Reliability of Active-Matrix Organic Light-Emitting-Diode Arrays With Amorphous Silicon Thin-Film Transistor Backplanes on Clear Plastic

We have fabricated active-matrix organic light emitting diode (AMOLED) test arrays on an optically clear high-temperature flexible plastic substrate at process temperatures as high as 285 degC using amorphous silicon thin-film transistors (a-Si TFTs). The substrate transparency allows for the operation of AMOLED pixels as bottom-emission devices, and the improved stability of the a-Si TFTs processed at higher temperatures significantly improves the reliability of the light emission over time.     

Amorphous Silicon Thin-Film Transistor Backplanes Deposited at 200 °C on Clear Plastic for Lamination to Electrophoretic Displays

The transition of thin-film transistor (TFT) backplanes from rigid plate glass to flexible substrates requires the development of a generic TFT backplane technology on a clear plastic substrate. To be sufficiently stable under bias stress, amorphous-silicon (a-Si:H) TFTs must be deposited at elevated temperatures, therefore the substrate must withstand high temperatures. We fabricated a-Si:H TFT backplanes on a clear plastic substrate at 200degC. The measured stability of the TFTs under gate bias stress was superior to TFTs fabricated at 150degC. The substrate was dimensionally stable within the measurement resolution of 1, allowing for well-aligned 8 times 8 and 32 times 32 arrays of pixels. The operation of the backplane is demonstrated with an electrophoretic display. This result is a step toward the drop-in replacement of glass substrates by plastic foil.     

Solid-phase Crystallization of Hydrogenated Amorphous Silicon on Glass Substrates

Amorphous silicon films prepared by PECVD on glass substrate have been crystallized by conventional furnace annealing and rapid thermal annealing（RTA）, respectively. From the Raman spectra, X- ray diffraction and scanning electron microscope, it is found that the grain size is crystallized at 850 ℃ in both techniques. The thin film made by RTA is smooth and of perfect structure, the thin film annealed by FA has a highly structural disorder. An average grain size of about 30 nm is obtained by both techniques.     

Comparison of Pentacene and Amorphous Silicon AMOLED Display Driver Circuits

Organic light-emitting diode (OLED) displays offer distinct advantages over liquid crystal displays for portable electronics applications, including light weight, high brightness, low power consumption, wide viewing angle, and low processing costs. They also are attractive candidates for highly flexible substrates. In active-matrix OLED (AMOLED) displays, a small transistor circuit is used to drive each OLED device. This paper compares the simulated performance of two state-of-the-art AMOLED drivers with a proposed 5 thin-film-transistor (TFT) voltage programmed driver circuit which combines the advantages of the first two configurations. A competitive evaluation is also done between amorphous silicon (alpha-Si) and organic TFTs (OTFTs,) using comparable empirical device models for alpha-Si) and pentacene OTFTs. The 5-TFT circuit is found to match the speed of the 2-TFT while achieving a stability closer to the 4-TFT circuits and demonstrating a better speed-stability tradeoff.     

Low-Temperature Epitaxy of Compressively Strained Silicon Directly on Silicon Substrates

We report epitaxial growth of compressively strained silicon directly on (100) silicon substrates by plasma-enhanced chemical vapor deposition. The silicon epitaxy was performed in a silane and hydrogen gas mixture at temperatures as low as 150°C. We investigate the effect of hydrogen dilution during the silicon epitaxy on the strain level by high-resolution x-ray diffraction. Additionally, triple-axis x-ray reciprocal-space mapping of the samples indicates that (i) the epitaxial layers are fully strained and (ii) the strain is graded. Secondary-ion mass spectrometry depth profiling reveals the correlation between the strain gradient and the hydrogen concentration profile within the epitaxial layers. Furthermore, heavily phosphorus-doped layers with an electrically active doping concentration of ~2 × 10²⁰ cm⁻³ were obtained at such low growth temperatures.     

Complementary Logic Gates and Ring Oscillators on Plastic Substrates by Use of Printed Ribbons of Single-Crystalline Silicon

CMOS inverters and three-stage ring oscillators were formed on flexible plastic substrates by transfer printing of p-type and n-type single crystalline ribbons of silicon. The gain and the sum of high and low noise margins of the inverters were as high as ~150 and 4.5 V at supply voltages of 5 V, respectively. The frequencies of the ring oscillators reached 2.6 MHz at supply voltages of 10 V. These results, as obtained with devices that have relatively large critical dimensions (i.e., channel lengths in the several micrometer range), taken together with good mechanical bendability, suggest promise for the use of this type of technology for flexible electronic systems.     

Si衬底氮化物LED器件的研究进展

通过对比分析目前氮化物LED的三种主要衬底即蓝宝石、SiC与Si的技术特点,指出了发展Si衬底LED的重要意义。详细介绍了目前国内外Si衬底LED的研究现状,解析了在Si衬底上制备LED的多种新型技术,主要包括以提高薄膜沉积质量为目的的缓冲层技术、激光脱离技术、图案掩模技术、阳极氧化铝技术,以及以提高光提取率为宗旨的镜面结构技术和量子阱/量子点技术。这些新型技术与传统的MOCVD,HVPE,MBE等制备技术相结合,在很大程度上克服了Si衬底的不足,使Si衬底上氮化物LED展现出广阔的发展前景。     

非晶硅液晶光阀投影系统

首次介绍一种以非晶硅（ａ－Ｓｉ）为光导层的ＬＣＬＶ投影系统，该系统具有响应速度快、写入光谱范围宽及工艺简单等优点。分析了ＬＣＬＶ驱动信号的电压幅值、频率、占空比以及屏幕照度等诸多因素对投影系统对比度特性的影响。该投影系统屏幕尺寸为１．５ｍ×１．２ｍ，最大照度为１９０ｌｘ，分辨率优于２０ｌｐ／ｍｍ，响应时间小于１ｍｓ。可完成实时动态图像投影。     

Self-Stabilization in Amorphous Silicon Circuits

Thin-film transistors (TFTs) based on disordered semiconductors such as amorphous hydrogenated silicon (a-Si:H) experience a threshold voltage (VT) shift with time in the presence of a gate bias. The VT shift needs to be compensated for circuit applications. We study an interesting property of self-compensation in fundamental analog TFT circuits with one a part of the circuit compensating for the effects of VT shift in the other and vice versa.      

High-Rate Deposition of Amorphous Silicon

A method for rapid deposition of amorphous silicon (a-Si) films in a low-frequency (55 kHz) glow discharge plasma is suggested. The structure and electrophysical properties of the films were investigated. It is shown that the use of the low-frequency discharge makes it possible to independently control the stability and concentration of recombination centers in a-Si. This fact, along with the possibility of fabricating heterostructures with a low density of surface states, makes this method promising for mass production of a-Si-based electron devices.     

Sensing Amorphous/Crystalline Silicon Surface Passivation by Attenuated Total Reflection Infrared Spectroscopy of Amorphous Silicon on Glass

Semiconductors - Attenuated total reflection Fourier transform infrared (ATR FTIR) spectroscopy and effective lifetime measurements have been used to characterize amorphous/crystalline silicon...     

硅基键合激光器的研究进展

硅基的光电子集成以及光集成将满足未来信息传输处理的要求。目前制作硅基激光器的方法主要分为两类,异质结外延生长和异质材料键合。键事方法克服了异质结外 可避免的晶格失配和材料热膨胀系数非共容性的缺点,它可以将具有直接带隙结构的半导体材料键合到硅片上,从而制作出硅基键合激光器件。特别是年来来发展起来的低落曙直接合技术,使发光器件与微电子器件的硅基混合光电集成成为可能。     

Micromachined Loop Antennas on Low Resistivity Silicon Substrates

The integration of K-band (20-40 GHz) full wavelength square wire- and slot-loop antennas on low resistivity (11-70 Omegacm) silicon substrates is addressed. By the use of polymer or silicon oxide/nitride membranes to support the slot or wire loop over micromachined trenches the efficiency of the antennas is enhanced while the majority of the bulk silicon within the aperture of the antenna is preserved to enable the integration of active devices. A 3.6times3.6 mm² large slot loop antenna chip with 200 mum micromachined trench width yields 1.5 dBi gain at 29.5 GHz, while 1.0 dBi gain is obtained at 24 GHz for a wire loop antenna on a 4.5times4.5 mm² large chip with 360 mum wide trenches     

Resonant-Cavity-Enhanced Single-Photon Avalanche Diodes on Reflecting Silicon Substrates

In this letter, we report the first resonant-cavity-enhanced single-photon avalanche diode (RCE SPAD) fabricated on a reflecting silicon-on-insulator (SOI) substrate. The substrate incorporates a two-period distributed Bragg reflector fabricated using a commercially available double-SOI process. The RCE SPAD detectors have peak photon detection efficiencies ranging from 42% at 780 nm to 34% at 850 nm and time resolution of 35-ps full-width at half-maximum. Typical dark count rates of 450, 3500, and 100 000 c/s were measured at room temperature with RCE SPADs having, respectively 8-, 20-, and 50-mum diameter.     

Stability of Amorphous Silicon Solar Cells

The present situation on the stability of amorphous silicon solar cells is discussed. Impurity diffusion is not expected to be a problem in normal cell operation. Interface contamination degrades Schottky barrier or MIS cells that are exposed to water vapor, but has no influence on p-i-n or n-i-p cells. Optically induced changes in the amorphous silicon have an influence, depending on cell structure and preparation conditions. Preliminary results on ? 5% efficiency n-i-p cells suggest that the efficiency will degrade by only 20% in 20 years of sunlight.     

Realization of Flexible Plasma Display Panels on PET Substrates

DC plasma display panels are fabricated on flexible polyethylene terephtalate (PET) substrates. Each pixel consists of laterally placed anode and cathode electrodes. All electrical elements are formed on a single PET substrate, whereas a second substrate is needed to encapsulate the panel. Silver is used as the metal for each electrode and standard photolithography is used to form each cell. A 150-/spl mu/m-thick layer of a UV-curable polymeric adhesive was used to form barrier ribs to both electrically isolate neighboring cells and to encapsulate the plasma. Conversion of vacuum UV into visible light is possible by blast-embedding of proper phosphor grains into the top substrate. The current-voltage and turn-on voltage versus pressure characteristics are examined. Effect of curvature on turn-on voltage is addressed.     

Stability of an Amorphous Silicon Oscillator

An RC oscillator using amorphous silicon thin film transistors was developed. The oscillation frequency and its dependence on resistance and bias voltage were studied. The frequency was controlled by adjusting the feedback resistance of the oscillator. The highest measured frequency of the oscillator was around 140 kHz, which is acceptable for low‐end radio frequency identification (RFID). Since a low‐end RFID circuit needs low cost and a simple process, an amorphous silicon oscillator is suitable.     

Innovative Amorphous Silicon Balanced Ultraviolet Photodiode

An innovative balanced photodiode structure made in amorphous silicon/amorphous silicon carbide, suitable for detecting small current variations on a large background signal, is presented and characterized. The structure is a three-terminal device, constituted by two series-connected n-i-p photosensors, where the output signal is the difference between the currents flowing through the two diodes. The layer thickness and optical properties of the thin-film materials and the geometry of the structure have been optimized for the detection of ultraviolet radiation. Common mode rejection ratio (CMRR) values ranging between 30 dB at 254 nm and 42 dB at 365 nm have been measured, independent on the bias voltage. The decrease of the CMRR at lower wavelengths has been ascribed to differences in the surfaces of the two diodes exposed to the light.      

高掺杂氢化非晶硅薄膜

采用低浓度硅烷,低生长速率,在PECVD系统中制得高掺杂氢化非晶硅(N~+α-Si:H)薄膜,其电导率高达5～36Ω~(-1)cm~(-1)。应用该技术制成了新型二维电子气Si/N~+α-Si∶H异质结双极型晶体管,在硅微波功率异质结双极型晶体管研制上取得重大突破。     

平板显示器用塑料基片

介绍了具有多层涂膜的塑料基片,它们对于潮气和氧具有足够的不可渗透性,可用于对潮气灵敏的显示器,譬如LCD,小分子有机半导体发光二极管显示器和聚合物半导体发光二极管显示器.