Papers by Author: Il Ki Han

Abstract: This paper presents a simple and novel model for low-frequency noise generation in polycrystalline-Si resistors within the number fluctuation model. The grain boundary in polycrystalline-Si thin films is the major source of noise and is modeled as independent symmetric Schottky barriers in series, face-to-face. It has been found that trapping and detrapping of the carriers at the traps in the space charge region of the grain boundary via thermal activation modulate the barrier height and generate the low-frequency noise. The model successfully explains the experimental data and gives useful information about the defects in the space charge region of the grain boundary. As a result, the Hooge parameter is interpreted in terms of defect density, among other parameters.

Abstract: We report effects of the size and the energy state distribution on the electrical and optical properties in self-assembled InAs quantum dots. The results of characteristics measured using atomic force microscopy, photoluminescence and dark current are analyzed by way of a simulation assuming a Gaussian distribution in size and related energies. The samples investigated in this study are InAs/GaAs quantum dot infrared photodetector structures with an AlGaAs blocking layer grown by molecular beam epitaxy at different growth modes.

Abstract: Silicon nanocrystals in a range from 2 nm to 5 nm were prepared from Zintl salt, soldium silicide (NaSi) by sonochemical method. This synthesis permits that the reaction be completed in only a few hours and the easy alkyl-modification of nanocrystals surface at room temperature and ambient pressure. The average size of nanocrystals measured by the dynamic light scattering analysis was 2.7 nm. The high-resolution transmission electron micrograph confirmed the material identity of nanocrystals as crystalline silicon. FT-IR spectra are consistent with the surface states of nanocrystals that are chlorine-or butyl-capped. The emission peak center moved to a longer wavelength (up to 430 nm) with the reaction time, under a 325 nm excitation.