Papers by Author: Lin Zhu

Abstract: In this work, we have investigated triple and innovative multiple stacked contacts onto ptype SiC in order to evaluate whether or not there is any improvement in morphology or specific contact resistivity. The stacked metal contacts are based on Al, Ti and Ni with the specific contact resistivity measured at a low value of 5.02×10-6'cm2 for an Al(100 nm)/Ti(100 nm)/Al(10 nm) (where a “/” indicates the deposition sequence) triple stacked metal contact. XRD microstructural analysis and SEM measurements have been carried out and it has been discovered that the contacts, which formed the compound Ti3SiC2 at the metal/SiC interface, more readily display low-resistance ohmic characteristics after a post deposition anneal. Although the same amount of Ti (100 nm in total) has been deposited closer to the metal/SiC interface, none of the multiple stacked structures displayed ohmic behaviour after a post deposition anneal.

Abstract: We theoretically and experimentally compare the performance of a new JBS rectifier structure, the Buried Channel JBS (BC-JBS) rectifier, with that of the Lateral Channel JBS (LC-JBS) rectifier with 1.5kV blocking capability in 4H-SiC. The BC-JBS rectifier employs buried p-type regions to create a vertical JFET region to reduce the surface electric field at Schottky contact during reverse blocking while the LC-JBS rectifier adds a lateral channel together with the vertical JFET region to protect the surface Schottky interface during high-voltage blocking conditions. The LC-JBS rectifier offers low reverse leakage current while the BC-JBS rectifier demonstrates lower specific on-resistance. The optimized LC-JBS rectifiers show low forward drop (<1.8V) with PiN-like reverse characteristics.

Abstract: 4H-SiC PiN rectifiers with implanted anode and single-zone JTE were fabricated using AlN capped anneal. The surface damage during the high temperature activation anneal is significantly reduced by using AlN capped anneal. The forward drop of the PiN rectifiers at 100A/cm2 is 3.0V while the leakage current is less than 10-7A/cm2 up to 90% breakdown voltage at room temperature. With 6μm thick and 2×1016cm-3 doped drift layer, the PiN rectifiers can achieve near ideal breakdown voltage up to 1050V. Hole impact ionization rate was extracted and compared with previously reported results.

Abstract: For SiC devices capable of blocking very high voltages (>4kV), it becomes imperative to use bipolar devices because of unacceptably large on-state losses of unipolar devices. The IGBT offers the potential for high current density operation and ease of turn off using a MOS gate structure. In this work, 15kV 4H-SiC n-channel UMOS PT (Punch Through) IGBTs with injection enhancement effect near the top emitter and transparent pemitter structure at the collector have been demonstrated to have a forward drop approaching that of a PiN junction rectifier. With proper design, a PiN-like carrier distribution in the drift region can be achieved, which allows a better trade-off between collector-emitter saturation voltage (VCE(sat)) and turn-off loss (Eoff) than conventional SiC UMOS IGBTs.

Abstract: In this paper, the performance of high-voltage (10kV) 4H-SiC n- and p-channel IGBTs and n-channel MOS-Gated Bipolar Transistor (MGT) are investigated and compared using 2- dimensional numerical simulations. We have found that the MGT in SiC is not suitable for applications at high blocking voltages and the p-channel IGBT is a better choice because of a much higher conductivity modulation in the drift region.