Growth of ribbon-shaped crystals of gadolinium gallium garnet for bubble memory substrates

In preliminary work to adapt the edge-defined, film-fed growth (EFG) process to GGG, a number of 1 cm wide × 0.5 mm thick ribbon crystals were obtained. Most of the crystals contained longitudinal thermal stress patterns and associated dislocation arrays. Also evident were occasional arrays of microvoids just under the external surface. In one case where the thermal stresses were avoided, the crystal quality appeared to be sufficient for use in magnetic bubble devices. Off-stoichiometric inclusions on the gallia-rich side were eutectic structures of gallia and garnet and on the gadolinia-rich side were an unidentified gadolinium-rich compound. Lattice parameter measurements of the EFG crystals show that the effective distribution coefficients are much higher than those for the Czochralski growth method. B. Siegel is now with Man Labs., Cambridge, Mass., and H. Lingertat is now with GTE Laboratory, Waltham, Mass.     

Growth and Characterisation of InAsSb Ternary Layers on (101) GaSb Substrates by LP-MOCVD

采用自制的低压金属有机化学气相淀积设备,用三甲基镓、三甲基铟作为III族源,三甲基锑和砷烷作为V族源在(100)面GaSb和GaAs单晶衬底上分别外延生长了InAsSb材料. 用X射线双晶衍射、原子力显微镜、扫描电镜和电子探针能谱仪等对材料特性进行了表征,研究了生长温度、V/III比、过渡层等生长参数对外延层质量的影响. 获得了与GaSb衬底晶格失配度为0.4%的表面光亮且晶体质量较好的InAs0.85Sb0.15外延层.     

Surface treatment of GaSb substrate and extremely low temperature LPE growth of AlGaSb

After each process of a chemical etching, heat-cleaning, melt-back, or soaking in HC1, the substrate surface of GaSb was characterized by the Auger electron spectroscopy with a simultaneous Ar sputtering to reveal oxide layer structures. An optimum treatment process of GaSb surfaces for low temperature LPE growth of AlGaSb was established. Uniform growth of epitaxial AlGaSb on GaSb is demonstrated for a wide temperature range(from 500‡C to as low as 250‡C).     

Growth and characterization of CuSbS2 crystals

The liquidus curves in the Cu-Sb-S system near CuSbS₂ composition and between CuSbS₂ and Sb₂S₃ were determined by cooling arrests of seeded melts. CuSbS₂ melts congruently at 552.25 ± 0.14°C and a eutectic occurs between CuSbS₂ and Sb₂S₃ at 490 ± 5°C and 0.72 ± 0.05 mole fraction Sb₂S₃. No additional phases appear on the liquidus surface in this portion of the Cu-Sb-S system. Crystals of CuSbS₂ were grown from the stoichiometric composition using the Bridgman Stockbarger method. At room temperature, the band gap of CuSbS₂ is 0.28 eV; however below 80K, a drop in resistivity suggests the appearance of a new phase. Measurements of photo current suggest that the band gap of the low temperature phase is greater than 0.58 eV.     

Growth and characterization of undoped and N-type (Te) doped MOVPE grown gallium antimonide

The growth of GaSb by MOVPE and itsn-type doping using a dimethyltellurium dopant source are investigated. The results of growth rate, morphology and Te incorporation as a function of growth parameters are given. Increasing growth temperature and V/III reactant ratio were found to reduce the Te incorporation. The lowest Hall carrier concentrations obtained at room-temperature, onp-type andn-type MOVPE GaSb are respectively:p _H= 2.2 × 10¹⁶cm⁻³ with a Hall mobility ofμ _H= 860 cm²/V.s andn _H= 8.5 × 10¹⁵cm⁻³ withμ _H= 3860 cm²/V.s. Furthermore, Hall mobilities as high as 5000 cm²/V.s were measured onn-type GaSb samples.     

Preparation and properties of pbs crystals with low carrier concentrations

By using a two-temperature annealing technique to reduce native defect concentrations we have achieved carrier concentrations as low as 5. 6 x l0¹⁵ cm^-3 in bulk single crystals of PbS. Hall coef-ficient, electrical resistivity, thermoelectric power, infrared absorption coefficient, and CO₂ laser transmission scan measure-ments were carried out for various samples in the carrier con-centration range from 5. 6 x l0¹⁵ cm^-3 to 4. 8 x 10¹⁸ cm^-3. The low-temperature carrier concentration data were analyzed using a quantitative theory for the native defect concentrations as a function of the sulfur vapor pressure. Calculations based on this theory yield good agreement with experiment for intrinsic carrier concentration and defect equilibrium coefficient values of 5.5 x 10¹⁷ cm^-3 and 5. 0 x 10¹⁷ cm^-3, respectively, at 600°C. This work was sponsored by the Department of the Air Force.     

Influence of alloy composition,substrate temperature,and doping concentration on electrical properties of Si-doped n-Alx Ga1−x As grown by molecular beam epitaxy

Capacitance and Hall effect measurements in the temperature range 10-300 K were performed to evaluate the deep and shallow level characteristics of Si-doped n-Al_xGa_-xAs layers with 0 × 0.4 grown by molecular beam epitaxy. For alloy compositions × 0.3 the overall trap concentration was found to be less than 10⁻² of the carrier concentration. In this composition range the transport properties of the ternary alloy are comparable to those of n-GaAs:Si except for lower electron mobibities due to alloy scattering. With higher Al content one dominant electron trap determines the overall electrical properties of the material, and in n-Al_0.35Ga_0.65As:Si the deep trap concentration is already of the order of the free-carrier concentration or even higher. For the composition × = 0.35 ± 0.02 the influence of growth temperature and of Si dopant flux intensity on the deep trap concentration, on shallow and deep level activation energy, and on carrier freeze-out behaviour was studied and analyzed in detail. Our admittance measurements clearly revealed that the previously assumed deepening of the shallow level in n-Al_x Ga_1-x As of alloy composition close to the direct-indirect cross-over point does actuallynot exist. In this composition range an increase of the Si dopant flux leads to a reduction of the thermal activation energy for electron emission from shallow levels due to a lowering of the emission barrier by the electric field of the impurities. The increasing doping flux also enhances the concentration of the dominant electron trap strongly, thus indicating a participation of the dopant atoms in the formation of deep donor-type (D,X) centers. These results are in excellent agreement with the model first proposed by Lang et al. for interpretation of deep electron traps in n-Al_x Ga_1-x grown by liquid phase epitaxy.     

Growth and characterization of Tl3InSe4 single crystals

Tl₃InSe₄ single crystal has been successfully prepared by the Bridgman crystal growth technique. The crystal that is reported for the first time is found to be of tetragonal structure with lattice parameters of a=0.8035 and c=0.6883 nm. The electrical resistivity and Hall effect measurements on the crystal revealed a conductivity type conversion from p- to n-type at a critical temperature of 283 K. The electron to hole mobility ratio is found to be 1.10. The analysis of the temperature-dependent electrical resistivity, Hall coefficient and carrier concentration data reveals the extrinsic type of conduction with donor impurity levels that behave as acceptor levels when are empty. The data analysis allowed the calculation of the hole and the electron effective masses as 0.654m₀ and 0.119m₀, respectively. In addition, the temperature-dependent Hall mobility in the n-region is found to be limited by the electron–phonon short-range interactions scattering with an electron–phonon coupling constant of 0.21.     

Synthesis,growth and characterization of AgInSe2 single crystals

Single crystal of the ternary semi-conductor AgInSe₂ has been grown by Bridgman technique. The AgInSe₂ crystal crystallizes in the tetragonal chalcopyrite structure. Using melt temperature oscillation method polycrystalline charge was synthesized. The synthesized charge was subjected to powder X-ray diffraction analysis. Thermal property of AgInSe₂ was analyzed using differential scanning calorimetry (DSC) technique. The melting and solidification temperature is 777 °C and 761 °C respectively. The synthesized polycrystalline charge was employed to grow AgInSe₂ single crystals. The grown crystal was confirmed by single crystal X-ray diffraction. The crystal exhibits 60% transmission in the Infrared region. The stoichiometric composition of AgInSe₂ was confirmed by Energy dispersive X-ray analysis (EDAX). The electrical properties of the crystal were studied by Hall Effect measurements and photoconductivity.     

An analytical evaluation of GaAs grown with commercial and repurified trimethylgallium

An analytical study of the impurities in trimethylgallium (TMGa) and subsequent correlation of the effect of these impurities on resulting GaAs films grown by metalorganic chemical vapor deposition (MOCVD) is presented. The effects of using fractional distillation techniques to improve the quality of TMGa and to help isolate and identify major source impurities in TMGa is detailed. Photothermal ionization data are presented which show the residual donor species present and their relative concentrations in the epitaxial layers. Correlations of the residual donor concentrations with TMGa preparation are made. It is demonstrated that high purity GaAs with μ₇₇ K ≈ 125,000 cm²/V-sec can be grown by MOCVD using repurified trimethylgallium and arsine source materials. Work supported in part by the U.S. Naval Research Laboratory on Contract No. N00173-80-C-0066.     

高掺杂浓度Yb∶YAG晶体的生长及光谱性能

应用中频感应提拉法生长了掺杂浓度高达 5 0at. %的Yb∶YAG晶体 ,研究了室温下Yb∶YAG晶体的吸收和发射光谱特性以及荧光寿命 ,在 939nm和 96 9nm处存在Yb3 + 离子的 2个吸收带 ,能与InGaAs激光二极管(LD)有效耦合 ,适合激光管二极抽运。其荧光主峰位于 10 32nm附近 ,Yb∶YAG晶体的荧光寿命为 390 μs。比较了高掺杂与低掺杂Yb∶YAG晶体的光谱参数 ,指出高掺杂Yb∶YAG晶体是一种很有前景的高功率激光增益介质     

弛豫铁电单晶PZNT91/9的生长与畴结构研究

采用熔剂-坩埚下降法生长了91%Pb(Zn1/3Nb2/3)O3-9%PbTiO3(PZNT91/9)(摩尔分数)弛豫铁电单晶,PbO助熔剂摩尔分数控制在50%左右。所得晶体被PbO助熔剂包裹,将其浸泡在热HNO3中1～2天即可除去PbO。晶体呈浅黄色,具有明显的结晶学生长面。晶体沿(001)面切出数片,晶片质量明显好于通气Bridgman法生长的PZNT单晶。偏光显微镜可观察到71°、90°、180°畴或微畴区。晶片极化条件为:垂直于C面施加1kV/mm的电场并保持10～15min。     

高质量镁铝尖晶石单晶生长的研究

对制作微波延迟线用镁铝尖晶石单晶生长进行了研究，采用原料配比为ＭｇＯ：Ａｌ２Ｏ３＝１：１（ｍｏｌ），通过化学反应间接合成ＭｇＡｌ２Ｏ４多晶料，使用铱坩埚盛料，选用中频感应加热，在氩气中用提拉法以及合适的温场和最佳工艺参数，生长了出了高质量的镁铝尖晶石单晶，其性能达到微波器件使用要求。     

大尺寸Bi_（12）S_iO_（20）单晶生长的研究

本文介绍了ＢＳＯ单晶的若干主要性能。报导了用电阻加热提拉法，从φ８０×６０ｍｍ铂金坩埚中生长出φ４０×６０ｍｍ重达８００克左右的优质ＢＳＯ大单晶。研究并确定了生长大尺寸ＢＳＯ晶体的工艺条件，并对晶体中若干主要缺陷进行了观察分析，讨论了它们与生长工艺条件的关系，以及提高晶体质量的主要途经。     

Mg_2SiO_4:Cr~(3+)晶体的生长及其特性

介绍了用提拉法生长的Mg_2SiO_4:Cr~(3+)单晶的生长、结构和形态特征,测定了该晶体的吸收谱和荧光谱。荧光谱电子振动边带在800～1400nm,吸收谱中有一定的Fe~(3+)吸收。     

T46X型硒镓银单晶炉的研制

介绍了TDR-46X型单晶炉的设计思路及工作原理,结合拉制单晶的特殊工艺要求,分析了其主要结构及特点。     

低损耗近零超平坦色散光子晶体光纤的设计

设计了一种用于买现低损耗、近零超平坦色散特性的光子晶体光纤结构,这种结构光纤包层空气孔层数少,内三层空气孔直径相同,制作过程简单;应用多极法研究了此结构PCF各个参数特别是最外层空气孔直径对色散和损耗特性的影响,通过优化结构,设计出了在1.3μm至1.65μm波长范围内色散绝对值小于0.5ps/（nm.km）,1.55μm处损耗为4.5dB/km的低损耗近零超平坦色散光子晶体光纤。     

复合单晶被动调Q光纤激光器的制备与数值模拟

为了开发新型激光材料,采用激光加热基座法将Cr4 ∶YAG单晶光纤和Nd3 ∶YAG单晶光纤生长为一体化复合单晶光纤。利用速率方程理论,得到包含激光增益介质反转密度、光子密度和饱和吸收介质基态布居数密度的速率方程组。通过数值计算,求得复合单晶Cr4 被动调Q光纤激光器的若干重要特征参量及其与抽运率的函数关系曲线,计算结果较好地符合了实验结果,从而可以为优化设计这类单晶光纤激光器提供指导。