GaAs three-terminal double delta-doped triangular barrier switch prepared by molecular beam epitaxy

A novel S-shaped negative differential resistance (NDR) switching device, prepared by molecular beam epitaxy (MBE), has been successfully developed in a GaAs double delta-doped triangular barrier (TB) structure. All symmetrical S-shaped NDR characteristics, either unidirectional or bidirectional bistability phenomena, are observed experimentally. The bidirectional current-voltage (I–V) characteristics exhibit a new type of NDR caused by an avalanche multiplication process in the reverse-biased base-collector region and by barrier redistribution. Under a base current injection with respect to the cathode, the device behaves as a conventional transistor with a current gain of 1.2 at room temperature. Experimentally, electrical results can be easily understood by an equivalent circuit and a proposed model. In addition, a new optoelectronic switching device is also proposed which may have the potential for bidirectional wavelength emission. On the basis of the first utilization of a double delta-doped TB structure, a conceptual understanding of such a set of results enhances our understanding of the physics of double delta-doped TB devices in general.     

浅析数学教学中意志品质的培养

在数学教学中,除了让学生掌握数学的基本知识和基本方法外,还应帮助学生形成良好的心理品质,其中意志品质的培养尤为重要。学生意志品质的优劣对实现教学目的,完成教学任务起着重要作用。本文针对数学教学中如何培养学生的意志品质展开讨论。     

Investigation of thermal effects on the single-finger heterojunction bipolar transistors

We will first derive a physics-based, analytical single-finger heterojunction bipolar transistor (HBT) model which takes into account the thermal effect. Next, the model is used to calculate the three figures of merit of HBT, i.e., current gain, cut-off frequency and maximum frequency. Their variation against the collector current density under the influence of thermal effect is presented and the calculation results are discussed.     

氰化钠药剂制备与自动添加技术在四方金矿的应用

通过对氰化钠药剂制备与添加系统中存在问题的分析与研究,对其进行技术改造,通过改造,稳定了制备药剂的＇浓度,更能精确控制浸出系统的CN质量浓度,稳定了生产工艺;降低了氰化钠的消耗,降低了选矿成本,实现了节支降耗的目的,取得了良好的经济效益。     

镀银纤维混纺织物抑菌性能及机理分析

探讨棉镀银纤维混纺织物的抑菌性能及机理。采用不同含银量的镀银纤维与棉纤维纺制不同混纺比的棉镀银纤维混纺纱,并织制出不同含银量的棉镀银纤维混纺织物,测试了不同含银量、不同洗涤次数、与大肠杆菌不同接触时间的混纺织物对大肠杆菌的抑菌效果,同时测试了不同浸泡时间下混纺织物的银离子释放率。研究结果表明:棉镀银纤维混纺织物中的含银量在2%以上时,其对大肠杆菌的抑菌率可以达到100%;镀银纤维中的银含量、棉镀银纤维混纺比对混纺织物的抑菌效果均有明显的影响;镀银纤维的抑菌效果和镀银纤维表面沉积银层的离子化有关,银离子释放率越高,抑菌效果越明显。     

Negative differential resistance of a delta-doping-induceddouble-barrier quantum-well diode at room temperature

A resonant-tunneling homojunction diode, which is a delta-doping-induced double-barrier quantum-well (D³BQW) diode, is presented. The barrier uses the δn⁺-i-δp⁺-i-δn⁺ structure. The current-voltage characteristics exhibit three sections of negative differential resistance (NDR) phenomena. At low bias, N-type NDR is demonstrated due to the resonant-tunneling effect. At higher bias, another N-type NDR appears due to the heating effect in the high electric field. As the external bias increases further, an S-type NDR is observed. This result is attributed to the impact ionization effect of thermionic electrons, and then trapping of holes in the maxima of the valence bands, resulting in barrier lowering and redistribution of voltage     

Room temperature operation of a GaAs tristate switch with a double triangular barrier structure

A new GaAs double triangular barrier (DTB) switch, prepared by molecular-beam epitaxy (MBE), using p⁺-n-(p⁺)-n-(p⁺)-n-n⁺ structure was fabricated and demonstrated. A tristate switching behaviour due to the sequential collapse of internal barriers was clearly observed for the first time. This phenomenon introduced triple stable regions into the device operation. Based on a proper circuit design, the structure studied has good potential for tristate-logic applications.     

Enhanced characteristics in gate-recessed and sidewall-recessed AlGaAs/InGaAs PHEMTs by citric-based selective wet etching

Improved device performance in Al_0.2Ga_0.8As/In_0.15Ga_0.85As gate-recessed enhancement-mode pseudomorphic high electron mobility transistors (E-PHEMTs) and sidewall-recessed depletion-mode PHEMTs (D-PHEMTs) using a newly developed citric buffer etchant are reported. The innovated etchant near room temperature (23°C) possesses a high GaAs/Al_0.2Ga_0.8As or In_0.15Ga_0.85As/Al_0.2Ga_0.8As etching selectivity (>250) applied to an etched stop surface. For E-PHEMTs, the transconductance (G_m) of 315?mS/mm and high linearity of 0.46?V-wide gate voltage swing (drop of 10% peak G_m), corresponding to 143?mA/mm-wide I_DS, even at a gate length of 1?µm is obtained. For microwave operation, this 1?µm-gate E-PHEMT shows the f_max (maximum operation frequency) of 29.2?GHz and the f_T (cut-off frequency) of 11.2?GHz, respectively. The measured minimum noise figure (NF_min), under V_DS?=?3?V and I_DS?=?7.5?mA, is 0.56?dB at 1?GHz with the associated gain of 10.86?dB. The NF_min is less than 1.5?dB in the frequency range from 1 to 4?GHz. In addition, an effective and simple method of selective gate sidewall recess is utilized to etch the low barrier in In_0.15Ga_0.85As channel at mesa sidewalls for D-PHEMTs. For D-PHEMTs with 1?×?100?µm² exhibit a very low gate leakage current of 2.4?μA/mm even at V_GD?=??10?V and high gate breakdown voltage over 25?V. As compared to that of no sidewall recess, nearly two orders of reduction in magnitude of gate leakage current and 100% improvement in gate breakdown voltage are achieved.     

桑蚕膨松丝及其针织产品的开发研究

介绍了桑蚕膨松丝的主要性，利用这种新形质生丝开发真丝针织物新品种及工艺条件，对共织物性能与风格进行了测试和分析，从测试结果说明桑蚕膨松丝是一种品质优良，特别适用于真丝针织的丝绸新材料。     

New tri-state switch (TSS) using AlGaAs/GaAs/InGaAs double heterostructure

A new AlGaAs/GaAs/InGaAs heteroconfinement tri-state switch (TSS) prepared by metal organic chemical vapor deposition has been fabricated and demonstrated. This TSS exhibits the interesting multiple negative differential resistance (MNDR) characteristics. The NDR behavior is caused by a p ⁺ n junction and sequential two-stage barrier-lowering and potential-redistribution effect that resulted from the electron confinement at AlGaAs/GaAs/InGaAs heterointerface and lnGaAs quantum well, respectively.