Modeling of high permittivity insulator structure with interface charge by charge compensation

An analytical model of the power metal–oxide–semiconductor field-effect transistor(MOSFET)with high permittivity insulator structure(HKMOS)with interface charge is established based on superposition and developed for optimization by charge compensation.In light of charge compensation,the disturbance aroused by interface charge is efficiently compromised by introducing extra charge for maximizing breakdown voltage(BV)and minimizing specific ON-resistance(R_(on,sp)).From this optimization method,it is very efficient to obtain the design parameters to overcome the difficulty in implementing the R_(on,sp)–BV trade-off for quick design.The analytical results prove that in the HKMOS with positive or negative interface charge at a given length of drift region,the extraction of the parameters is qualitatively and quantitatively optimized for trading off BV and Ron,sp with JFET effect taken into account.

Time-domain Finite Element Method for Transient Electric Field and Transient Charge Density on Dielectric Interface

This paper is devoted to solving the transient electric field and transient charge density on the dielectric interface under the electroquasistatic(EQS)field conditions with high accuracy.The proposed method is suitable for both 2-D and 3-D applications.Firstly,the governing equations represented by scalar electric potential are discretized by the nodal finite element method(FEM)in space and the finite difference method in time.Secondly,the transient constrained electric field equation on the boundary(TCEFEB)is derived to calculate the normal component of the transient electric field intensities on the Dirichlet boundary and dielectric interface as well as the transient charge density on the dielectric interface.Finally,a 2-D numerical example is employed to demonstrate the validity of the proposed method.Furthermore,the comparisons of the numerical accuracy of the proposed method in this paper with the existing FEMs for electric field intensity and charge density on the dielectric interface are conducted.The results show that the numerical accuracy of the proposed method for calculating the normal component of transient electric field intensities on the Dirichlet boundary and dielectric interface as well as the transient charge density on the dielectric interface is close to that of nodal electric potential and an order of magnitude higher than those of existing FEMs.

Performance enhancement of ZnO nanowires/PbS quantum dot depleted bulk heterojunction solar cells with an ultrathin Al_2O_3 interlayer

Depleted bulk heterojunction(DBH)PbS quantum dot solar cells(QDSCs),appearing with boosted short-circuit current density(J_(sc)),represent the great potential of solar radiation utilization,but suffer from the problem of increased interfacial charge recombination and reduced open-circuit voltage(V_(oc)).Herein,we report that an insertion of ultrathin Al_2O_3 layer(ca.1.2 A thickness)at the interface of ZnO nanowires(NWs)and Pb S quantum dots(QDs)could remarkably improve the performance of DBH-QDSCs fabricated from them,i.e.,an increase of V_(oc) from 449 mV to 572 mV,Jsc from21.90 mA/cm^2 to 23.98 mA/cm^2,and power conversion efficiency(PCE)from 4.29% to 6.11%.Such an improvement of device performance is ascribed to the significant reduction of the interfacial charge recombination rate,as evidenced by the light intensity dependence on Jsc and Voc,the prolonged electron lifetime,the lowered trap density,and the enlarged recombination activation energy.The present research therefore provides an effective interfacial engineering means to improving the overall performance of DBH-QDSCs,which might also be effective to other types of optoelectronic devices with large interface area.

Optimization of junction termination extension for ultrahigh voltage 4H-SiC planar power devices

Numerical simulations on the optimization of junction termination extension(JTE) have been performed.Various termination techniques have been applied and simulated in this paper,such as single-zone JTE(S-JTE),multi-zone JTE(M-JTE),and space-modulated JTE(SM-JTE).A completely novel and efficient method is demonstrated in this paper to determine total length of SM-JTE,and it is verified through simulation results.The simulation results show that the SM-JTE could provide a protection efficiency(defined in Section 2) of 95.2%,which is much higher than that of M-JTE(82.4%) and S-JTE(64.7%).Based on the fabricated MOSFETs,the interface charge density is extracted and the approximate range of charge density has been determined.The influences of different interface charge densities have been investigated for the three termination techniques respectively.According to the previous reports,the JTE is quite sensitive to the implanted dose,so the blocking capability of each termination structure with different implanted doses is also simulated.The results show that when interface charge is considered,the SM-JTE always shows an enormous advantage over the other two junction termination structures,however the interface charge densities varied.The space-modulated JTE is also applicable to the power planar devices such as MOSFETs and IGBTs,which would provide a very promising lower fabrication cost.

Improving solar control of magnetism in ternary organic photovoltaic system with enhanced photo-induced electrons doping

§The growing demand for storage space has promoted in-depth research on magnetic performance regulation in an energy-saving way.Recently,we developed a solar control of magnetism,allowing the magnetic moment to be manipulated by sunlight instead of the magnetic field,current,or laser.Here,binary and ternary photoactive systems with different photon-to-electron conversions are proposed.The photovoltaic/magnetic heterostructures with a ternary system induce larger magnetic changes due to higher short current density(J SC)(20.92 mA·cm^(−2))compared with the binary system(11.94 mA·cm^(−2)).During the sunlight illumination,ferromagnetic resonance(FMR)shift increases by 80%(from 169.52 to 305.48 Oe)attributed to enhanced photo-induced electrons doping,and the variation of saturation magnetization(M S)is also amplified by 14%(from 9.9%to 11.3%).Furthermore,photovoltaic performance analysis and the transient absorption(TA)spectra indicate that the current density plays a major role in visible light manipulating magnetism.These findings clarify the laws of sunlight control of magnetism and lay the foundation for the next generation solar-driven magneto-optical memory applications.