Si/SiC heterostructural impact avalanche transit time (IMPATT) diode indicates of important applications in Terahertz (THz) power source, integrated circuit etc. In this paper, the (n)Si/(p)4H-SiC, (n)Si/(p)6H-SiC, (n)Si/(p)3C-SiC heterostructural double drift region IMPATT diodes operating at the atmospheric window frequency of 0.85 THz are designed by the drift-diffusion model while their static state, large signal and noise properties are numerically simulated. The performance parameters of the studied devices such as breakdown voltage, peak electric field strength, optimal negative conductance, output power, power conversion efficiency, admittance-frequency relation, quality factor, noise electric field, mean-square noise voltage per band-width and noise measure were calculated and compared. This method can guide for optimizing the Si/SiC heterostructural IMPATT device in the future.

SiC heteropolytype structures indicate important applications in high frequency, large power solid devices etc. In this paper, the impact avalanche transit time (IMPATT) and mixed tunneling avalanche transit time (MITATT) diodes with heteropolytype consisting of two semiconductors among the 3C-SiC, 4H-SiC and 6H-SiC are numerically simulated to investigate the static state and small signal characteristics at the atmospheric window frequency of 1.56 THz. The breakdown voltage, avalanche voltage, peak value of static electric field, the maximum generation rates of avalanche and tunneling, power conversion efficiency, admittance-frequency relation of the proposed SiC heteropolytype diodes are calculated, respectively. Comparing the obtained parameters of IMPATT diodes with those of MITATT devices, the results imply that tunneling shows little influence on the small signal performance of the heteropolytype IMPATT diodes included 3C-SiC material, which is different from those of the homopolytype counterparts.

Based on the composite dielectric polarization theory, dielectric permittivity, dissipation factor and loss angle tangent of hydrated paraffin versus temperature and power supply frequency were analyzed. The effect of different water contents in paraffin on its dielectric characteristics was also studied. The more the water content in hydrated paraffin, the greater the dielectric parameters, dissipation factor can reach 1.48 when the water contents was 15%. They can provide references for theoretical researches and industrial applications on removal of paraffin that condense on the interior walls of oil pipes in oil extraction by electric heating method.