少长针半导体消雷器至今没有正确的理论指导──对《半导体消雷针闪络后的限流作用》一文的理论基础的商榷

本文指出,《半导体消雷针闪络后的限流作用》一文的理论基础是不正确的,无条件地把Wagner理论和公式套用到整个雷电放电过程,特别是先导放电（或连续放电）过程是没有根据的,因而,该文所作的所有计算和推论都是不可信的。     

半导体GaN功率开关器件灵敏度测试技术

测试半导体GaN功率开关器件灵敏度对掌握器件性能具有重要意义,提出一种新的半导体GaN功率开关器件灵敏度测试技术。通过分析半导体GaN功率开关器件的导通电阻与击穿电压关系、空穴电流与栅极电流关系掌握功率开关器件击穿机理,在此基础上,测试半导体GaN功率开关器件灵敏度;根据灵敏度测试原理与微频通道衰减值周期检查原理,测量功率开关器件微频信号功率和微频通道衰减值,汇总微频通道衰减值和最后一次开关灵敏时的衰减值,得到半导体GaN功率开关器件灵敏度。实验结果表明：所提测试技术测量半导体GaN功率开关器件灵敏度过程中,平均测试误差为0.03 dB,仅平均花费9.42ms,是一种高效、可靠的半导体GaN功率开关器件灵敏度测试技术。     

Modification of X-ray Generator by Energy Reusing

X-ray is an important tool for charactering and analyzing materials. However, current X-ray generation is cost with low efficiency. For X-ray tube, which is mostly used in laboratories, only has an energy usage of 1% with all other energy dissipated into tremendous heats, and it needs continuous cool water flows to cool down the cathode. It generates X-ray by the bremsstrahlung of high energy electrons bombarding on the cathode target, the bremsstrahlung would contain X-ray with sufficiently high energy of the electrons. But most part of the electron energy becomes heats. In order to generate X-ray more cheaply with higher efficiency, methods about reusing the released heats during the working of the X-ray tube are brought up. Mimicking the photovoltaic effect, nonequilibrium carriers could also be injected via thermion emission when heating a metal, such injection is same to that of photonic injection which produces electromotive in a photovoltaic cell. In a photovoltaic cell the electron-hole pair generated by incident photons are nonequilibrium carriers that causes electromotive, while the thermion emission creates such electron-hole pairs via thermal excitation. Connecting metals suitable for thermion emission from the cathode into the p-n junction so that thermions as nonequilibrium carriers can be well injected into the p-n junction when the metals are heated by the cathode, with Thomson effect which enhances such injection, a thermal voltaic cell can be constructed and it can produce electricity only by heating the metals outside. Applying such thermal voltaic cell into current X-ray tube, it would produce electricity while absorbing the tremendous heats emerges when X-ray tube is working. Water flows are still used to control the temperature, but letting them boiling to keep the cathode at a temperature best for thermal voltaic cell, and the vapor may be used to drive a mini thermal power plant. In this way, the energy usage could be modified to a higher proportion. Stepwise up-conversion is possible to generate X-ray more cheaply but there are no suitable materials so far.     

GaAs半导体脉冲激光器的激励源

本文阐述了GaAs半导体脉冲激光器的电气特性及对激励源的要求。给出了较成熟的GaAs半导体脉冲激光器的激励源,并介绍了该激励源的工作原理。     

Polarization effects in nitride semiconductors and device structures

Wide bandgap nitride semiconductors have recently attracted a great level of attention owing to their direct bandgaps in the visible to ultraviolet regions of the spectrum as emitters and detectors. Moreover, this material system with its favorable hetero-junctions and transport properties began to produce very respectable power levels in microwave amplifiers. If and when the breakdown fields achieved experimentally approach the predicted values, this material system would also be very attractive for power switching devices. In addition to the premature breakdown, high concentration of defects, and inhomogeneities, a number of scientific challenges remain including a clear experimental investigation of polarization effects. In this paper, following a succinct review of the progress that has been made, spontaneous and piezoelectric polarization effects and their impact on sample device-like hetero-structures will be treated. Received: 5 April 1999 / Reviewed and accepted: 19 April 1999     

BaTiO_3、SrTiO_3陶瓷半导化机理的研究

探讨了烧结温度、冷却条件及 Nb_2O_5添加量对 BaTiO_3、SrTiO_3陶瓷半导化的影响。实验结果表明:在添加0.1～0.7mol%的 Nb_2O_5时,SrTiO_3陶瓷的电导率随 Nb_2O_5添加量的增加而增大,而 BaTiO_3陶瓷在0.15mol%附近出现最大值。烧结温度和冷却条件对 SrTiO_3陶瓷和添加量>0.15mol%的 BaTiO_3陶瓷的半导化都有很大影响。采取适当的冷却条件,也能使 Nb_2O_5添加量>0.15mol%的 BaTiO_3陶瓷的电阻率显著降低到10Ω·cm 左右。本文讨论了 BaTiO_3和 SrTiO_3陶瓷的半导化机理,认为 SrTiO_3陶瓷的半导化是施主离子所诱发出的晶格中的氧挥发所致,而 BaTiO_3陶瓷则由两种机制所控制。在 Nb_2O_5添加量<0.15mol%时,电价补偿起主要作用;当 Nb_2O_5含量增加到>0.15mol%时,就变成取决于冷却条件的氧挥发所控制。喇曼光谱实验也证明了这一点。     

阵列式半导体激光器中的热特性

本文给出了一组数学方程,以描述多条阵列式半导体激光器中的热特性,并针对具体实例进行了计算,将多条结构的结果同单条结构的结果进行了比较,发现前者带来管芯中发光区较高的温升。本文也讨论了阵列中电极条的宽度及条间距对管芯内温度分布的影响。     

Four-electron quantum dots in magnetic fields

Making use of hyperspherical coordinates, the energy spectrum of a four-electron configuration in a harmonic quantum dot (QD) as a function of the dot size and the strength of a magnetic field are investigated. Discontinuous ground-state transitions induced by an external magnetic field and the quantum dot size effect are shown. An important aspect of the size effect is the crossover of energy levels. The present results are useful to understand the optical and magnetic properties of QD materials.     

Low temperature synthesis of ZnSe nanoparticles

Synthesis of thioglycerol capped zinc selenide nanoparticles with a relatively narrow size distribution by a simple and inexpensive low temperature (~ 80 °C) wet chemical method is reported here. Main advantage of this method is the use of non-toxic precursors. The size of the nanoparticles can be varied easily by changing the concentration of the capping agent. The extracted nanoparticles remain stable under normal atmospheric conditions and can be redispersed in suitable solvents. The sharp absorption features obtained in the UV-Visible absorption spectra reveal the formation of monodispersed ZnSe nanoparticles. The nanoparticles were characterized using X-ray photoelectron spectroscopy, X-ray diffraction, UV-Visible absorption spectroscopy, photoluminescence and transmission electron microscopy.     

Influence of yttrium as a minority alloying element on the corrosion behavior in Fe-based bulk metallic glasses

The role of yttrium in corrosion behavior in an HCl solution was studied systematically by comparing bulk FeCrMoCB metallic glasses with and without yttrium. The corrosion resistance was very sensitive to minor yttrium addition. The material exhibits a detrimental effect on corrosion resistance at 0.5 at.% yttrium addition while a beneficial effect at more yttrium additions. Such effects are argued to be associated with variations of the semiconductor properties of passive film (i.e. defects concentration and band structure of passive film), induced by minority yttrium alloying element doping. It was shown that there exhibits a bi-layer structure of passive film on Fe-based metallic glasses. The outer layer with high valence cations is responsible for the dissolution behavior of the passive film, whereas the inner layer with doped oxides connects with the semiconductor properties. This result presents us an important hint that the corrosion resistance of metallic glasses can be improved by elaborately tailoring the defect structure of passive film via proper additions of minor alloying elements.