Electrical and optical property of annealed Te-doped GaSb

GaSb is the most suitable substrate in the epitaxial growth of mixed semiconductors of GaSb system. In this work, Te-doped GaSb bulk crystals with different doping concentration have been annealed at 550 ℃ for 100 h in ambient antimony. The annealed samples have been studied by Hall effect measurement, infrared (IR) optical transmission, Glow discharge mass spectroscopy (GDMS) and photoluminescence (PL) spectroscopy. After annealing, Te-doped GaSb samples exhibit a decrease of carrier concentration and increase of mobility, along with an improvement of below gap IR transmission. Native acceptor related electrical compensation analysis suggests a formation of donor defect with deeper energy level. The mechanism of the variation of the defect and its influence on the material properties are discussed.     

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.     

碲锌镉晶体生长炉自主设计与控温性能实验

针对直径4英寸碲锌镉单晶材料生长的需求,在研究国外碲锌镉晶体材料生长取得的成果基础上,自主设计了一种基于移动炉体技术的碲锌镉晶体生长炉.炉体由4种规格的六段温控加热单元组成,采用工控机控制伺服电机来驱动滚珠丝杆直线导轨实现炉体升降,炉体内腔设置有刚玉陶瓷管及高温金属热管组成的加热炉管,通过高精度铂铑铂热电偶、欧陆、变压...     

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.     

GaSb衬底上InAsxSb1-x合金的低压MOCVD生长和表征

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.     

设计低对称性全电介质椭圆格点能谷光子晶体

二维拓扑光子绝缘体中格点的对称性作为一个设计的自由度还未被探索.在此研究中通过使用对称性较低的椭圆形格点来研究格点对称性对于能谷光子禁带的影响.通过改变椭圆形格点的长轴方向能够改变能谷光子禁带的中心波长及宽度,并将具有不同禁带宽度及中心波长的全电介质能谷光子晶体结构以镜面对称的方式组合实现全电介质光子拓扑绝缘体波导结构...     

水浴法制备形貌可控的一维ZnO纳米和微米棒

用一步或两步简单的化学溶液法,以醋酸锌为原料,六亚甲基四胺或三乙醇胺为催化剂在玻璃衬底上生长出不同形貌的纳米和微米ZnO棒.探讨了反应液的酸碱度和反应液浓度对生成的ZnO棒形貌的影响,并分析了其生长机制.随着溶液浓度的增加,棒的长度与直径比减小,同时玻璃衬底上生长的ZnO棒从无序分布趋于垂直于衬底平行取向分布.随着pH值的改变,棒的形状由在弱酸性溶液中的细长棒状变为在弱碱性溶液中的圆头对称短棒;当碱性增大到一定程度时,可以生成颗粒状.通过控制一定的酸碱度和溶液浓度,可以得到规则的六角ZnO棒状阵列.测量了样品的XRD和扫描电镜像,并对其发光性能进行了测量分析.其中规则有序六角棒的发光光谱表明峰值在530nm,半高宽为220nm,可能是Vo 的电子和价带中的空穴辐射复合所致.     

水浴法制备形貌可控的一维ZnO纳米和微米棒

用一步或两步简单的化学溶液法,以醋酸锌为原料,六亚甲基四胺或三乙醇胺为催化剂在玻璃衬底上生长出不同形貌的纳米和微米ZnO棒.探讨了反应液的酸碱度和反应液浓度对生成的ZnO棒形貌的影响,并分析了其生长机制.随着溶液浓度的增加,棒的长度与直径比减小,同时玻璃衬底上生长的ZnO棒从无序分布趋于垂直于衬底平行取向分布.随着pH值的改变,棒的形状由在弱酸性溶液中的细长棒状变为在弱碱性溶液中的圆头对称短棒;当碱性增大到一定程度时,可以生成颗粒状.通过控制一定的酸碱度和溶液浓度,可以得到规则的六角ZnO棒状阵列.测量了样品的XRD和扫描电镜像,并对其发光性能进行了测量分析.其中规则有序六角棒的发光光谱表明峰值在530nm,半高宽为220nm,可能是Vo+的电子和价带中的空穴辐射复合所致.     

Structural and electrical characterization of Cu2ZnSnS4 ingot material grown by melting method

In this work,a Cu2ZnSnS4 (CZTS) ingot is grown via a melting method,then cooled;the resulting molten stoichiomet-ric mixture is sealed off in a quartz ampoule under vacuum.The CZTS powder chemical composition analyses are determined us-ing energy dispersive spectroscopy,and revealing the slightly Cu-rich and Zn-poor character of the ingot.Powder X-ray diffrac-tion analysis reveals a crystalline structure with a kesterite phase formation,and a preferred orientation of (112) plane.The lat-tice constants of the a-and c-axes,calculated based on the XRD analyses,are a =5.40 (A) and c =10.84 (A).Based on Hall measure-ments at room temperature,we find that the crystal exhibits p-type conductivity,with a high concentration of 1018 cm-3,a res-istivity of 1.7 Ω cm,and a mobility of 10.69 cm2V-1s-1.Activation energies are estimated based on an Arrhenius plot of conductiv-ity versus 1/T,for a temperature range of 80-350 K,measuring 35 and 160 meV in low-and high-temperature regimes,respect-ively,which is attributed to complex defects (2Cuzn+Snzn) and antisite defects (Cuzn),respectively.The observed scattering mech-anisms are attributed to ionized impurities and acoustic phonons at low and high temperatures,respectively.The extracted band-gap is 1.37 eV.     

SnO2纳米线的低温生长及光致发光研究

在550℃下,通过Au-Ag合金助催热蒸发氧化亚锡,制备了25nm的Sn02纳米线.测试了Sn02纳米线的室温光致发光谱,其四个发光峰中,418nm的峰足新发现的峰,它是孪晶纳米线的面缺陷造成的.SnO2纳米线的低温生长机制遵从VLS生长机制,且与5nO粉末的应用有一定的关系.Sn02纳米线的较小尺度与气相因子的低温度低浓度化学反应有关.     

SnO2纳米线的低温生长及光致发光研究

在550℃下,通过Au-Ag合金助催热蒸发氧化亚锡,制备了25nm的Sn02纳米线.测试了Sn02纳米线的室温光致发光谱,其四个发光峰中,418nm的峰足新发现的峰,它是孪晶纳米线的面缺陷造成的.SnO2纳米线的低温生长机制遵从VLS生长机制,且与5nO粉末的应用有一定的关系.Sn02纳米线的较小尺度与气相因子的低温度低浓度化学反应有关.     

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.     

Nd:CNGG晶体的生长及其性能研究

报道了Nd:CNGG晶体的生长,并对其结构、透过谱以及激光振荡性能进行了研究.利用1W的激光二极管为抽运源,在吸收功率为670mW时获得123.1mW的1.062μm连续激光输出,斜效率达到22.3%.结果表明,Nd:CNGG晶体是一种非常适合激光二极管抽运的固体激光材料.     

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.     

碲硒锌镉单晶体的垂直布里奇曼法生长与性能研究

碲锌镉(CdZnTe)是目前最重要的室温半导体核辐射探测器材料。而在CdZnTe晶格中以Se替位部分Te得到碲硒锌镉(CdZnTeSe),将使得晶格中离子键的成分增加,从而提高晶体的硬度,降低Cd空位和Te夹杂物缺陷浓度,提升材料质量。为了获得适宜于核辐射探测器制备的CdZnTeSe晶体,研究了富Te条件下CdZnTeSe晶体的垂直布里奇曼法生长,成功制备出直径为21 mm、长度超过70 mm的Cd_0.9Zn_0.1Te_0.97Se_0.03单晶锭。所得Cd_0.9Zn_0.1Te_0.97Se_0.03晶体的(110)面X射线衍射摇摆半峰宽达到0.104°,而Te夹杂相的尺寸小于5μm,表明晶体具有良好结晶性。Cd_0.9Zn_0.1Te_0.97Se_0.03晶锭尾部的能带隙和红外透过率均低于晶锭的头部和中部,这可归因于Cd_0.9<...