-A grid-shadow effect is observed in grid-enhanced plasma source ion implantation, in which ions produced within the plasma region are extracted through a grid electrode and then accelerated to the inner surface of a cylindrical bore for implantation. By simulating the ion transportation behaviors from the grid electrode to the inner surface using a Monte Carlo model, we find that the grid-shadow effect results from grid blocking of the ion emission on the grid electrode, and it varies with the experimental parameters such as the gap distance between the grid electrode and the inner surface, the gas pressure, and the applied negative potential.

Using a two-dimensional ensemble Monte Carlo (EMC) method, the noise spectrum of a InGaAs-based nanoFET is studied in detail. Simulation results show that the noise spectrum consists of two maxima at frequencies of about 0.7 THz and 2 THz. The lower-frequency maximum is sensitive to the source-drain voltage, while that of the higher frequency one is not. These achievements are coincident with experimental results. Moreover, based on Dyakonv-Shur’s theory, the emergence of noise maxima is explained as the excitation of 2D plasma waves in the device.