Foreword to the special issue on wide-bandgap(WBG)semiconductors:from fundamentals to applications

The development of new kinds of semiconductor material is a very attractive topic of scientific research and appliations.Graphene is considered as one of the most impressive 2D materials for many applications,like graphene-reinforced metal matrix nanocomposites.1 Widebandgap(WBG)semiconductors have received widespread attention in recent years because of their superior physical properties such as large band gap,high carrier mobility,and high thermal conductivity.Represented by silicon carbide(SiC)and gallium nitride(GaN),WBG semiconductor materials,therefore,can be operated in extreme working environments or conditions such as high temperature,high frequency,and high power.

Improvement on short-circuit ability of SiC super-junction MOSFET with partially widened pillar structure

A novel 1200 V SiC super-junction(SJ)MOSFET with a partially widened pillar structure is proposed and investi-gated by using the two-dimensional numerical simulation tool.Based on the SiC SJ MOSFET structure,a partially widened P-region is added at the SJ pillar region to improve the short-circuit(SC)ability.After investigating the position and doping concentration of the widened P-region,an optimal structure is determined.From the simulation results,the SC withstand times(SCWTs)of the conventional trench MOSFET(CT-MOSFET),the SJ MOSFET,and the proposed structure at 800 V DC bus voltage are 15μs,17μs,and 24μs,respectively.The SCWTs of the proposed structure are increased by 60%and 41.2%in comparison with that of the other two structures.The main reason for the proposed structure with an enhanced SC capability is related to the effective suppression of saturation current at the high DC bias conditions by using a modu-lated P-pillar region.Meanwhile,a good Baliga's FOM(BV^(2)/R_(on))also can be achieved in the proposed structure due to the advantage of the SJ structure.In addition,the fabrication technology of the proposed structure is compatible with the standard epitaxy growth method used in the SJ MOSFET.As a result,the SJ structure with this feasible optimization skill presents an effect on improving the SC reliability of the SiC SJ MOSFET without the degeneration of the Baliga's FOM.

A boronate-modified renewable nanointerface for ultrasensitive electrochemical assay of cellulase activity

The saccharification of cellulosic biomass to produce biofuels and chemicals is one of the most promising industries for gree n-power production and sustainable development.Cellulase is the core component in the saccharification process.Simple and efficient assay method to determine cellulase activity in saccharification is thus highly required.In this work,a boronate-affinity surface based renewable and ultrasensitive electrochemical sensor for cellulase activity determination has been fabricated.Through bo ronate-sugar interaction,celluloses are attached to the electrode surface,forming the cellulose na nonetwork at the sensing interface.Cellulase degradation can lead to the variation of electrochemical impedance.Thus,electrochemical impedance signal can reflect the cellulase activity.Importantly,via fully utilizing the boronate-affinity chemistry that enables reversible fabrication of cellulose nanonetwork,a renewable sensing surface has been firstly constructed for cellulase activity assay.Thanks to interfacial diffusion process of electrochemical sensor,the product inhibitory effect in the cellulase activity assays can be circumvented.The proposed electrochemical sensor is ultrasensitive for label-free cellulase activity detection with a very simple fabrication process,showing great potential for activity screen of new enzymes in saccharification conversion.