A new vertical geometry photoconductive switch device based on vanadium compensated 4H Silicon Carbide (4H-SiC) is presented with the structure of aluminum doped ZnO (AZO) transparent conductive window on the top of 4H-SiC and a silver mirror reflector on the backside. For this new structure, laser can trigger the device conveniently by irradiate the electrode face directly. A circuit without load resistor is used to test the performance of device, and a switch is triggered by Nd:YAG 532-nm laser (10-ns full-width at half-maximum). Results show that the minimum on-state resistance is 7.5 Ω at an illumination density of 18.2 MW/cm², and the breakdown voltage is 12 kV (breakdown electric field is 260 kV/cm). In particular, the optical utilization efficiency of laser energy and the minimum on-state resistance performance are significantly improved in this new vertical geometry photoconductive switch by the AZO film and mirror reflector.

Molecular dynamic (MD) simulations were used to study threshold displacement energy (TDE) surface and Si displacement cascades in 4H-SiC system. To figure out the role of different Wyckoff sites in determining the TDE values, both Si and C atoms in 2a and 2b Wyckoff sites were separately considered as the primary knocked atoms (PKA). The initial kinetic energy was then distributed along 146 different crystallographic directions at 10 K. TDE surface appeared highly anisotropic for Si and C displacements along different crystallographic directions. The TDE was determined as 41 eV for Si and 16 eV for C. The average values of TDE over two Wyckoff sites were estimated to 66 eV for Si PKA and 24 eV for C PKA. The displacement cascades produced by Si recoils of energies spanning varied from 5 keV to 50 keV at 300 K. To count the number of point defects using Voronoi cell analysis method, the crystal structure of 4H–SiC was transformed from hexagonal to orthorhombic. It was found that the surviving defects at the end of cascades were dominated by C vacancies and interstitials due to low displacement energies of C atoms and greater number of C interstitials when compared to C vacancies.

In this work, the effects of the SiO_x interface layer grown by exposure in air on the performance of planar hybrid n-Si/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solar cells are investigated. Compared to the cell with a hydrogen-terminated Si surface, the cell with an oxygen-terminated Si surface reveals improved characteristics in power conversion efficiency, increased from 10.44% to 13.31%. By introducing the SiO_x, the wettability of the Si surface can be improved, allowing an effective spread of the PEDOT:PSS solution and thus a good contact between the PEDOT:PSS film and Si. More importantly, it can change the polarity of the Si surface from a negative dipole to a positive dipole, owing to the introduction of the SiO_x interface. The Si energy band will bend up and give rise to a favorable band alignment between Si and PEDOT:PSS to promote carrier separation. These results could be potentially employed to further development of this simple, low-cost heterojunction solar cell.

Strains in graphene play a significant role in graphene-based electronics, but many aspects of the grain boundary effects on strained graphene remain unclear. Here, the relationship between grain boundary and strain property of graphene grown by chemical vapor deposition (CVD) on the C-face of SiC substrate has been investigated by Raman spectroscopy. It is shown that abundant boundary-like defects exist in the graphene film and the blue-shifted 2D-band frequency, which results from compressive strain in graphene film, shifts downward linearly as 1/L_a increases. Strain relaxation caused by grain boundary diffusion is considered to be the reason and the mechanism is analyzed in detail.

Silicon Carbide (SiC) Ultraviolet (UV) phototransistors with bidirectional bias response were fabricated and analyzed in this letter. The results showed that the fabricated UV phototransistor exhibited stable photoelectric response characteristics and transistor characteristics under both forward and reverse voltages, owing to the structure design of the epi-layers, while the mechanism of the bidirectional response was also studied. The difference in photocurrent under different bias voltages and wavelengths of UV illumination were mainly due to the variation of the absorption coefficient with wavelength and the change in the width of the space charge regions, which ultimately led to a difference in the number of photo-generated carriers. The time response characteristics of the detector showed that there were time delays when the detector was turned on and turned off, which was caused by the photo minority carriers in the depletion layer of the base-collector junction.

Silicon carbide (SiC) ultraviolet (UV) phototransistors with normal operation up to 550 °C were fabricated and analyzed in this article. Under 280 nm UV illumination, the responsivity has reached 0.016 and 0.13 A/W at room temperature (RT) and 400 °C, respectively. In addition, the responsivity showed a trend of increasing and then decreasing with rising temperature, and reaching a peak at 400 °C. This phenomenon suggested that there might be an optimal detection temperature for SiC UV phototransistor detectors (PTDs), and this temperature could be tuned by changing the physical parameters of the device. Moreover, this property could be exploited in reverse for the estimation of the temperature range. The transient response characteristics of the detector showed that there was a hysteresis at shutdown, which was caused by the increase of the electron and hole density with temperature to increase the capacitance of the p-n junction depletion layer, resulting in deterioration of frequency characteristics. This work is significant for developing high-temperature 4H-SiC-based UV PDs.