1550nm波长PNP型InGaAsP-InP异质结晶体管激光器材料设计与外延生长

基于器件模拟仿真,设计了一种PNP型1.5μm波长多量子阱InGaAsP-InP异质结晶体管激光器材料外延结构,并采用金属有机化学气相沉积外延生长.其中基区采用N型Si掺杂.因为扩散系数小,比较P型Zn搀杂具有较高的稳定性,因而较NPN结构外延材料容易获得高质量的光学有源区.由于N型欧姆接触比P型容易获得,基区搀杂浓度可以相对较低,有利于减小基区光损耗和载流子复合,从而获得较低的阈值电流和较高的输出光功率.所获得的外延材料呈现较高光-荧光谱峰值和65.1nm较低半峰宽.测试结果显示了较高的外延片光学质量.     

磷砷化镓黄色发光二极管

采用掺氨砷压法在磷化镓衬底上外延生长掺碲n型的GaAs0.15P0.85:N/GaP材料,制成磷砷化镓黄色发光二极管,测量了其光学和电学性能.讨论了影响器件发光效率的因素.     

2.0 μm 波段Sb基多量子阱材料的制备

采用分子束外延外延生长技术,优化InGaAsSb/AlGaAsSb多量子阱点材料的生长速率、生长温度和束流比等生长参数,获得了高质量的多量子阱材料。室温光荧光谱表明,材料的发光波长为2.0 m左右。该结果表明,通过优化生长条件和结构参数制备的量子阱材料,可以获得良好的结构质量和光学特性。所制备的器件室温条件下输出功率22 mW,阈值电流300 mA。     

1.5μm波长n-p-n型InGaAsP-InP晶体管激光器材料外延生长

基于器件模拟仿真,设计了一种1.5μm波长InGaAsP-InP晶体管激光器材料外延结构.其多量子阱有源区置于基区非对称波导中.仿真结果显示该外延结构能够获得较好的光场限制和侧向电流限制.对该材料MOCVD生长研究表明,基极重掺杂接触层中Zn2+扩散将导致量子阱严重退化.通过对其扩散过程的模拟仿真,采用平均掺杂浓度为1×1018cm-3的梯度掺杂,有效地抑制了Zn2+向量子阱区的扩散.所获得的外延材料在1.51μm呈现较强的PL峰值,具有卫星峰清晰的XRD谱.     

GaAs/SrTiO3外延半导体单晶薄膜带间跃迁研究

报道了在钙钛矿型结构的SrTiO₃衬底上用分子束外延方法生长闪锌矿型结构的GaAs半导体单晶薄膜.应用光调制反射光谱和光荧光方法 ,研究了GaAs半导体薄膜的带间跃迁,并与通常的GaAs体材料特性进行了对比研究.结果表明,在钙钛矿型结构SrTiO₃衬底上生长的GaAs单晶薄膜具有与单晶体材料相似的禁带与光学特性,在带间跃迁的弛豫上,外延薄膜相对体材料大了约5倍. 关键词：     

GaSb衬底上外延InAsxSb1-x材料的LP-MOCVD研究

采用自制的低压金属有机化学汽相淀积LP-MOCVD设备, 在(100)面GaSb单晶衬底上外延生长了InAsSb材料.用X射线双晶衍射、光学显微镜和扫描电镜、电子探针能谱仪等对材料特性进行了表征，分析研究了生长温度、Ⅴ/Ⅲ比、过渡层等对外延层的影响.并且获得了与GaSb衬底晶格失配度较低的表面光亮的晶体质量较好的InAsSb外延层.     

GaN基薄膜LED倒装芯片表面结构设计及光萃取效率研究

利用FDTD方法研究具有表面微纳结构氮化镓基倒装薄膜LED芯片的光萃取效率。通过优化表面结构并研究了器件的光萃取效率随p-Ga N层厚的变化。研究发现,具有表面光子晶体和六棱锥结构的器件的光萃取效率最大值比无表面微结构器件分别提高了56%和97%。尽管两种表面结构都能有效提高器件的光萃取效率,然而采用光子晶体的方案对p-Ga N厚度和腔长要求极为苛刻。采用六棱锥结构则不仅可以获得更高的光萃取效率,并且还将大大降低实验上材料外延生长及器件制备的难度。     

基于分布式布拉格反射器结构的空间三结砷化镓太阳能电池抗辐照研究

根据电子辐照条件下的常规三结砷化镓太阳能电池光谱响应以及电池电流的损伤特征, 确定电池衰减的物理机理: 中电池在电子辐照后形成的辐照损伤缺陷, 使得基区少子扩散长度被大幅缩短, 影响了光生载流子的收集. 针对中电池衰减的物理机理, 设计不同的基区厚度, 验证辐照后扩散长度缩短至1.5 μm左右. 为提升中电池抗辐照性能, 消除辐照后扩散长度缩减带来的影响, 对中电池外延结构进行设计, 将中电池基区减薄至1.5 μm, 并在其下方嵌入分布式布拉格反射器, 对特定波段光反射进行二次吸收, 弥补中电池减薄的影响. 通过TFCalc光学模系设计软件模拟出的中心波长为850 nm, 15对Al_0.9Ga_0.1As/Al_0.1Ga_0.9As的分布式布拉格反射器, 实际测试最高反射率大于97%, 高反带宽94 nm, 能够满足设计要求. 此基础上进行了新结构电池的外延生长与辐照测试对比. 实验结果表明: 新结构太阳能电池辐照后短路电流衰减比原结构降低了50%, 效率的剩余因子提升2.3%.     

p型透明导电材料BaSnO3的第一性原理研究

基于密度泛函理论,从头计算了N以及N和Sb共掺BaSnO₃的电子结构和光学性质.结果表明N单掺BaSnO₃与N和Sb共掺BaSnO₃均为p型透明导电材料,在可见光区透过率均在80%以上,且N和Sb共掺具有更高的电导率.计算结果为实验上制备p型钙钛矿结构透明导电材料提供了强有力的理论指导. 关键词： p型透明导电材料 电子结构 光学性质     

双外延基区4H-SiC BJTs的建模与仿真

基于4H-SiC的材料特性,对具有双外延基区结构的4H-SiC双极晶体管进行研究.通过分析该结构在基区内部形成的自建电场以及基区渡越时间,利用正交试验的方法,基于各种器件二维模型,对该器件结构进行数值计算,并进行平均极差分析.计算结果表明,该器件的共发射结电流增益最高可达72,具有负温度系数,并且在一个很宽的集电极电流范围内该特性保持不变.     

InP-based deep-ridge NPN transistor laser

We report an InP-based deep-ridge NPN transistor laser (TL, λ～1.5 μm). By placing the quantum well (QW) active material above the heavily Zn-doped base layer, both the optical absorption of the heavily p-doped base material and the damage of the quality of the QWs resulted from the Zn diffusion into the QWs are decreased greatly. CW operation of the TL is achieved at -40 °C, which is much better than the shallow-ridge InP-based NPN TL. With future optimization of the growth procedure, significant improvement of the performance of the deep-ridge InP-based NPN TLs is expected.     

Modeling of polysilicon diffusion sources during rapid optical annealing

A new model for polysilicon diffusion sources is presented. It considers the following effects: 1) dopant diffusion in grains, in grain boundaries and in the single-crystal silicon substrate, 2) dynamic dopant segregation between grain and grain boundary phases and between the phases of polysilicon and the single-crystal silicon substrate, 3) dynamic dopant activation or clustering in grains and in the single-crystal silicon substrate, 4) dynamic grain growth depending on local grain size and local electron density. These mechanisms with completely different time scales are modeled simultaneously. For the first time this allows the analysis of furnace and rapid optical annealing processes with arbitrary grain growth kinetics even during epitaxial realignment. The advanced model for segregation allows for the effect that dopants in grain boundaries and active dopants in grains as well as in the single-crystal silicon substrate find only a limited number of sites which can be occupied. These limitations are necessary to explain the dopant distributions in polysilicon and in the single-crystal silicon substrate. For the first time the coupling between the concentration of active dopants in grains, between the concentration of dopants in grain boundaries and between the local grain size is shown during doping enhanced grain growth.     

1,5-萘二胺衍生物的光谱分析及发光性能研究

合成了一种纯度较高的1,5-萘二胺衍生物(NPN),制备了NPN薄膜.利用紫外-可见吸收光谱和荧光发射光谱研究了NPN的发光行为,并结合电化学循环伏安法研究了其电子能级结构.结果表明,NPN的荧光光谱表现出明显的溶剂效应,认为其发生了从电子给体N原子到电子受体芳环之间的分子内电子转移,形成分子内电子转移络合物;从NPN薄膜与其溶液的吸收光谱峰值比较中看出吸收峰红移,认为薄膜中分子形成"J-聚集体";NPN的HOMO能级为-5.74 eV,光学禁带为2.79 eV;在365 nm紫外光的激发下,产生发光峰在448.6 nm附近、谱线带宽为72.6 nm的蓝光发射,发光亮度高,色纯度高.     

Efficient implementation of multiple drive-in steps in thermal diffusion of phosphorus for PERC solar cells

N-type phosphorus diffusion in silicon using phosphorus oxychloride, POCl₃, has been widely used in the production of p-type silicon solar cells. The thermal diffusion process in a furnace generally involves two steps: pre-deposition and drive-in. The phosphorous doping by thermal diffusion often shows high surface concentrations, leading to an increase in charge recombination, which should be inhibited in order to fabricate high efficiency silicon solar cells. In this study, we investigate the influence of 3 drive-in steps at sequentially increasing temperatures during the POCl₃ diffusion on the emitter performance. As a result, it was found that the kink region was made shorter while maintaining surface concentration for a good metal contact without losing its passivation quality. This result is attributed to the higher active dopant concentration of the 3 drive-in step samples, leading to a lower series resistance and higher fill factor in the PERC solar cells. The results show that slight changes in the PSG process conditions can contribute to the improvement of high efficiency solar cells.     

Doping of silicon with carbon during laser ablation process

The effect of laser ablation on properties of remaining material in silicon was investigated. It was found that laser cutting of wafers in the air induced the doping of silicon with carbon. The effect was more distinct when using higher laser power or UV radiation. Carbon ions created bonds with silicon atoms in the depth of the material. Formation of the silicon carbide type bonds was confirmed by SIMS, XPS and AES measurements. Modeling of the carbon diffusion to clarify its depth profile in silicon was performed. Photochemical reactions of such type changed the structure of material and could be the reason of the reduced machining quality. The controlled atmosphere was applied to prevent carbonization of silicon during laser cutting. PACS 52.38.Mf; 82.50.Hp; 82.80.Ms; 82.80.Pv     

基于第一性原理计算的掺杂柔性黑硅吸收光谱特性分析

针对宽波段微型光谱仪缺乏宽波段柔性探测器这一难题,提出了一种在紫外-可见-近红外波段内具有高吸收效率的掺杂柔性黑硅作为探测器吸光材料。首先,基于第一性原理计算了S和F元素掺杂后柔性黑硅的电子结构、能带结构和紫外-可见-近红外波段的光学吸收特性,得到了不同元素及浓度掺杂时,柔性黑硅的光学吸收系数。其次,将第一性原理计算结果与时域有限差分算法相结合,建立了柔性黑硅的吸收光谱模型。结果表明,掺入S和F元素后柔性黑硅的能带带隙均减小,吸收截止波长发生红移,且掺杂浓度越高,光学吸收系数越大。在1 500 nm波长处,50%浓度的S元素掺杂黑硅的吸光系数是1.5%浓度的S元素掺杂黑硅的吸光系数的8.3倍,50%浓度的F元素掺杂黑硅的吸光系数是1.5%浓度的F元素掺杂黑硅的吸光系数的3倍。在相同掺杂条件下,表面具有小尺寸微结构的柔性黑硅在近红外波段具有最高的吸收效率。最后,测试了制作的柔性黑硅样品,其吸光效率在紫外-可见波段高于95%,在近红外波段为70%~80%。     

硅薄膜太阳电池表面纳米线阵列光学设计

陷光结构的优化是增加硅薄膜太阳电池光吸收进而提高其效率的关键技术之一. 以硅纳米线阵列为代表的光子晶体微纳陷光结构具有突破传统陷光结构Yablonovith极限的巨大潜力. 通常硅纳米线阵列可以用作太阳电池的增透减反层、轴向p-n结、径向p-n结. 针对以上三种应用, 本文运用有限时域差分(FDTD)法系统研究了硅纳米线阵列在 300-1100 nm 波段的光学特性. 结果表明, 当硅纳米线作为太阳电池的减反层时, 周期P=300 nm, 高度H=1.5 μm, 填充率(FR)为0.282条件下时, 反射率最低为7.9%. 当硅纳米线作为轴向p-n结电池时, P=500 nm, H=1.5 μm, FR=0.55条件下纳米线阵列的吸收效率高达22.3%. 硅纳米线作为径向p-n结电池时, 其光吸收主要依靠纳米线, 硅纳米线P=300 nm, H=6 μm, FR= 0.349 条件下其吸收效率高达32.4%, 进一步提高其高度吸收效率变化不再明显. 此外, 本文还分析了非周期性硅纳米线阵列的光学性质, 与周期性硅纳米线阵列相比, 直径随机分布和位置随机分布的硅纳米线阵列都可以使吸收效率进一步提高, 相比于周期性硅纳米线阵列, 优化后直径随机分布的硅纳米线阵列吸收效率提高了39%, 吸收效率为27.8%. 本文运用FDTD法对硅纳米线阵列的光学特性进行设计与优化, 为硅纳米线阵列在太阳电池中的应用提供了理论支持.     

Si-based two-dimensional photonic crystals coupled to one-dimensional Bragg mirrors

Planar two-dimensional photonic crystals can be combined with a one-dimensional Bragg mirror to control the quality factor and out-of-plane coupling of optical Bloch modes. We have investigated the optical properties of such structures fabricated on silicon. The photonic crystals are fabricated in the upper Si layer deposited on top of quarter-wave thick SiO₂-polycrystalline Si layers. The optical properties are probed by the room-temperature photoluminescence of Ge/Si self-assembled islands as an internal source. We show that an enhancement of the quality factor can be obtained by controlling the thickness of the silicon upper layer in which the two-dimensional photonic crystal is etched and by controlling the air filling factor of the photonic crystal. Quality factors of 2200 around 1100 nm are obtained by this method for defect-free photonic crystals with a square lattice pattern. The experimental results are supported by three-dimensional finite-difference time-domain (FDTD) calculations of the radiated modes for the investigated structures.     

On the nature of point defects and the effect of oxidation on substitutional dopant diffusion in silicon

An extensive analysis of the substitutional dopant diffusion phenomena in silicon during oxidation is presented. The analysis covers qualitative as well as quantitative aspects of the oxidation-enhanced and -retarded diffusion (OED and ORD) phenomena, and examines three different possible assumptions that can be made on the nature of the silicon thermal equilibrium point defect species: silicon self-interstitials (I) only, vacancies (V) only, coexistence of I and V. The only consistent way to interpret all properly documented OED/ORD data is to assume that I and V coexist under oxidation as well as under thermal equilibrium conditions at high temperatures.     

射频等离子体增强化学气相沉积SiNx薄膜的研究

采用射频等离子体增强化学气相沉积技术,以N2和SiH4作为反应气体,在P型硅基片上进行SiNx薄膜的沉积.使用椭偏仪对薄膜厚度和光学常量进行了测量, 用傅里叶变换红外光谱仪对SiNx薄膜的化学键合结构进行了分析.研究了基片温度、射频功率以及N2和SiH4的气体流量比率等实验工艺参量对薄膜沉积速率和光学常量的影响.结果表明,射频等离子体增强化学气相沉积技术沉积的SiNx薄膜是低含氢量的SiNx薄膜,折射率在1.65~2.15之间,消光系数k在0.2~0.007之间,当SiNx薄膜为富氮时k≤0.01,最高沉积速率高达6.0 nm/min,N2和SiH4气体流量比率等于10是富硅和富氮SiNx薄膜的分界点.