Properties of Halide Perovskite Photodetectors with Little Rubidium Incorporation

This study investigates the effects of Rb doping on the Rb-formamidinium-methylammonium-PbI3 based perovskite photodetectors. Rb was incorporated in the perovskite films with different contents, and the corresponding photo-response properties were studied. Doping of few Rb (~2.5%) was found to greatly increase the grain size and the absorbance of the perovskite. However, when the Rb content was greater than 2.5%, clustering of the Rb-rich phases emerged, the band gap decreased, and additional absorption band edge was found. The excess Rb-rich phases were the main cause that degraded the performance of the photodetectors. By space charge limit current analyses, the Rb was found to passivate the defects in the perovskite, lowering the leakage current and reducing the trap densities of carriers. This fact was used to explain the increase in the detectivity. To clarify the effect of Rb, the photovoltaic properties were measured. Similarly, h perovskite with 2.5% Rb doping increased the short-circuit current, revealing the decline of the internal defects. The 2.5% Rb doped photodetector showed the best performance with responsivity of 0.28 AW−1 and ~50% quantum efficiency. Detectivity as high as 4.6 × 1011 Jones was obtained, owing to the improved crystallinity and reduced defects.

Transparent Bipolar Thin Film Transistors Based on Topological Insulator of Magneto-Resistive Effect

Thin film transistors using SiOC insulation film generated a very large IDS current with tunneling phenomena due to the occurrence of space charge limit current due to magnetic resistance effect. When SiOC gate insulation barrier transistor characteristics were investigated, transmission characteristics of bi-directional were observed, low current at levels ~10−7 A, but switching characteristics were superior to or greater than 10−10 A. SiOC Thin Film Insulation Characteristics are a good material for observing magnetic resistance effects, SiOC Transistors without channels clearly demonstrate the difference in spatial charges due to electromagnetic phenomena, and even in low-current insulation, nano-current flows at high speed. The current due to magnetic resistance is bi-directional and has an alternating current that flows in both directions at 0 V.

Mechanism of Carrier Transport in n-Type β-FeSi2/Intrinsic Si/p-Type Si Heterojunctions

Preparation of n-type β-FeSi2/intrinsic Si/p-type Si heterojunctions was accomplished by facing-target direct-current sputtering (FTDCS) and measuring their current-voltage characteristic curves at low temperatures ranging from 300 K down to 50 K. A mechanism of carrier transport in the fabricated heterojunctions was investigated based on thermionic emission theory. According to this theory, the ideality factor was calculated from the slope of the linear part of the forward lnJ-V plot. The ideality factor was 1.12 at 300 K and increased to 1.99 at 225 K. The estimated ideality factor implied that a recombination process was the predominant mechanism of carrier transport. When the temperatures decreased below 225 K, the ideality factor was estimated to be higher than two and parameter A was estimated to be constant. The obtained results implied that the mechanism of carrier transport was governed by a trap-assisted multi-step tunneling process. At high forward bias voltage, the predominant mechanism of carrier transport was changed into a space charge limit current process.