Shengdong Zhang

Bio: Shengdong Zhang is an academic researcher from Peking University. The author has contributed to research in topics: Thin-film transistor & Threshold voltage. The author has an hindex of 30, co-authored 479 publications receiving 3806 citations. Previous affiliations of Shengdong Zhang include China-Japan Friendship Hospital & Hong Kong University of Science and Technology.

A novel ultrathin elevated channel low-temperature poly-Si TFT

Abstract: A novel ultrathin elevated channel thin-film transistor (UT-ECTFT) made using low-temperature poly-Si is proposed. The structure has an ultrathin channel region (300 /spl Aring/) and a thick drain/source region. The thin channel is connected to the heavily doped drain/source through a lightly doped overlapped region. The lightly doped overlapped region provides an effective way to spread out the electric field at the drain, thereby reducing significantly the lateral electric field there at high drain bias. Thus, the UT-ECTFT exhibits excellent current saturation characteristics even at high bias (V/sub ds/=30 V, V/sub gs/=20 V). Moreover, the UT-ECTFT has more than two times increase in on-state current and 3.5 times reduction in off-state current compared to conventional thick channel TFT's.

Solution‐Processed MoS2/Organolead Trihalide Perovskite Photodetectors

Abstract: Integration of organic/inorganic hybrid perovskites with metallic or semiconducting phases of 2D MoS2 nanosheets via solution processing is demonstrated. The results show that the collection of charge carriers is strongly dependent on the electronic properties of the 2D MoS2 with metallic MoS2 showing high responsivity and the semiconducting phase exhibiting high on/off ratios.

Efficient quantum dot light-emitting diodes with a Zn0.85Mg0.15O interfacial modification layer

Abstract: Efficient inverted quantum-dot (QD) light-emitting diodes (LEDs) are demonstrated by using 15% Mg doped ZnO (Zn0.85Mg0.15O) as an interfacial modification layer. By doping Mg into ZnO, the conduction band level, the density of oxygen vacancies and the conductivity of the ZnO can be tuned. To suppress excess electron injection, a 13 nm Zn0.85Mg0.15O interlayer with a relatively higher conduction band edge and lower conductivity is inserted between the ZnO electron transport layer and QD light-emitting layer, which improves the balance of charge injection and blocks the non-radiative pathway. Moreover, according to the electrical and optical studies of devices and materials, quenching sites at the ZnO surface are effectively reduced by Mg-doping. Therefore exciton quenching induced by ZnO nanoparticles is largely suppressed by capping ZnO with Zn0.85Mg0.15O. Consequently, the red QLEDs with a Zn0.85Mg0.15O interfacial modification layer exhibit superior performance with a maximum current efficiency of 18.69 cd A−1 and a peak external quantum efficiency of 13.57%, which are about 1.72- and 1.74-fold higher than 10.88 cd A−1 and 7.81% of the devices without Zn0.85Mg0.15O. Similar improvements are also achieved in green QLEDs. Our results indicate that Zn0.85Mg0.15O can serve as an effective interfacial modification layer for suppressing exciton quenching and improving the charge balance of the devices.

Investigation on Thermally Induced Efficiency Roll-Off: Toward Efficient and Ultrabright Quantum-Dot Light-Emitting Diodes

Abstract: Quantum-dot light-emitting diodes (QLEDs) with high brightness have potential application in lighting and display. The high brightness is realized at high current density (J). However, at high J, the efficiency drops significantly, thereby limiting the achievable brightness. This notorious phenomenon has been known as efficiency roll-off, which is likely caused by the Auger- and/or thermal-induced emission quenching. In this work, we show that the Joule heat generated during device operation significantly affects the roll-off characteristics of QLEDs. To realize ultrabright and efficient QLEDs, the thermal stability of QDs is improved by replacing the conventional oleic acid ligands with 1-dodecanethiol. By further using a substrate with high thermal conductivity, the Joule heat generated at high J is effectively dissipated. Because of the effective thermal management, thermal-induced emission quenching is significantly suppressed, and consequently, the QLEDs exhibit a high external quantum efficiency (EQE) of 16.6%, which is virtually droop-free over a wide range of brightness (e.g., EQE = 16.1% @ 105 cd/m2 and 140 mA/cm2). Moreover, due to the reduced efficiency roll-off and enhanced heat dissipation, the demonstrated QLEDs can be operated at a very high J up to 3885 mA/cm2, thus enabling the devices to exhibit a record-high brightness of 1.6 × 106 cd/m2 and a lumen density of 500 lm/cm2. Our work demonstrates the significance of thermal management for the development of droop-free and ultrabright QLED devices for a wide variety of applications including lighting, transparent display, projection display, outdoor digital signage, and phototherapy.

Numerical modeling of linear doping profiles for high-voltage thin-film SOI devices

Abstract: A numerical model for obtaining linear doping profiles in the drift region of high-voltage thin-film SOI devices is proposed and experimentally verified. Breakdown voltage in excess of 612 V on LDMOS transistors with 0.15-/spl mu/m SOI layer, 2-/spl mu/m buried oxide, and 50-/spl mu/m drift region is designed and demonstrated using this model. Theoretical and experimental dependence of the breakdown voltage on the drift region length are compared. Good agreement between the simulation and experimental results are obtained. Dependence of the breakdown voltage on the doping density and doping concentration slope in the linearly doped drift region is also investigated experimentally. Results indicate that an optimum concentration slope is needed in order to optimize the breakdown voltage in the thin-film SOI devices with a linear doping drift region. Finally, a 600-V CMOS compatible thin-film SOI LDMOS process is also described.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Semiconductor device, and manufacturing method thereof

Abstract: An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Issues and opportunities facing aqueous zinc-ion batteries

Abstract: Zinc-ion batteries built on water-based electrolytes featuring compelling price-points, competitive performance, and enhanced safety represent advanced energy storage chemistry as a promising alternative to current lithium-ion battery systems. Attempts to develop rechargeable aqueous zinc-ion batteries (ZIBs) can be traced to as early as the 1980s; however, since 2015, the research activity in this field has surged throughout the world. Despite the achievements made in exploring electrode materials so far, significant challenges remain at the material level and even on the whole aqueous ZIBs system, leading to the failure of ZIBs to meet commercial requirements. This review aims to discuss how to pave the way for developing aqueous ZIBs. The current research efforts related to aqueous ZIBs electrode materials and electrolytes are summarized, including an analysis of the problems encountered in both cathode/anode materials and electrolyte optimization. Some concerns and feasible solutions for achieving practical aqueous ZIBs are discussed in detail. We would like to point out that merely improving the electrode materials is not enough; synergistic optimization strategies toward the whole battery system are also deeply needed. Finally, some perspectives are provided on the subsequent optimization design for further research efforts in the aqueous ZIB field.