Photo-assisted metal-organic chemical vapor deposition of CaCu3Ti4O12 (CCTO) thin films

Calcium copper titanate (CaCu₃Ti₄O₁₂) or CCTO is one of the most researched giant dielectric constant materials in recent years. In the present work, incoherent light source based photo-assisted metal-organic chemical vapor deposition (MOCVD) has been used to prepare CCTO thin films on Si/SiO₂ substrates. Key to this unique processing technique is the use of UV radiation as an additional source of energy in conjunction to the thermal energy. The given Photo-assisted MOCVD processing resulted in polycrystalline CCTO growth on a SiO₂ surface. Powder X-ray diffraction and scanning electron microscopy were performed to analyze structural and compositional properties of the CCTO thin film. Ellipsometric measurements indicated a refractive index of 3.03 for the CCTO thin film.     

基于数值模拟的MOCVD反应器设计与优化

介绍了垂直喷淋式MOCVD反应器的最新计算机模拟仿真结果,并根据仿真结果对反应器的结构和参数进行了优化设计,应用在自行研制的用于GaN和四元化合物材料生长的设备中。     

Metalorganic chemical vapor deposition of silver thin films for future interconnects by direct liquid injection system

Deposition of Ag films by direct liquid injection-metal organic chemical vapor deposition (DLI-MOCVD) was chosen because this preparation method allows precise control of precursor flow and prevents early decomposition of the precursor as compared to the bubbler-delivery. Silver(I)-2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedionato-triethylphosphine [Ag(fod)(PEt₃)] as the precursor for Ag CVD was studied, which is liquid at 30 °C. Ag films were grown on different substrates of SiO₂/Si and TiN/Si. Argon and nitrogen/hydrogen carrier gas was used in a cold wall reactor at a pressure of 50–500 Pa with deposition temperature ranging between 220 °C and 350 °C. Ag films deposited on a TiN/Si diffusion barrier layer have favorable properties over films deposited on SiO₂/Si substrate. At lower temperature (220 °C), film growth is essentially reaction-limited on SiO₂ substrate. Significant dependence of the surface morphology on the deposition conditions exists in our experiments. According to XPS analysis pure Ag films are deposited by DLI-MOCVD at 250 °C by using argon as carrier gas.     

Influence of capping layer thickness on the polarization of photoluminescence of CdSe/ZnSe quantum dots grown by metalorganic chemical vapor phase deposition

The polarization of the photoluminescence (PL) of self-assembled CdSe quantum dots (QDs), grown by metalorganic chemical vapor phase deposition, was measured. From the (001) surface, the PL was found preferentially polarized in the direction, while from the cleaved surface in the [001] direction. The polarization of PL depends strongly on the ZnSe capping layer thickness and the PL energy. With an increase in ZnSe coverage, the intensity ratio was found to increase first, then decrease after the coverage is thicker than a critical value. Moreover, such a critical thickness is smaller for larger QDs (lower PL energies). Possible origins of the PL polarization are discussed. We suggest that besides the quantum confinement effects, the strain field in the QDs also plays an essential role in the observed polarization of PL.     

976 nm高效率半导体激光器

976 nm高效率半导体激光器是这几年研究的热点,在固体激光器泵浦领域有广阔的应用。通过优化半导体激光器材料外延结构中包覆层和波导层的铝组分,降低了工作电压;通过采用微通道水冷系统,并进行优化降低了热阻,从而提高了室温下的电光转换效率。25℃室温连续测试条件下,1 cm的线阵列(巴条),2 mm腔长,50%填充因子,在110 A下,出光功率为114.2 W,电压为1.46 V,电光转换效率为71%。15条微通道封装成的垂直叠阵,进行光束整形后,获得了室温976 nm连续输出功率1 500 W,电光转换效率大于70%。     

AlGaAs／AlAs体系DBR的MOCVD生长及表征

设计并利用MOCVD在（311）GaAs衬底上生长了12．5个周期的Al0．6Ga0．4As／AlAs黄绿光分布式Bragg反射（DBR）体系，测量了白光反光谱及其外延片峰值波长分布，反射率90％以上，波长不均匀性在1．0％以下；利用了X射线双晶衍射对其进行结构表征，580nm波长DBR结构周期为84．5nm。     

The growth of InAsSb/InAsP strained-layer superlattices for use in infrared emitters

We describe the metalorganic chemical vapor deposition of InAsSb/InAsP strained-layer superlattice (SLS) active regions for use in mid-infrared emitters. These SLSs were grown at 500°C, and 200 Torr in a horizontal quartz reactor using TMIn, TESb, AsH₃, and PH₃. By changing the layer thickness and composition, we have prepared structures with low temperature (≤20K) photoluminescence wavelengths ranging from 3.2 to 4.4 μm. Excellent performance was observed for a SLS light emitting diode (LED) and both optically pumped and electrically injected SLS lasers. An optically pumped, double heterostructure laser emitted at 3.86 μm with a maximum operating temperature of 240K and a characteristic temperature of 33K. We have also made electrically injected lasers and LEDs utilizing a GaAsSb/InAs semi-metal injection scheme. The semi-metal injected, broadband LED emitted at 4 μm with 80 μW of power at 300K and 200 mA average current. The InAsSb/InAsP SLS injection laser emitted at 3.6 μm at 120K.     

In-situ monitoring and control for MOCVD growth of AlGaAs and InGaAs

We have used spectroscopic ellipsometry to perform real-time monitoring during metalorganic chemical vapor deposition growth of AlGaAs (on GaAs) and InGaAs (on GaAs and InP). Optical constants for these materials were obtained up to growth temperatures of 600 to 700°C. This information permits real-time extraction of composition and layer thickness from the raw ellipsometric data at sample rates on the order of 0.5 Hz. We describe closed-loop control of composition and total layer thickness on AlGaAs-based structures, including Bragg reflectors. In-situ data obtained on double-heterostructure quantum-well laser structures demonstrate that spectroscopic ellipsometry is an extremely powerful monitoring and quality-control tool, giving important real-time information on complex structures that would be difficult and time-consuming to obtain after growth.     

Ultraviolet detectors based on epitaxial ZnO films grown by MOCVD

High-quality zinc oxide (ZnO) films were epitaxially grown on R-plane sapphire substrates by metalorganic chemical vapor deposition at temperatures in the range of 350°C to 600°C. In-situ nitrogen compensation doping was performed using NH₃. Microstructural and optical properties of the films, as well as the N-doping effects, were studied. The metal-semiconductor-metal ultraviolet sensitive photodetectors were fabricated on N-doped epitaxial ZnO films. The detector showed fast photoresponse, with a rise time of 1 μs and a fall time of 1.5 μs. Low-frequency photoresponsivity, on the order of 400 A/W at 5 V bias, was obtained.     

GaAs平面掺杂势垒二极管

二极管是定向检波器的重要组件,提高定向检波器的检波灵敏度,需要降低二极管的开启电压.而平面掺杂势垒(PDB)二极管具有极低的势垒高度,适合制作定向检波器.设计了GaAs平面掺杂势垒二极管的材料结构,并采用金属有机化合物气相淀积(MOCVD)方法对其进行外延生长.对PDB二极管的物理模型进行了理论分析.通过模拟计算和实验分析了本征层厚度和p层的面电荷密度对PDB二极管I-V特性的影响.通过实验设计优化了材料结构参数,测试了其I-V特性,使PDB二极管的开启电压降低到了0.06 V,将此样品应用到定向检波器中测得检波灵敏度为20～ 25 mV/mW.