Exploring the potential of the fabrication of large-size mirror facet for semiconductor laser bar utilizing mechanical cleavage

While mechanical cleavage technology is an ideal alternative approach to fabricate large-size mirror facets for high-power laser bar, there has been little scientific understanding of mechanical cleavage mechanisms. To fill this gap, cleavage experiments were designed according to the Taguchi method for analyzing the main effects of three parameters. Surface and subsurface cracks and cleavage plane morphology are analyzed as well. The results show that scribing load has significant impact on the scratch morphology as compared with other parameters, and quadratic polynomial models are formulated to predict kerf width and maximum damage width values. For scribing along the [0−1−1] direction on the (100) GaAs wafer, the subsurface cracks are TLC and LC which propagate along [0-11] direction and MC which propagates along [100] direction. The achieved optimal combination of parameters are scribing load of 10 g, scribing speed of 20 mm/s and scribing length of 0.6 mm. The undamaged length of cleaved planes can reach 11.77 mm. Our results demonstrate that mechanical cleavage is a powerful technique which could guide actual production and manufacturing field of high-power GaAs-based laser bars.     

Interface engineering of bi-layer semiconductor SrCoSnO3-δ-CeO2-δ heterojunction electrolyte for boosting the electrochemical performance of low-temperature ceramic fuel cell

A comparative study is performed to investigate the electrochemical performance of the low-temperature ceramic fuel cells (CFCs) utilizing two different novel electrolytes. First, a perovskite semiconductor SrCo_0.3Sn_0.7O_3-δ was used as an electrolyte in CFCs due to its modest ionic conductivity (0.1 S/cm) and demonstrated an acceptable power density of 360 mW/cm² at 520 °C. The performance of the cell was primarily limited due to the moderate ionic transport in the electrolyte. In order to improve the ionic conductivity, a new strategy of using a novel bi-layer electrolyte concept consist of SrCo_0.3Sn_0.7O_3-δ and CeO_2-δ in CFCs. These bi-layers of two electrolytes have successfully established heterojunction which considerably improved the ionic conductivity (0.2 S/cm) and enhance the open-circuit voltage of the cell from 0.98 V to 1.001 V. Moreover, the CFCs utilizing bi-layer electrolyte have produced a remarkable power density of 672 mW/cm² at 520 °C. This enhancement of ionic conduction, power density and blockage of electron conduction in the bi-layer electrolyte was studied via band alignment mechanism based on proposed p-n heterojunction. Our work presents a promising methodology for developing advanced low-temperature CFC electrolytes.     

半导体激光器的输出功率控制及输出光信号调制

运用自动控制理论，结合实际的控制系统，介绍了半导体激光器输出功率的稳定控制以及如何在要求输出功率稳定的条件下，对输出光信号进行调制，从而为实际应用半导体激光器中面临的功率稳定性问题，提供了一种行之有效的解决办法。     

Direct parameter-extraction method for MOSFET noise model from microwave noise figure measurement

A new method for the determination of the four noise parameters of the metal oxide semiconductor field effect transistors (MOSFETs) based on the noise figure measurement system without microwave tuner is presented. The noise parameters are determined based on a set of analytical expressions of noise parameters by fitting the measured noise figure of the active device. These expressions are derived from an accurate small signal and noise equivalent circuit model, which takes into account the substrate parasitics, pad capacitances, and series inductances. On-wafer experimental verification is presented and a comparison with tuner based method is given. Good agreement is obtained between simulated and measured results for 0.5 × 5 × 16 μm, 0.35 × 5 × 16 μm and 0.18 × 5 × 16 μm (gate length × number of gate fingers × unit gate width) MOSFETs.     

Investigation of MOSFET operation in bipolar mode

The work is concerned with the properties of conventional MOSFET in bipolar mode of operation. It is shown that the base current can provide useful information about interface trap density at the Si–SiO₂ interface. The new device characteristics are found promising for use in low-voltage low-power logic circuits.     

半导体晶圆的污染杂质及清洗技术

介绍了半导体圆片存在的各种污染杂质的类型和去除方法,并概要总结了半导体圆片的清洗技术,对半导体圆片的湿法和干法清洗特点和去除效果进行了比较分析。     

Semiconducting ground-state of three polymorphs of Mg2NiH4 from first-principles calculations

Magnesium nickel hydrides (Mg₂NiH₄) are the prospective candidates for hydrogen storage and switchable mirror. The hydrides exist in two typical crystallographic forms, the low temperature (LT) phase in monoclinic structure, and the high temperature (HT) phase in cubic structure. LT has two modifications–untwinned (LT1) and microtwinned (LT2) structures. The electronic structures of the three polymorphs of Mg₂NiH₄ are investigated using ab initio calculations based on density functional theory. The calculated band gaps of LT1 and HT are in reasonable agreement with experimental observations and other theoretical predications, while the calculated band gap of LT2 is slightly lower than those of LT1 and HT. Electronic-structure analysis shows that strong interactions exist between Ni and H, whereas the interactions between Mg and H are negligible. The strong ionic character between Mg and NiH₄ complex can be viewed as the origin of the semiconducting ground-state.     

Photolithographic Route to the Fabrication of Micro/Nanowires of III–V Semiconductors

Nano/microwires of semiconducting materials (e.g., GaAs and InP) with triangular cross‐sections can be fabricated by “top–down” approaches that combine lithography of high‐quality bulk wafers (using either traditional photolithography or phase‐shift optical lithography) with anisotropic chemical etching. This method gives good control over the lateral dimensions, lengths, and morphologies of free‐standing wires. The behaviors of many different resist layers and etching chemistries are presented. It is shown how wire arrays with highly ordered alignments can be transfer printed onto plastic substrates. This “top–down” approach provides a simple, effective, and versatile way of generating high‐quality single‐crystalline wires of various compound semiconductors. The resultant wires and wire arrays have potential applications in electronics, optics, optoelectronics, and sensing.     

外腔半导体激光器的场功率谱和线宽

本文采用低频近似的方法,用半经典理论,给出了外腔半导体激光器的场功率谱和线宽公式,理论分析与实验结果是吻合的。     

Amorphous Silicon 16—bit Array Photodetector^①

An amorphous silicon 16-bit array photodetector with the a-SiC/a -Si heterojunction diode is presented. The fabrication processes of the device were studied systematically. By the optimum of the diode structure and the preparation procedures, the diode with Id< 10 -12 A/mm2 and photocurrent Ip^0.35 A/W has been obtained at the wavelength of 632 nm.