实时全息干涉计量术的发展近况和趋势

本文综述了实时全息干涉计量术的发展近况。介绍了实时全息干涉计量术的某些新方法,新装置及其所依据的原理并论述其发展趋势。     

MOCVD生长的CdZnTe／ZnTe多量子附的激子光学特性

用常压ＭＯＣＶＤ方法在ＧａＡｓ（１００）衬底上生长了ＣｄＺｎＴｅ／ＺｎＴｅ多量子阱。在室温下，观测到了ＣｄＺｎＴｅ／ＺｎＴｅ多量子阱的三个谱带发光。根据ＣｄＺｎＴｅ／ＺｎＴｅ多量子阱的吸收光谱和不同激发光强下的发光光谱，分别归结ＣｄＺｎＴｅ／ＺｎＴｅ多量子阱中观测到的三个发光谱带于覆盖层发光、ｎ＝１的重空穴激子发光及杂质发光。     

High thermoelectric figures of merit in PbTe quantum wells

High-quality Pb_1−xEu_xTe/PbTe multiple quantum wells (MQWs) have been grown by molecular beam epitaxy. The measured 300K thermoelectric properties have been compared with that of the best bulk PbTe. This experimental investigation is the first detailed study of MQW structures designed to improve ZT of thermoelectric materials and has resulted in a breakthrough in the decades-long ZT ≅ 1 barrier for a room-temperature thermoelectric material. A value of Z_2DT >1.2 has been achieved for these PbTe quantum wells.     

单边凹槽电极结构MSM型蓝光探测器的研究

为提升InGaN基可见光探测器性能,制作并测试了基于GaN/InGaN MQWs外延材料的单边凹槽叉指电极MSM结构蓝光光电二极管。凹槽电极器件的I-V特性测试结果显示,相较于传统平面电极器件,随着偏压增加,器件暗电流越小且越趋于平缓,而光电流越大;光谱响应率测试显示,器件截止带边都位于490nm附近,凹槽电极器件带边处拒绝比高于平面电极器件1个量级。当偏压为5V时,凹槽电极器件响应率为0.0346A/W@480nm,对应外量子效率为8.94%,高于平面电极器件。器件性能提升的原因是单边凹槽电极结构有效改善了内建电场的分布,从而抑制了表面传导漏电流,使得器件暗电流更小且更有利于电极收集光生载流子,提升了响应率。     

Analysis Expression of Rate Equation for Vertical Cavity Lasers

An analysis solution of rate equation is derived for vertical cavity surface-emitting lasers.Based on the enhanced spontaneous emission caused by VCSELs and influence of nonradiative recombination, the relation between output properties and structural parametersof multi-quantum wells(MQWs) is obtanined.It was found that the characteristic curve of a “thresholdless“ laser is strongly nonradiative depopulation-dependent.When the nonradiative depopulation is no zero,the light-current characteristic is not linearly even for an ideal closed microcavity.The light output is increased by the enhanced well number and by the reduced width.In particular, a lower threshold current density for MQWs structure in the short cavity is realized by us, meanwhile the sharpness of the variation depends on spontaneous emission factor.     

掺Si对AlGaInP/GaInP多量子阱发光性能的影响

研究了Si掺杂对MOCVD生长的（Al0.3Ga0.7）In0.5P/Ga0.5In0.5P多量子阱发光性能的影响．样品分为两类：一类只生长了（Al0.3Ga0.7）In0.5P/Ga0.5In0.5P多量子阱结构;另一类为完整的多量子阱LED结构．对于只生长了（Al0.3Ga0.7）In0.5P/Ga0.5In0.5P多量子阱结构的样品,掺Si没有改变量子阱发光波长,但使得量子阱发光强度略有下降,发光峰半高宽明显增大．这应是掺Si使量子阱界面质量变差导致的．而在完整LED结构的情况下,掺Si却大大提高了量子阱的发光强度．相对于未掺杂多量子阱LED结构,垒层掺Si使多量子阱的发光强度提高了13倍,阱层和垒层均掺Si使多量子阱的发光强度提高了28倍,并对这一现象进行了讨论．     

MOCVD生长Al0.48Ga0.52N/Al0.54Ga0.36N多量子阱的结构和光学特性

采用金属有机物化学气相淀积(MOCVD)技术,在蓝宝石衬底上生长了Al0.48Ga0.52N/Al0.54Ga0.36N多量子阱(MQWs)结构。通过双晶X射线衍射(DCXRD)、原子力显微镜(AFM)和阴极荧光(CL)等测试技术,分别对样品的结构和光学特性进行了表征。在DCXRD图谱中,可以观察到明显的MQWs衍射卫星峰,通过拟和,MQWs结构中阱和垒的厚度分别为2.1和9.4nm,Al组分分别为0.48和0.54。在AFM表面形貌图上,可以观察到清晰的台阶流,表明MQWs获得了二维生长;与此同时,MQWs结构存在一些裂缝,主要原因为AlGaNMQWs结构和下层GaN层间存在很大的应力。CL测试表明,AlGaNMQWs结构的发光波长为295nm,处于深紫外波段,同时观察到处于蓝光、绿光波段的缺陷发光。     

High quality GaN-based LED epitaxial layers grown in a homemade MOCVD system

A homemade 7×2 inch MOCVD system is presented.With this system,high quality GaN epitaxial layers,InGaN/GaN multi-quantum wells and blue LED structural epitaxial layers have been successfully grown. The non-uniformity of undoped GaN epitaxial layers is as low as 2.86%.Using the LED structural epitaxial layers, blue LED chips with area of 350×350μm~2 were fabricated.Under 20 mA injection current,the optical output power of the blue LED is 8.62 mW.     

Design and fabrication of InxGa1 − xN/GaN solar cells with a multiple-quantum-well structure on SiCN/Si(111) substrates

The fabrication and characterization of In_xGa_1 − xN/GaN-based solar cells that use In_xGa_1 − xN multiple quantum wells (MQWs) and a SiCN/Si(111) substrate are reported. Solar cell operation with a low dark current density (J_d), a high open-circuit voltage (V_oc), a high short-circuit current density (J_sc), and a high fill factor (FF) is demonstrated. It was found that the proposed device and fabrication technology are applicable to the realization of solar cells with a low J_d of 2.14 to 8.88 μA/cm², a high V_oc of 2.72 to 2.92 V, a high J_sc of 2.72 to 2.97 mA/cm², and a high FF of 61.51 to 74.89%. The device performance with various quantum-well configurations was investigated under an air mass 1.5 global solar spectrum. A high photovoltaic efficiency of 5.95% in the MQW sample over the p-i-n sample was observed.     

应变多量子阱激光器的结构稳定性

通过计算应变多量子阱中的净应力和应变弛豫,讨论了激光器结构中应变多量子阱的稳定性。净应力是失配位错增殖的驱动力,是应变多量子阱稳定的重要判据。因此,用单结点模型计算了应变多量子阱结构中的净应力。计算结果表明,净应力的最大值在应变多量子阱结构中的位置与阱层和垒层的厚度以及阱层的失配有关,非应变垒层和盖层能在一定程度上稀释净应力。在此基础上,利用动力学模型计算了应变多量子阱的应变弛豫。