In this study, we proposed β-Ga₂O₃ JFET using nitrogen doping and analyzed the electrical characteristics. In β-Ga₂O₃, nitrogen ions act as a deep acceptor and are used to implement the current blocking layer. By using this characteristic of the nitrogen ion, in the proposed JFET, nitrogen ions are used to obtain gate control and pinch off the channel of the JFET. The numerical TCAD simulation was performed to design and analyze the proposed JFET. The simulated forward and reverse characteristics of the proposed JFET were obtained as a function of JFET width and nitrogen doping concentration. The maximum breakdown voltage of 1.7 kV was obtained with the on-resistance of 16.7 mΩ·cm² when the channel width was 1.5 μm and nitrogen doping concentration is 1×1018/cm³, respectively.

We investigated the potential of IO:H thin films and hydrogen doping to improve current density and fill factor for enhancing the performance of silicon heterojunction solar cells. We revealed that a transmittance of 86.7% and work function of 5.4 eV could be achieved by injecting 3 sccm of hydrogen gas. The lattice constant of 1.037 nm at the AB site indicates an anion antibonding tendency, and the work function increases as the Fermi level shifts to the valence band. Based on these findings, we fabricated a silicon heterojunction solar cell and achieved an efficiency of 18.53%, while computer simulation confirmed a conversion efficiency of 24.65%, an open-circuit voltage of 724 mV, and a fill factor of 82.72% at a current density of 41.15 mA/㎠.

High-energy bandgap material silicon carbide (SiC) is gaining attention as a next-generation power semiconductor material, and in particular, SiC-based MOSFETs are developed as representative power semiconductors to increase the breakdown voltage (BV) of conventional planar structures. However, as the size of SJ (Super Junction) MOSFET devices decreases and the depth of pillars increases, it becomes challenging to uniformly form the doping concentration of pillars. Therefore, a structure with different doping concentrations segmented within the pillar is being researched. Using Silvaco TCAD simulation, a SJ VVD (vertical variation doping profile) MOSFET with three different doping concentrations in the pillar was studied. Simulations were conducted for the width of the pillar and the doping concentration of N-epi, revealing that as the width of the pillar increases, the depletion region widens, leading to an increase in on-specific resistance (Ron,sp) and breakdown voltage (BV). Additionally, as the doping concentration of N-epi increases, the number of carriers increases, and the depletion region narrows, resulting in a decrease in Ron,sp and BV. The optimized SJ VVD MOSFET exhibits a very high figure of merit (BFOM) of 13,400 KW/cm², indicating excellent performance characteristics and suggesting its potential as a next-generation highperformance power device suitable for practical applications.

Nitrogen-doped graphene was synthesized by a hydrothermal method using graphene oxide (GO) as the raw material, urea as the reducing agent and nitrogen as the dopant. The morphology, structure, composition and electrochemical properties of the samples are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorptiondesorption analysis, electrical conductivity and electrochemical tests. The results show that urea can effectively reduce GO and achieve nitrogen doping under the hydrothermal conditions. By adjusting the mass ratio of raw materials to dopants, the graphene with different nitrogen doping contents can be obtained; the nitrogen content range is from 5.28~6.08% (atomic fraction percentage).When the ratio of dopant to urea is 1:30, the nitrogen doping content reaches a maximum of 6.08%.The supercapacitor performance test shows that the nitrogen content prepared by the ratio of 6.08% is the best at 0.1 A·g^-1. The specific capacitance is 95.2 F·g^-1.

The high cost of crystalline silicon solar cells has been considered as one of the major obstacles to their terrestrial applications. Spin on doping (SOD) is presented as a useful process for the manufacturing of low cost solar cells. Phosphorus (P509) was used as an n-type emitters of solar cells. N-type emitters were formed on p-type EFG ribbon Si wafers by using a SOD at different spin speed (1,000∼4,000 rpm), diffusion temperatures (800℃∼950℃), and diffusion time (5∼30 min) in N2+O2 atmosphere. With optimum condition, we were able to achieve cell efficiency of 14.1%.