用光电流谱研究多孔硅微腔的光电特性

利用光电流谱对全硅基多孔硅微腔的吸收特性进行了研究 ,在光电流谱中观察到 λ1 =742 nm主峰 .同时也对多孔硅微腔的 PL 谱和单层多孔硅的光电流谱进行了测量 ,结合有效折射率方法和菲涅耳公式 ,对照 PL 谱和单层多孔硅的光电流谱 ,对常温下多孔硅微腔的光电流谱进行解释 .     

自填隙原子对Si晶体性能影响的研究

运用第一性原理的超软赝势方法研究了Si晶体中自填隙形成的多种缺陷对体Si电子结构和光学性质的影响.理论计算表明,缺陷使体 Si 材料的晶格常数、体积、电学和光学性质等产生了不同程度的改变,空位缺陷导致Si晶体材料吸收光谱红移.     

纳米硅量子点的自然形成及其发光特性

用 Si H4 气体的减压 CVD法 ,在氧化硅以及石英基板上自然形成了高密度的 (～ 10 11cm-2 )纳米尺寸的半球状硅晶粒 (硅量子点 ) ,并且对其光学吸收和发光 (Photo- luminescence,PL)特性进行了评价。用表面热氧化了的硅量子点样品 ,在室温条件且在高于 1.2 e V以上的能量范围内观察到了 PL谱。随着量子点尺寸的减少 ,PL谱的光学吸收限移向高能方向。 PL谱的峰值能呈现大幅度的 (约 0 .9e V)斯塔克移动 ,并且 PL谱的强度几乎与温度无关 ,说明发光来自与局域能级相关联的发光和复合过程。     

微斑光电流谱和光反射谱的自动测量系统

叙述了为测量半导体光电器件的光电流谱和光反射谱所构成的自动测量系统及其数据处理方法。     

Development of highly conducting n-type micro-crystalline silicon oxide thin film and its application in high efficiency amorphous silicon solar cell

Wide band gap and highly conducting n-type nano-crystalline silicon film can have multiple roles in thin film solar cell. We prepared phosphorus doped micro-crystalline silicon oxide films (n-μc-SiO:H) of varying crystalline volume fraction (X_c) and applied some of the selected films in device fabrication, so that it plays the roles of n-layer and back reflector in p-i-n type solar cells. It is generally understood that a higher hydrogen dilution is needed to prepare micro-crystalline silicon, but in case of the n-μc-SiO:H an optimized hydrogen dilution was found suitable for higher X_c. Observed X_c of these films mostly decreased with increased plasma power (for pressure<2.0 Torr), increased gas pressure, flow rate of oxygen source gas and flow rates of PH₃>0.08 sccm. In order to determine deposition conditions for optimized opto-electronic and structural characteristics of the n-μc-SiO:H film, the gas flow rates, plasma power, deposition pressure and substrate temperature were varied. In these films, the X_c, dark conductivity (σ_d) and activation energy (E_a) remained within the range of 0–50%, 3.5×10⁻¹⁰ S/cm to 9.1 S/cm and 0.71 eV to 0.02 eV, respectively. Low power (30 W) and optimized flow rates of H₂ (500 sccm), CO₂ (5 sccm), PH₃ (0.08 sccm) showed the best properties of the n-μc-SiO:H layers and an improved performance of a solar cell. The photovoltaic parameters of one of the cells were as follows, open circuit voltage (V_oc), short circuit current density (J_sc), fill-factor (FF), and photovoltaic conversion efficiency (η) were 950 mV, 15 mA/cm², 64.5% and 9.2% respectively.     

Lithium doping of amorphous silicon

Interstitial doping of glow discharge a-Si with lithium leads to conductivity values comparable to phosphorus doping and offers the advantage that it is applied after the preparation of the films. Results of thermopower and conductivity measurements of an amorphous silicon film doped stepwise by Li implantation are presented. Analysis of the data indicates that the electronic transport is governed by a considerable nonlinear statistical shift of the Fermi level and an activated carrier mobility. From the position of E_F at zero temperature, determined by extrapolation, the density of localized states is inferred. Good agreement is found with published results from field effect measurements.     

Local density of states in photonic crystal cavity

Local radiative density of optical states (LDOS) offers a tool to control the radiative rate of spontaneous emission from molecules,atoms,and quantum dots,which is proportional to LDOS.This paper prese...     

非晶硅碳（a-SiC∶H）薄膜光学常数的透射谱表征

报道了一种用透射谱数据分析法计算非晶硅碳薄膜的厚度、折射率、吸收系数和光学带隙等光学常数的方法和程序．这一方法引用有效谐振子模型理论的折射率色散关系,所有公式均为解析表达式,便于进行数据处理,无须专用软件,使用Excel即可完成,适用于多种半导体薄膜材料．将这种方法应用于PECVD方法制备的非晶硅碳（a-SiC∶H）薄膜,对其光学特性进行了分析．     

太赫兹场作用下半导体超晶格的动力学过程及光吸收谱研究

基于激子基,采用密度矩阵理论研究了太赫兹场作用下半导体超晶格的子带间动力学过程及光吸收谱。在太赫兹场的驱动下,激子作布洛赫振荡。子带间极化的缓慢变化依赖于太赫兹频率,随着太赫兹频率的增加,子带间极化向下振荡,极化强度降低。以 和 两种超晶格为例进行研究,它们的光吸收谱出现了卫星峰结构,这是由于太赫兹场与万尼尔斯塔克阶梯激子作用的非线性效应产生的。但是就 与 超晶格相比而言,我们研究发现,n<0的激子态与n=0的激子态耦合作用较强使得光吸收谱吻合性较好,n＝0时的激子态吸收光谱出现红移,n>0的激子态光吸收谱中出现的边带效应不是很明显。     

光谱吸收光纤气体传感技术探讨

简述了光纤气体传感器的基本特性.介绍了几种光谱吸收光纤气体传感的方法.详细阐述了各种传感原理.分析了影响光谱吸收光纤气体传感精度的因素.     

Comparisons using optoelectronic modulation spectroscopy of n-type GaAs epitaxial layers formed on buffer layers prepared at normal and low temperatures

Optoelectronic modulation spectroscopy (OEMS) has been used to examine defect-related states in GaAs metal-semiconductor, field-effect transistor (MESFET) structures prepared by molecular-beam epitaxy (MBE) on buffer layers formed at normal and low temperatures. The technique was used to simultaneously observe the spectra of defect states near to the interface with the buffer layer and in the active layer. There were few responses that were common to the structures. The most prominent was an electron trap with a depth of 0.92 eV. This was present throughout both structures and may be from a native defect in GaAs. With few exceptions the states seen in a particular structure were present in the active layer as well as near to the interface with the buffer layer suggesting that, in each case, the defects originated from the active/buffer layer interface or from the buffer layer. The most significant difference was that states in the low-temperature (LT)-based structure generally exhibited replicating responses with specific energy periodicities. A model describes this in terms of optical-absorption transitions to the local vibrational states of defects. Five different replica series were observed. The vibrational characteristics of the defects found in the LT material suggest that they are different in character and extent to those defects found in material formed on a normally prepared buffer layer. Their Frank-Condon energies ranged from 9–332 meV.     

La/N共掺Ba5Nb4O15的光电性能的第一性原理研究

采用密度泛函理论（DFT）第一性原理方法研究了La/N共掺对二维钙钛矿Ba5Nb4O15的电子结构、光吸收系数和迁移率的调制作用。计算结果表明,在所选择的掺杂浓度下,La/N共掺使其带隙减小了1.46eV,且仍保持直接带隙,价带顶和导带底都在Γ点。同时,由于掺杂后引入杂质能级使带隙减小,吸收光谱出现明显的红移,可见光区域的光吸收系数显著增大,可有效提高对太阳光的利用率。另外,掺杂后电子和空穴的有效质量显著减小,迁移率提高3～5倍,进一步增强了材料的光电与光催化性能。     

Solution growth of Indium-Doped silicon

Indium-doped silicon has been grown from indium-rich solutions using a gradient-transport solution growth process. The growth temperatures were varied from 950‡ to 1300‡C to determine the solubility limits of indium in silicon. The maximum indium concentration obtained was 1.6×10¹⁸/cm³ at a growth temperature of 1300‡ but indications are that the maximum solubility is 2. 5×10¹⁸/cm³. The growth process is described by one-dimensional diffusion limited transport and predicts growth rates in excess of lcm/day at 1300‡C. Infrared absorption measurements were used to monitor the indium, oxygen and carbon concentrations, in addition to the shallower .indium: X defect found in the crystals. The solution-grown crystals were found to have a lower concentration of this shallower defect than melt grown crystals of the same indium concentration. The oxygen and carbon concentrations increased with the increased growth temperatures suggesting a solubility limited value. The shallower indium: X defect also increased with growth temperature, but the concentration was significantly lower than typically found in melt-grown crystals. The peak optical cross-section for indium was also determined to be 5.3×10^-17cm² from these measurements. This work was sponsored in part by the Defense Advanced Research Projects Agency under Order No. 3211, monitored by NV & EOL under Contract No. DAAK70-77-C-0194.     

Magneto-polaron induced intersubband optical transition in a wide band gap II–VI semiconductor quantum dot

Effects of LO-phonon contribution on the electronic and the optical properties are investigated in a Cd_0.8Zn_0.2Se/ZnSe quantum dot in the presence of magnetic field strength. The magneto-polaron induced hydrogenic binding energy as a function of dot radius in the wide band gap quantum dot is calculated. The oscillator strength and the spontaneous lifetime are studied taking into account the spatial confinement, magnetic field strength and the phonon contribution. Numerical calculations are carried out using variational formulism within the single band effective mass approximation. The optical properties are computed with the compact density matrix method. The magneto-polaron induced optical gain as a function of photon energy is observed. The results show that the optical telecommunication wavelength in the fiber optic communications can be achieved using CdSe/ZnSe semiconductors and it can be tuned with the proper applications of external perturbations.     

非对称量子阱中线性和三阶非线性光吸收系数的研究

主要研究了一个特殊非对称量子阱中的线性和三阶非线性光吸收系数。首先利用量子力学中的密度矩阵算符理论和迭代方法导出了线性和三阶非线性光吸收系数的表达式,然后以典型的非对称量子阱GaAs／AIGaAs材料为例作了数值计算。数值结果表明,入射光强以及系统的非对称性对总的光吸收系数有比较大的影响,从而为实验研究提供理论依据。