Area-restricted illumination of light onto a voltage-biased single-electron tunnel junction array is modeled by reduced resistance of junctions, and its effects on current-voltage characteristics, charge distributions and potential profiles are calculated by a Monte Carlo method. The results show that photocurrent nearly proportional to the applied voltage is generated above a threshold voltage determined by Coulomb blockade effect. The photocurrent increases with increasing irradiated area, which is ascribed to reduction in total resistance of the circuit. Under irradiation, a characteristic charge distribution is formed, i. e. , negative and positive charge bumps are formed in the nodes at the dark and bright boundaries. The charge bumps serve to screen the electric field formed by the bias voltage and create almost a flat potential in the irradiated area. Furthermore, time-response of the charge distribution to a pulse irradiation is also studied. For high dark resistance, the charge bumps are sustained for a long period working as a memory of light. These results suggest feasibility of single-electron photonic devices such as photodetectors and photomemories.

We propose a nonlocal impact ionization model applicable for the drain region where electric field increases exponentially. It is expressed as a function of an electric field and a characteristic length which is determined by a thickness of gate oxide and a source/drain junction depth. An analytical substrate current model for n-MOSFET is also derived from the new nonlocal impact ionization model. The model well explains the reason why the theoretical characteristic length differs from empirical expressions used in a pseudo two-dimensional model for MOSFET's. The nonlocal impact ionization model implemented in a device simulator demonstrates that the new model can predict substrate current correctly in the framework of drift-diffusion model.

Thin Si films grown on anodized porous silicon have been characterized using a high-energy ion scattering technique with related simulations of MeV ions in solids. It turned out that the simulations are necessary and very usuful for quantitative and nondestractive analysis of thin films with thicknesses less than 100 nm. In the case of the epitaxial Si films examined, it is often insufficient for the characterization of crystalline quality to measure only the channeling minimum yield, and therefore, it is emphasized that angular scans over the critical angle in the vicinity of a channeling direction must be performed for the analysis of possible imperfections in thin films. The possible imperfections observed in the epitaxial specimen are treated quantitatively.