4H-SiC Drift Step Recovery Diode with Super Junction for Hard Recovery

Silicon carbide (SiC) drift step recovery diode (DSRD) is a kind of opening-type pulsed power device with wide bandgap material. The super junction (SJ) structure is introduced in the SiC DSRD for the first time in this paper, in order to increase the hardness of the recovery process, and improve the blocking capability at the same time. The device model of the SJ SiC DSRD is established and its breakdown principle is verified. The effects of various structure parameters including the concentration, the thickness, and the width of the SJ layer on the electrical characteristics of the SJ SiC DSRD are discussed. The characteristics of the SJ SiC DSRD and the conventional SiC DSRD are compared. The results show that the breakdown voltage of the SJ SiC DSRD is 28% higher than that of the conventional SiC DSRD, and the dv/dt output by the circuit based on SJ SiC DSRD is 31% higher than that of conventional SiC DSRD. It is verified that the SJ SiC DSRD can achieve higher voltage, higher cut-off current and harder recovery characteristics than the conventional SiC DSRD, so as to output a higher dv/dt voltage on the load.

Effect of Electric Field Regulation on Laser Damage of Composite Low-Dispersion Mirrors

Low dispersion mirrors are important because of their potential use in petawatt (PW) laser systems. The following two methods are known to increase the laser-induced damage threshold of low dispersion optical components: use of a wide-bandgap-material protective layer and control of electric field distribution. By controlling the electric field distribution of composite low-dispersion mirrors (CLDM), we shift the electric field peaks from the material interface into the wide-bandgap material. However, the damage threshold of modified-electric-field composite low dispersion mirror (E-CLDM) does not increase. Damage morphology shows that the initial damaged layer is Ta2O5. An immediate cause is the enhancement of the electric field in internal layers caused by surface electric field regulation. Theoretical calculations show that the damage threshold of CLDM or E-CLDM is determined by the competition results of bandgap and the electric field of layer materials. The CLDM with different materials or different protective layer periods can be optimally designed according to the electric field competition effect in the future.

Study of Eutectic Etching Process for Defects Analysis in n type 4H SiC

Silicon Carbide (SiC) is a wide bandgap material with unique properties attractive for high power, high temperature applications. The presence of defects in the crystal is a major issue prior device fabrication. These defects affect the performance of the device. To delineate and identify the defects an easy and quick method is desirable. In this study defects delineation in n-type 4H-SiC has been carried out by KOH, KOH+NaOH and KOH+Na2O2 melts. Variation in etch pits size was found at various concentrations of the NaOH in KOH and for different total etching times in the KOH+Na2O2 melt. The eutectic solution etching technique is found to be more efficient to delineate defects and provides control on etching and surface roughness. The etching rates have been estimated under different experimental conditions. Detailed morphological investigations have been performed by wide field high resolution optical microscopy and scanning electron microscopy.

Midgap radiative centers in carbon-enriched hexagonal boron nitride

When serving as a protection tissue and/or inducing a periodic lateral modulation for/in atomically thin crystals, hexagonal boron nitride (hBN) has revolutionized the research on van der Waals heterostructures. By itself, hBN appears as an emergent wide-bandgap material, which, importantly, can be optically bright in the far-ultraviolet range and which frequently displays midgap defect-related centers of yet-unclear origin, but, interestingly, acting as single-photon emitters. Controlling the hBN doping is of particular interest in view of the possible practical use of this material. Here, we demonstrate that enriching hBN with carbon (C) activates an optical response of this material in the form of a series of well-defined resonances in visible and near-infrared regions, which appear in the luminescence spectra measured under below-bandgap excitation. Two, qualitatively different, C-related radiative centers are identified: One follows the Franck–Condon principle that describes transitions between two defect states with emission/annihilation of optical phonons, and the other shows atomic-like resonances characteristic of intradefect transitions. With a detailed characterization of the energy structure and emission dynamics of these radiative centers, we contribute to the development of controlled doping of hBN with midgap centers.

First Principles Research on the Magnetic Properties of Na and Cl doped ZnO

ZnO is considered as a wide bandgap material because it has a 3.4 eV direct bandgap. This wide bandgap characteristic causes good transparency, high electron mobility and luminescence at room temperature.The unique and tuneable properties of nanostructured ZnO shows excellent stability in chemically as well as thermally stable n-type semiconducting material with wide applications such as in luminescent material, supercapacitors, battery and solar cells. To be applied to a variety of needs, price control bandgap is needed. Likewise, control over the magnetic nature. Therefore we need a study related to bandgap modification, one of them is by giving impurity atoms. Atom Na and Cl were chosen as representatives of donors and acceptors. Atomistic calculations use the Functional Density Theory method which is implemented in ABINIT software. Relaxation and convergence research results are used to find the most stable energy value of ZnO.. The results showed Magnetic Properties in ZnO doping Na obtained magnetization values of 1.4802 𝜇𝐵 greater than pure ZnO that is 0.9394 𝜇𝐵 while ZnO doping Cl obtained magnetization values of 0.8593 𝜇𝐵 smaller than pure ZnO. In conclusion the ZnO doping magnetic properties of Na increase magnetization and Cl doping also change the magnetic properties by decreasing ZnO magnetization.