Si基Ge异质结构发光器件的研究进展

近年来,与Si的CMOS工艺相兼容的Ge/Si异质结构发光器件取得很多重要的进展。本文概述了Si基Ge异质结构发光器件的最新成果,如Ge/Si量子点发光二极管、Si衬底上的Ge发光二极管及激光器和Ge/SiGe多量子阱发光二极管,分别描述了这些器件的特点和增强其发光特性的途径。最后展望了Si基Ge异质结构发光器件的发展趋势,指出尽管Si基Ge异质结构发光器件获得了很大的发展,但是器件的发光效率仍然很低,离实用还有一定距离,还需要在材料和器件的结构方面有更多的创新。     

21世纪的光学和光电子讲座第二讲 硅基发光材料和器件研究

硅基发光材料和器件是实现光电子集成的关键。文章评述了目前取得较大进展的几种主要硅基发光材料和器件的研究,包括掺饵硅,多孔硅,纳米硅以及Ｓｉ／ＳｉＯ２等超晶格结构材料,展望了这些不同硅基发光材料作为发光器件和在光电集成中的发展前景。     

纳米技术与能带工程对Si基高效发光的促进

自 1 991年CanhamL .T发现多孔Si的强发光特性之后 ,Si基发光的系列性探索已走过了 1 0年的路程。人们从中认清了一些重要的科学问题 ,发展和掌握了许多新的技术 ,也取得了许多有价值的重要进展。可以说过去的 1 0年是处於四方探索的百花齐放阶段。现在无论从应用目标的需求和开拓研究的思路与途径 ,都更加明确、集中 ,一个有实用价值的Si基发光器件的研究高潮即将来临。本文着重评述介绍了四个方面的研究进展 ,即局域态nc_Si的发光 ,基於能带工程的Si基发光 ,纳米结构Si化物的发光和Ge/Si量子点的发光研究 ,指出了各自存在的问题 ,提出了若干新的研究思路。本文还把Si基发光的研究与微电子发展需求紧密结合 ,由此提出了下一阶段开展Si基发光研究应予遵循的几项原则。     

21世纪的光学和光电子学讲座 第二讲 硅基发光材料和器件研究

硅基发光材料和器件是实现光电子集成的关键．文章评述了目前取得较大进展的几种主要硅基发光材料和器件的研究,包括掺饵硅,多孔硅,纳米硅以及Ｓｉ／ＳｉＯ２ 等超晶格结构材料．展望了这些不同硅基发光材料作为发光器件和在光电集成中的发展前景     

纳米技术与能带工程对Si基高效发光的促进

自1991年Canham L.T发现多孔Si的强发光特性之后，Si基发光的系列性探索已走过了10年的路程。人们从中认清了一些重要的科学问题，发现和掌握了许多新的技术，也取得了许多有价值的重要进展。可以说过去的10年是处於四方探索的百花齐放阶段，现在无论从应用目标的需求和开拓研究的思路与途径，都更加明确、集中，一个有实用价值的Si基发光器件的研究高潮即针来临。本文着重评述介绍了四个方面的研究进展，即局域态nc-Si的发光，基於能带工程的Si基发光，纳米结构Si化物的发光和Ge/Si量子点的发光研究，指出了各自存在的问题，提出了若干新的研究思路。本文还把Si基发光的研究与微电子发展需求紧密结合，由此提出了下一阶段开展Si基发光研究应予遵循的几项原则。     

硅基光电集成器件研究进展

随着器件结构与制作工艺的不断创新与完善，硅基发光器件已经可以实现室温下的有效工作，外量子效率可达到0．1％；低功耗的硅基高速调制器件的调制速率达到1GHz以上；而硅基光探测器对1300nm与1550nm波长的探测响应度也已分别达到了0．16mA／W和0．08mA／W．文章对硅基光电器件的研究进展情况进行了概述，并着重对几种器件的结构及工作原理进行了分析．     

金刚石紫外发光器件研究进展

蓝光或紫外激光在光电子学和光储存方面有广阔的应用，一直是国际上关注的前沿领域．而金刚石是最好的半导体紫外发光材料．特别是用于高温、高压、高功率、强辐射和强腐蚀环境中更能显示其优越性．目前人们已在实验上用同质外延、异质外延的方法制备了金刚石紫外发光二极管，观察到了较强的紫外光发射．人们尝试用金刚石与其他半导体材料结合的方法，成功地研制出了金刚石紫外发光二极管，开拓了该研究领域最新研究方向．文章对这些金刚石紫外发光器件研究的最新进展进行了评述．     

聚合物级联发光器件

基于溶液加工方法制备了聚乙撑二氧噻吩-聚(苯乙烯磺酸盐)(PEDOT∶PSS)/氧化锌(ZnO)/乙氧基化聚乙烯亚胺(PEIE)电荷产生层的聚合物级联发光器件, 发现PEDOT∶PSS层电导和厚度对器件的电流-电压特性影响较小, 不同PEDOT∶PSS对器件发光效率的影响主要来自于其对发光层激子不同的猝灭作用, PEDOT∶PSS厚度为60 nm的级联器件比PEDOT∶PSS 厚度为30 nm的级联器件的发光效率稍高, 原因是PEDOT∶PSS较厚时, 其表面形貌更均匀。级联器件的发光效率和驱动电压分别与发光子单元的发光效率和驱动电压之和相近, 说明在较低的电压下电荷产生层就能够有效产生电荷并注入到发光子单元中,级联器件的发光光谱中包含两个发光子单元的发光光谱,说明两个发光子单元在级联器件中都能正常工作。通过对电荷产生层的电容-电压(C-V)特性的测试, 确认了在电荷产生层中存在电荷的积累过程。证明了PEDOT∶PSS/ZnO/PEIE为有效的电荷产生层。首次报道了包含三个SY-PPV发光单元的级联器件, 三个发光子单元发光效率之和与级联器件的发光效率相当, 其最大发光效率和最大外量子效率分别为21.7 cd·A-1和6.95%。在器件亮度为5 000 cd·m-2时, 器件的发光效率和外量子效率分别为20.5 cd·A-1和6.6%。说明并没有由于发光子单元数目增加而影响级联器件的发光效率。并且其发光光谱和发光子单元的发光光谱相接近。通过 进一步降低CGL中空穴注入层对级联器件的影响有望提高级联器件的发光效率。     

超薄发光层结构的荧光型白光有机发光器件

使用蓝、绿、红超薄发光层结构来制备荧光型非掺杂白光器件,其器件结构为ITO/MoO3(5 nm)/TCTA(40 nm)/C545T(1 nm)/TCTA(2 nm)/BePP2(1 nm)/Bphen(2 nm)/DCJTB(1 nm)/Bphen(30 nm)/LiF(1nm)/Al(1 000 nm).白光器件的最大发光亮度和电流效率分别为16 154.73 cd/m2和11.58 cd/A.在电压为7V时,器件的色坐标为(0.322 2,0.335 1),而且色坐标在大的电压变化范围内的变化值仅为(0.017 4,0.002 9).与掺杂结构的白光器件相比,超薄发光层结构的白光器件拥有高的电流效率和稳定的电致发光光谱,原因是超薄发光层结构的载流子捕获效应能使激子有效限制在复合区域内.     

Si(001)衬底上分子束外延生长Ge0.975Sn0.025合金薄膜

使用低、高温两步法生长的高质量Ge薄膜作为缓冲层,在Si(001)衬底上采用分子束外延法生长出Ge_0.975Sn_0.025合金薄膜.X射线双晶衍射和卢瑟福背散射谱等测试结果表明,Ge_0.975Sn_0.025合金薄膜具有很好的晶体质量,并且没有发生Sn表面分凝.另外,Ge_0.975Sn_0.025合金薄膜在500 ℃下具有很好的热稳定性,有望在Si基光电器件中得到应用. 关键词： GeSn Ge 分子束外延 外延生长     

Formation of high-Sn content polycrystalline GeSn films by pulsed laser annealing on co-sputtered amorphous GeSn on Ge substrate

Polycrystalline Ge_(1-x)Sn_x(poly-Ge_(1-x)Sn_x) alloy thin films with high Sn content( 10%) were fabricated by cosputtering amorphous GeSn(a-GeSn) on Ge(100) wafers and subsequently pulsed laser annealing with laser energy density in the range of 250 mJ/cm~2 to 550 mJ/cm~2. High quality poly-crystal Ge_(0.90) Sn_(0.10) and Ge_(0.82) Sn_(0.18) films with average grain sizes of 94 nm and 54 nm were obtained, respectively. Sn segregation at the grain boundaries makes Sn content in the poly-GeSn alloys slightly less than that in the corresponding primary a-GeSn. The crystalline grain size is reduced with the increase of the laser energy density or higher Sn content in the primary a-GeSn films due to the booming of nucleation numbers. The Raman peak shift of Ge-Ge mode in the poly crystalline GeSn can be attributed to Sn substitution, strain,and disorder. The dependence of Raman peak shift of the Ge-Ge mode caused by strain and disorder in GeSn films on full-width at half-maximum(FWHM) is well quantified by a linear relationship, which provides an effective method to evaluate the quality of poly-Ge_(1-x)Sn_x by Raman spectra.     

Temperature dependent direct-bandgap light emission and optical gain of Ge

Band structure, electron distribution, direct-bandgap light emission, and optical gain of tensile strained, n-doped Ge at different temperatures were calculated. We found that the heating effects not only increase the electron occupancy rate in the Γ valley of Ge by thermal excitation, but also reduce the energy difference between its Γ valley and L valley. However,the light emission enhancement of Ge induced by the heating effects is weakened with increasing tensile strain and n-doping concentration. This phenomenon could be explained by that Ge is more similar to a direct bandgap material under tensile strain and n-doping. The heating effects also increase the optical gain of tensile strained, n-doped Ge at low temperature, but decrease it at high temperature. At high temperature, the hole and electron distributions become more flat, which prevent obtaining higher optical gain. Meanwhile, the heating effects also increase the free-carrier absorption. Therefore, to obtain a higher net maximum gain, the tensile strained, n-doped Ge films on Si should balance the gain increased by the heating effects and the optical loss induced by the free-carrier absorption.     

GeSn (0.524 eV) single-junction thermophotovoltaic cells based on the device transport model

Based on the transport equation of the semiconductor device model for 0.524 eV GeSn alloy and the experimental parameters of the material, the thermal-electricity conversion performance governed by a GeSn diode has been systematically studied in its normal and inverted structures. For the normal p⁺/n (n⁺/p) structure, it is demonstrated here that an optimal base doping N_d(a) = 3 (7)×10¹⁸ cm^-3 is observed, and the superior p⁺/n structure can achieve a higher performance. To reduce material consumption, an economical active layer can comprise a 100 nm-300 nm emitter and a 3 μm-6 μm base to attain comparable performance to that for the optimal configuration. Our results offer many useful guidelines for the fabrication of economical GeSn thermophotovoltaic devices.     

在Si衬底上自组装生长Ge量子点研究进展

在Si衬底上自组装生长纳米尺度的Ge量子点，由于三维量子限制效应的贡献，能够在能带结构上对Si、Ge天然材料的间接带特性实施准直接带结构的改性，使激子行为和带间复合跃迁得到大幅度增强，同时Ge量子点的可控有序相关排列还有助于发展新一代的Si基电子波量子器件．文章回顾了自20世纪80年代末至今Ge／Si量子点生长研究的重要进展，对其潜在的重要应用作出了评述．结合作者自己的研究结果，着重介绍了Ge量子点的生长动力学及其形态的演变过程，指出自组装生长的Ge／Si量子点属Ⅱ型能带结构，其发光效率比一维量子阱有很大增强．探讨了用模板衬底实现对Ge量子点尺寸和分布的有序可控生长方法与途径．     

Study of irradiation induced changes of electrical and functional characteristics in Ge doped Si diodes

P-on-n diodes fabricated on n-type Cz Si wafers with different Ge doping concentrations were irradiated with 2 MeV electrons and 1 MeV equivalent reactor neutrons using a wide range of fluences and examined by combining current and capacitance transient techniques.     

Formation of Ge islands from a Ge layer on Si substrate during post-growth annealing

We have deposited a 12 nm thick Ge layer on Si(1 0 0) held at 200 °C by thermal evaporation under high vacuum conditions. Upon subsequent thermal annealing in vacuum, self-assembled growth of nanostructural Ge islands on the Ge layer occurred. Atomic force microscopy (AFM) and grazing incidence small-angle X-ray scattering (GISAXS) were used to characterize such layers. GISAXS measurements evidenced the formation of cylinder shaped structures upon annealing at 700 °C, which was confirmed by AFM measurements with a very sharp tip. A Ge mass transport from the layer to the islands was inferred by X-ray reflectivity and an activation energy of 0.40 ± 0.10 eV for such a process was calculated.