Extended balance equations accounting for the conduction-valence interband impact ionization (II) process in semiconductor heterostructures are presented. The II effect and terahertz (THz) field influence on electron transport in InAs/AlSb heterostructures is studied. It is shown that the II process usually results in a decrease in electron velocity and temperature when compared to the case without the II process. Qualitative agreement is obtained between the calculated electron-hole generation rates and available experimental data. Comparison with published experimental data on THz-driven heterostructures is also made.

Multipacting is a phenomenon in which electrons grow sharply under certain conditions in a RF structure. It may lead to the breakdown or even damage to the equipment. Therefore, it is very important to calculate the Multipacting range in the RF equipment design. Since the phenomenon is too complicated to use the formula to fully predict it, numerical simulation is employed. There are many computer codes (such as Track3P, MultiPac, CST PS, etc.) used to simulate the phenomenon, but most of them are not commercial. In this paper, theories used in coaxial line for predicting multipacting are introduced; the CST PS is chosen to simulate the multipacting of coaxial coupler for BNCT DTL; finally, methods of suppressing multipacting are discussed.