Defect Modulation Doping

The doping of semiconductor materials is a fundamental part of modern technology, but the classical approaches have in many cases reached their limits both in regard to achievable charge carrier density as well as mobility. Modulation doping, a mechanism that exploits the energy band alignment at an interface between two materials to induce free charge carriers in one of them, is shown to circumvent the mobility restriction. Due to an alignment of doping limits by intrinsic defects, however, the carrier density limit cannot be lifted using this approach. Here, a novel doping strategy using defects in a wide bandgap material to dope the surface of a second semiconductor layer of dissimilar nature is presented. It is shown that by depositing an insulator on a semiconductor material, the conductivity of the layer stack can be increased by 7 orders of magnitude, without the necessity of high‐temperature processes or epitaxial growth. This approach has the potential to circumvent limits to both carrier mobility and density, opening up new possibilities in semiconductor device fabrication, particularly for the emerging field of oxide thin film electronics.     

半导体中掺杂缺陷的研究

研究了近年来有关含杂质、杂质对或多杂质缺陷半导体的状况。     

一维缺陷光子晶体的模式特性研究

利用光学传输矩阵方法研究对称和非对称一维缺陷光子晶体的缺陷模式特性。研究发现：1个缺陷可以导致光子禁带中出现多个缺陷模式；缺陷夹层厚度为零时，非对称结构中缺陷模消失，而对称结构中仍然存在缺陷模；两种结构的缺陷模式数目以及每个缺陷模的位置波长值均与缺陷夹层的光学厚度按正比例关系增加；两种结构的模式移动速度基本相等，并且与缺陷模式的阶数按反比例规律下降。     

Intrinsic Surface and Bulk Defect Modes in Quasi-Periodic Photonic Crystals

By analyzing resonances in the local density of states (LDOS) for a fivefold 2-D quasi-periodic photonic crystal (QPC), we reveal the presence of a well-defined number of defect modes in the spectral region of a low LDOS, which are intrinsic to this class of photonic structures. We may distinguish between surface modes, depending on the truncation of the finite-sized structure, and bulk modes. All defects can be traced to a configuration of closely spaced cylinders. Due to mutual coupling, their collective eigenresonance is strongly shifted into the spectral region of a low LDOS, and they appear as defect modes, which are comparable to acceptor modes in periodic photonic crystals. Control over the geometrical parameters of such resonators allows for a simple adjustment of the defect mode frequencies in QPCs.     

多掺杂一维各向异性光子晶体的缺陷特性

为了研究多掺杂一维各向异性光子晶体的光学特性,采用传输矩阵法计算了光波通过多掺杂一维各向异性光子晶体的透射率。经数值模拟得到:光通过该结构光子晶体后,TE波和TM波的透射谱中随掺杂层个数的变化出现了单、双及多缺陷模,禁带中缺陷模的个数随掺杂层数的增大而增多,缺陷模的位置随掺杂层光学厚度的变化向短波方向移动,TE波和TM波的缺陷模能完全分开,透射谱的这一特点为设计制作单、双通道滤波器提供了理论依据。     

一维掺杂光子晶体缺陷模的全貌特征

通过一维掺杂光子晶体缺陷模的三个不同角度的立体图以及它们对应的俯视切面图,全面地研究了缺陷模随杂质光学厚度、杂质折射率以及光子晶体折射率的变化关系,得出了一维掺杂光子晶体缺陷模的全貌特征,并得到以下重要结论:缺陷模透射峰随杂质光学厚度变化呈周期性的出现,在同一周期上缺陷模的波长随杂质光学厚度呈线性变化;缺陷模透射峰的半高宽度随杂质折射率的增加而减小,但陷模透射峰的高度不受杂质折射率变化的影响;光子晶体的折射率对缺陷模透射峰的峰高和半高宽度都有显著的影响.     

受主掺杂对TiO2氧敏材料缺陷化学的影响

对受主B2O5掺杂TiO2材料的高温电导进行了详细的测试；XRD分析表明少量受主掺杂并未改变材料的金红石结构；对比施主掺杂研究，出现了很多有趣的现象。施主掺杂样品在较高的测试温度（约950℃）下发生电导类型转变，而受主掺杂样品在较低的测试温度（约750℃）下发生电导类型转变。应用电子补偿及缺位补偿机制对电导特性进行了分析。     

施主掺杂对TiO2氧敏材料缺陷化学的影响

对施主V2O5掺杂TIO2材料的高温电导进行了详细的测试：XRD分析表明少量施主掺杂并未改变材料的金红石结构；施主掺杂样品在较高温度测试时，在高氧分压一侧，发生电导类型转变，从而使测氧范围变窄。运用缺陷化学分析法，解释了不同氧分压下的电导机制。     

Molecular Self‐Doping Controls Luminescence of Pure Organic Single Crystals

Organic optoelectronics calls for materials combining bright luminescence and efficient charge transport. The former is readily achieved in isolated molecules, while the latter requires strong molecular aggregation, which usually quenches luminescence. This hurdle is generally resolved by doping the host material with highly luminescent molecules collecting the excitation energy from the host. Here, a novel concept of molecular self‐doping is introduced in which a higher luminescent dopant emerges as a minute‐amount byproduct during the host material synthesis. As a one‐stage process, self‐doping is more advantageous than widely used external doping. The concept is proved on thiophene–phenylene cooligomers (TPCO) consisting of four (host) and six (dopant) conjugated rings. It is shown that <1% self‐doping doubles the photoluminescence in the TPCO single crystals, while not affecting much their charge transport properties. The Monte‐Carlo modeling of photoluminescence dynamics reveals that host–dopant energy transfer is controlled by both excitonic transport in the host and host–dopant Förster resonant energy transfer. The self‐doping concept is further broadened to a variety of conjugated oligomers synthesized via Suzuki, Kumada, and Stille crosscoupling reactions. It is concluded that self‐doping combined with improved excitonic transport and host–dopant energy transfer is a promising route to highly luminescent semiconducting organic single crystals for optoelectronics.     

一维多层掺杂光子晶体缺陷模的偏振特性

为了研究多层掺杂对一维光子晶体缺陷模偏振特性的影响,采用特征矩阵法计算了一维光子晶体双层掺杂和三层掺杂情况下缺陷模的偏振特征.结果表明:双层掺杂时,TE波和TM波都出现了两个缺陷模,两个缺陷模随入射角的增加向短波方向移动,TE波的两个缺陷模随入射角的增加而减弱,而TM波的两个缺陷模随入射角的增加而增强.三层掺杂时,TE波和TM波也都出现了两个缺陷模,但比两层掺杂的缺陷模要弱,TE波和TM波的两个缺陷模随入射角的变化特征与双层掺杂的情况相似.     

一种缓变结构一维光子晶体的缺陷模研究

利用传输矩阵方法,研究了单折射率层缓变准周期结构一维光子晶体存在不同缺陷时的缺陷模。结果表明,当该准周期结构中存在缺陷时,引入了缺陷模,且缺陷模与缺陷层的位置和结构参数相关。缺陷层不同,缺陷模的位置及共振透射峰也不同。随着缺陷层光学厚度的增大,缺陷模波长向长波方向移动。     

负折射率缺陷层光子晶体的缺陷模和光学增强

研究了缺陷层为负折射率材料的一维光子晶体的带隙结构.研究结果表明：与缺陷层为正折射率材料的同类型结构相比,负折射率材料缺陷模的宽度变宽,且随着缺陷层厚度的增加,缺陷模向高频（短波）方向移动,缺陷模的移动速度也大.同时研究了负折射率缺陷层位置的不同对光子晶体透射特性的影响以及光学增强效应.     

Artificial Defect Engineering in Three‐Dimensional Colloidal Photonic Crystals

Artificial defect engineering in 3D colloidal photonic crystals is of paramount importance in terms of device applications. Over the past few years, we have carried out a great deal of research on introducing artificial defects, including point, line, and planar defects, in 3D colloidal photonic crystals by using “bottom‐up” self‐assembly in combination with “top‐down” micromachining techniques. In this Feature Article, we summarize our research results regarding the engineering of artificial defects in self‐assembled 3D photonic crystals, along with other important research breakthroughs in the literature. The significant advancements in the engineering of defects as reviewed here together with the encouraging reports on the fabrication of perfect colloidal crystals without unwanted defects will collectively lead to technological applications of self‐assembled 3D photonic crystals in the near future.     

利用转移矩阵法和频域块迭代法分析点缺陷二维光子晶体

本文介绍了广泛用于分析光子晶体的两种方法；转移矩阵法和频域块迭代法。运用这两种方法，我们研究了一个5行5列在空气中呈正方排列的二维介质柱晶体，改变中心介质柱的半律和介电常数，分别得到各自对应不同的透射和色散关系曲线，对于同一参数结构的光子晶体，不同算法得到的带隙和缺陷态频率是一致的。同时根据透射和色散曲线所体现出来的晶体特性，我们分析了将光子晶体用作激光谐振腔以提高Q值的机理。     

一种准周期结构一维光子晶体的缺陷模研究

利用传输矩阵方法,研究了单折射率层缓变准周期结构一维光子晶体存在不同缺陷时的缺陷模.研究表明,无论缺陷层是替代高折射率层,还是替代低折射率层,都会引入缺陷模,且缺陷模与缺陷层的位置和结构参数相关.缺陷层位置不同,缺陷模的位置及共振透射峰也不同.随着缺陷层光学厚度的增大,缺陷模波长向长波方向移动.但缺陷模品质因子却随缺陷层替代不同的折射率层而存在差异,这一差异是同所计算的一维光子晶体自身的结构相关的.     

光子晶体结构、制备技术和应用进展

介绍了光子晶体的结构、制备技术和应用方面的最新进展。继金刚石结构之后,又证实了圆木堆积、反蛋白石和矩形螺旋结构具有完全光子带隙。光子晶体的制备技术大体可分为微电子制备技术、自组装技术与层层叠加技术,三者各有优缺点。光子晶体在光子晶体光纤、光子晶体激光器、光子晶体波导等众多领域有着广阔的应用前景。     

香蕉型液晶的电子结构计算和电激发特性

用舒克紧束缚法计算了一种新型香蕉型液晶1,3-phenylene bis [4-(4′-nonyloxy) phenyliminomethyl] benzoate 的电子结构,结果表明: LUMO和HOMO的能量差别主要是受到香蕉型液晶的中心核、桥键(-COO-)的影响,而烷基尾对香蕉型液晶电子结构的影响不大;在6种可能跃迁中,只有能量最低的两种(π→π*, n→π*)在200~800 nm可见光范围内是经常发生的.对于这种香蕉型液晶,电子激发主要发生在4.0 eV (310 nm)和 1.7 eV (730 nm)处.     

Scattering Matrix Method for Modeling Defect Modes in 2-D Photonic Crystals

A novel and numerically efficient treatment of electromagnetic modes localized at defects in two-dimension (2D) photonic crystals is presented in this paper. The method represents the fields in terms of scattered fields by each column of the photonic crystals. With the method, the field distributions in two photonic crystal structures are calculated with satisfying results.     

用散射短阵法求二维光子晶体缺陷内的场分布

本文介绍了一种新颖而高效的计算位于二维光子晶体缺陷中电磁场模式的方法，这一方法是通过将光子晶体中每个柱体的散射场叠加起来而得到所求场的，用该方法计算了两例具体的光子晶体结构，得到了满意的结果。     

杂质吸收对光子晶体缺陷模偏振态的影响

引入复折射率并利用特征矩阵法,研究了杂质的吸收对TE波和TM波缺陷模透射峰的影响.得出:杂质的消光系数对TE波和TM波的缺陷模透射峰都有显著的影响,但对TE波缺陷模的影响比对TM波缺陷模的影响更为明显.当消光系数一定时,TE波的缺陷模透射峰随入射角的增大而迅速减小,而TM波的缺陷模透射峰随入射角的增大而增大.利用这一特性可以设计光子晶体偏振滤波器.