Zhiguo Meng

Vanadium pentoxide modified polycrystalline silicon anode for active-matrix organic light-emitting diodes

Recently, polycrystalline silicon (p-Si) has been demonstrated to be an efficient anode for organic light-emitting diode (OLED) [X. L. Zhu, J. X. Sun, H. J. Peng, Z. G. Meng, M. Wong, and H. S. Kwok, Appl. Phys. Lett. 87, 083504 (2005)]. In this letter, we show that, by depositing an ultrathin vanadium pentoxide (V2O5) layer on the p-Si anode, the performance of the OLED can be greatly improved. Detailed x-ray photoelectron spectroscopy study shows that strong band bending occurs at the p-Si∕V2O5 interface, leading to much stronger hole injection. This modified p-Si anode can be integrated with the active p-Si layer of thin-film transistors in active-matrix OLED displays.

Three-terminal bistable twisted nematic liquid crystal displays

A three-terminal bistable twisted nematic liquid crystal display has been demonstrated. This display makes use of a combination of strong in-plane electric fields and vertical electric field for switching between the φ and the φ+π twist states. The lifetimes of the two bistable twist states are infinite, which is a significant improvement over conventional bistable twisted nematic displays.

The effects of high temperature annealing on metal-induced laterally crystallized polycrystalline silicon

Metal-induced laterally crystallized (MILC) polycrystalline silicon (poly-Si) with and without a post-crystallization high temperature anneal have been studied and compared. It was revealed using transmission electron microscopy (TEM) that the anneal resulted in significant improvement in the material quality. Consequently, the electrical properties of the annealed MILC poly-Si resistors were greatly enhanced, showing conduction behavior approaching that of single-crystal Si. Thin-film transistors realized on high-temperature annealed MILC poly-Si exhibited excellent device characteristics, thus making them potentially applicable to three-dimensional (3-D) device integration. Based on the TEM observations and a detailed consideration of the mechanism of grain growth during MILC, the effects of the anneal can be explained in terms of the evolution of the unique MILC grain structure during the high temperature treatment.

Active-matrix organic light-emitting diode displays realized using metal-induced unilaterally crystallized polycrystalline silicon thin-film transistors

Requirement on thin-film transistors, particularly in terms of current-drive and parameter uniformity, for active-matrix organic light-emitting diode displays, was analyzed. Metal-induced unilaterally crystallized polycrystalline silicon thin-film transistor technology was shown to satisfy such and other demands. Though pixel designs involving more transistors were certainly advantageous, appropriate biasing scheme allowed a simpler and larger aperture-ratio two-transistor design. As a demonstration, active matrices were fabricated and integrated with organic light-emitting diodes to make monochrome video display panels, each consisting of 120 rows and 160 columns.

Bridged-Grain Solid-Phase-Crystallized Polycrystalline-Silicon Thin-Film Transistors

Novel bridged-grain (BG) technique is applied in the fabrication of low-temperature solid-phase-crystallized polycrystalline-silicon thin-film transistors. As a result of improved current flow and reduction of high drain electric field, the subthreshold slope, threshold voltage, maximum field-effect mobility, leakage current, and on-off ratio are greatly improved. Mechanisms of BG conduction are studied in detail.

Polycrystalline silicon films and thin-film transistors using solution-based metal-induced crystallization

Polycrystalline silicon (poly-Si) films consisting of dish-like and wadding-like domains were obtained with solution-based metal-induced crystallization (SMIC) of amorphous silicon. The Hall mobility of poly-Si was much higher in dish-like domains than in wadding-like domains. Thin-film transistors (TFTs) have been prepared using those two kinds of poly-Si films as the active layer, followed by the phosphosilicate glass (PSG) nickel gettering. The field effect mobility of dish-like domain poly-Si TFTs and wadding-like poly-Si TFTs were 70~80 cm2/Vmiddots and 40~50 cm2/Vmiddots, respectively. With a multi-gate structure, the leakage current of poly-Si TFTs was reduced by 1 to 2 orders of magnitude. In addition, the gate-induced drain leakage current (GIDL) and uniformity of the drain current distribution were also improved. P-type TFTs fabricated using SMIC exhibited excellent reliability

Polysilicon Thin Film-Transistors With Uniform and Reliable Performance Using Solution-Based Metal-Induced Crystallization

The authors studied electrical characteristics of p-channel polycrystalline silicon thin-film transistors (TFT) fabricated by solution-based metal-induced crystallization (SMIC). In particular, the effect of annealing conditions was systematically investigated. The current-voltage characteristics show that the performance of TFTs was dominated by the SMIC process rather than the annealing temperature up to 630 degC. All the devices exhibited good uniformity after annealing. The effects of gate stress and self-heating stress were also studied. The device performance was not affected by both stresses for all devices, p-channel SMIC poly-Si TFT has high performance, good uniformity, and satisfactory reliability with a process temperature < 600 degC

Metal-induced laterally crystallized polycrystalline silicon for integrated sensor applications

A novel metal-induced lateral crystallization (MILC) technique, involving a low temperature crystallization step followed by a high temperature recrystallization step, has been applied to the formation of polycrystalline silicon (poly-Si) with enhanced material characteristics. A range of devices, including piezo-resistors, thermistors, resistors and thin-film transistors, has been fabricated both on MILC and regular low-pressure chemical vapor deposited (LPCVD) poly-Si. Compared to the latter, MILC poly-Si leads to much improved device performance. The piezo-resistive gauge factor of MILC poly-Si is at least double that of LPCVD poly-Si, with a maximum value of 60 measured, higher mobility, steeper subthreshold slope, lower threshold voltage, and higher on-off current ratio have been obtained for thin-film transistors realized on MILC poly-Si that those realized on LPCVD poly-Si. A variety of sensing and electronic devices based on MILC poly-Si can be simultaneously realized, thus making MILC an enabling technology for integrated silicon sensor applications.

Bridged-Grain Polycrystalline Silicon Thin-Film Transistors

We introduce a new structure for low-temperature polycrystalline silicon thin-film transistors (TFTs). This bridged-grain structure can reduce the threshold voltage and the subthreshold swing, increase the on-off ratio, and suppress leakage current and kink effect of TFTs significantly. This technique can be applied to all polycrystalline silicon TFTs, including those made by solid-phase crystallization, metal-induced crystallization, metal-induced lateral crystallization, and excimer laser annealing.

Efficient organic light-emitting diodes using polycrystalline silicon thin films as semitransparent anode

Polycrystalline silicon (p-Si) is a good material for the construction of thin-film transistors (TFT). It is used for fabricating active-matrix organic light-emitting diode (AMOLED) displays. In this letter, we propose and demonstrate the application of boron-doped p-Si as a semi-transparent anode in making different color OLEDs. Without removing the ultrathin native oxide on the p-Si surface and employing p-doped hole transport layer to enhance holes injection, these OLEDs show comparable or even better performance to conventional OLEDs which use ITO as anodes. The present technique has the advantage of less masking steps in making AMOLED.