\mu \text{C}$ /cm2 and 35.9A for the proposed SGS-ATMOS, respectively. Compared with the Con-ATMOS, the turn-on loss ( ${E}_{\mathrm{on}}$ ) and turn-off loss ( ${E}_{\mathrm{off}}$ ) of the proposed device are reduced by 33.3% and 33.0%, respectively. The ${E}_{\mathrm{on}}$ and ${E}_{\mathrm{off}}$ of the proposed device are also 33.6% and 30.0% off compared with the Con-ATMOS with external JBS diode, respectively. The temperature characteristics of the SGS-ATMOS are also discussed and it is found that the proposed device exhibits good performance at high temperature.

Variations in precipitation and atmospheric N deposition affect water and N availability in desert and thus may have significant effects on desert ecosystems. Haloxylon ammodendron is a dominant plant in Asian desert, and addressing its physiological acclimatization to the changes in precipitation and N deposition can provide insight into how desert plants adapt to extreme environments by physiological adjustment. Carbon isotope ratio (δ13C) in plants has been suggested as a sensitive long-term indicator of physiological acclimatization. Therefore, this study evaluated the effect of precipitation change and increasing atmospheric N deposition on δ13C of H. ammodendron. Furthermore, H. ammodendron is a C4 plant; whether its δ13C can indicate water use efficiency (WUE) has not been addressed. In the present study, we designed a field experiment with a completely randomized factorial combination of N and water and measured δ13C and gas exchange of H. ammodendron. Then we calculated the degree of bundle-sheath leakiness (φ) and WUE of the assimilating branches of H. ammodendron. δ13C and φ remained stable under N and water supply, while N addition, water addition and their interaction affected gas exchange and WUE in H. ammodendron. In addition, δ13C had no correlation with WUE. These results were associated with the irrelevance between δ13C and the ratio of intercellular to ambient CO2 concentration (ci / ca), which might be caused by a special value (0.37) of the degree of bundle-sheath leakiness (φ) or a lower activity of carbonic anhydrase (CA) of H. ammodendron. In conclusion, δ13C of H. ammodendron is not sensitive to global change in precipitation and atmospheric N deposition and cannot be used for indicating its WUE.

Variations in precipitation and atmospheric N deposition affect water and N availability in desert, and thus may have significant effects on desert ecosystems. Haloxylon ammodendron is a dominant plant in Asian desert, and addressing its physiological acclimatization to the changes in precipitation and N deposition can provide an insight into how desert plants adapt extreme environment by physiological adjustment. Carbon isotope ratio (ẟ13C) in plants has been suggested as a sensitive long-term indicator of physiological acclimatization. Therefore, this study evaluated the effect of precipitation change and increasing atmospheric N depositon on ẟ13C of H. ammodendron. Furthermore, Haloxylon ammodendron is a C4 plant, whether its ẟ13C can indicate water use-efficiency (WUE) has not been addressed. In the present study, we designed a field experiment with a completely randomized factorial combination of N and water, and measured ẟ13C, gas exchange and WUE of the assimilating branches of H. ammodendron. ẟ13C in H. ammodendron remained stable under N and water supply, while N addition, water addition and their interaction affected gas exchange and WUE in H. ammodendron. In addition, ẟ13C had no correlation with WUE. This result are associated with the irrelevance between ẟ13C and ci/ca, which might be caused by a special value (0.37) of the degree of bundle-sheath leakiness (φ) or a lower activity of carbonic anhydrase (CA) of H. ammodendron. Thus, ẟ13C of H. ammodendron cannot be used for indicating its WUE.

A novel high performance snapback-free reverse-conducting insulated gate bipolar transistor with silicon/silicon carbide (Si/SiC) heterojunction (HJ-RC-IGBT) is proposed for the first time. The formed heterojunction in the collector for the proposed structure cuts off the current flow path of the internal parasitic MOSFET in the IGBT mode. The simulation results show that similar as the conventional FS-IGBT, a snapback-free current-voltage (I-V) characteristics is achieved without using a large p-collector width. Therefore, compared to the conventional RC-IGBT and FS-IGBT, the tradeoff relationship between the on-state voltage drop $(V_{\mathrm{c}\mathrm{e}(\mathrm{o}\mathrm{n})})$ and turn-off loss $(E_{\mathrm{o}\mathrm{f}\mathrm{f}})$ is improved for the proposed HJ-RC-IGBT. Meanwhile, the distribution of current and carriers are uniform for the proposed HJ-RC-IGBT in both IGBT and diode modes, which improves the device reliability.