bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of polyimide sacrificial layers for the manufacturing of uncooled double-cantilever microbolometers
Authors: Huang Shusen , Zhang Xin 
Published: April 2011

ABSTRACTIn this paper, a low-temperature surface micromachining module with two sacrificial layers of polyimide is developed for the manufacturing of double-cantilever microbolometer focal plane arrays. The use of spin-on polyimide allows an all-dry final release step overcoming stiction problems often encountered in wet sacrificial etching processes. For the patterning of the polyimide, a plasma-enhanced chemical vapor deposited silicon oxide is employed as a mask layer. Anisotropic etching of both the mask film and the polyimide layer is accomplished by reactive ion etching. After patterning structural layers, sacrificial etching of the polyimide is conducted using an isotropic dry etch process in high-density oxygen plasma.
Strain compensation effect on stacked InAs self-assembled quantum dots embedded in GaNAs layers
Authors: Oshima Ryuji , Hashimoto Takayuki , Shigekawa Hidemi , Okada Yoshitaka 
Published: April 2011

ABSTRACTWe have studied the effect of strain compensation in multiple stacking of InAs self-assembled quantum dots on GaAs (001) substrates grown by atomic hydrogen assisted RF-molecular beam epitaxy. The GaNxAs1−x material was used as a strain compensating spacer layer. We confirmed by high resolution x-ray diffraction measurements that a 40 nm GaN0.005As0.995 strain compensating layer provides compressive strain to compensate for tensile strain induced by 2.0 ML InAs quantum dots. Consequently, we achieved a multiple stack of InAs QDs up to 30 layers without formation of coalesced QDs, and the density of QDs exceeded 1012 cm−2.
Colloidal quantum dot active layer electroluminescence in a solid GaN matrix
Authors: Pagan Jennifer , Stokes Edward , Patel Kinnari , Burkhart Casey , Ahrens Mike 
Published: April 2011

ABSTRACTIn this paper the preliminary results of incorporating a novel active layer into a GaN light emitting diode (LED) are discussed. Integration of colloidal CdSe quantum dots into a GaN LED active layer is demonstrated. The conductivity of the overgrowth was examined by circular transmission line method (CTLM). Effects on surface roughness due to the active layer incorporation are examined using atomic force microscopy (AFM). LED test devices were fabricated and electroluminescence was demonstrated, the devices exhibit higher turn-on voltages than would be expected for a CdSe active layer.
Material synthesis and infrared optical properties of transition metal doped binary and ternary II-VI semiconductors
Authors: Hömmerich Uwe , Nyein Ei Ei , Trivedi Sudhir B. , Bluiett Althea G. 
Published: April 2011

ABSTRACTWe report on the material preparation and optical characterization of transition metal (Cr, Co) doped ternary cadmium chalcogenides for possible applications in mid-infrared (MIR) light source development. Cr2+ doped II-VI's (e.g. ZnSe, ZnS) have received significant attention for MIR solid-state laser development in the 2-3 μm region. Transition metal (TM) doped II-VI thin films are also currently being studied for the development of broadly tunable MIR sources pumped through electrical carrier-injection. In this paper, we present results of the material synthesis and IR spectroscopy of several Cr and Co doped cadmium chalcogenides including CdTe, CdMnTe, CdZnTe, CdMgTe, CdCaTe, and CdSrTe. Following the synthesis and purification of undoped II-VI materials, TM doping was achieved during in-situ Bridgman growth or through a thermal diffusion process. The Cr2+ doped II-VI materials were characterized by broad IR absorption bands centered at ∼1800–1900 nm and MIR emission extending from ∼2000–3500 nm. The emission lifetimes varied between 1-5 μs, depending on the Cr concentration and host composition. Co2+ doped cadmium chalcogenides exhibited several absorption bands in the infrared region and broad emission extending from ∼3-5 μm. Compared to Cr2+ doped II-VI's, the emission from Co2+ doped chalcogenides was significantly quenched at room-temperature due to the onset of non-radiative relaxations.
Quantum-well Intermixing using Ge-doped Sol-gel Derived Silica Encapsulant Layer
Authors: Djie Hery Susanto , Ooi Boon-Siew , Ho Charles Kin-Fai , Mei Ting , Pita Kantisara , Ngo Quoc-Nam 
Published: April 2011

ABSTRACTWe report the intermixing enhancement using the Ge-doped sol-gel derived silica encapsulant layer in InGaAs/InGaAsP quantum-well laser structure. A bandgap shift of ∼64 nm has been observed from 16% Ge-doped silica capped sample at an annealing temperature of 630°C while the intermixing at the similar temperature can be effectively suppressed with the e-beam evaporated SiO2 encapsulant layer. Using our theoretical model, nearly identical activation energy of 1.7±0.5 eV was obtained from the intermixed sample with Ge-doped silica. Similar intermixing enhancement holds for high Ge-content cap in the intermixed GaAs/AlGaAs quantum-wells related to Ga vacancy injection. We postulate that the dissimilarity in interdiffusion behavior between 0% and 16% Ge-doped silica capped sample is only attributed to the difference in the number of beneficial vacancies that involve in the intermixing process.
Purification, material synthesis, and infrared emission from Nd doped PbBr2 and PbI2
Authors: Hömmerich Uwe , Nyein Ei Ei , Trivedi Sudhir B. , Bluiett Althea B. , Zavada John M. 
Published: April 2011

ABSTRACTWe report on the material synthesis and infrared optical properties of Nd doped lead bromide (PbBr2) and lead iodide (PbI2) bulk crystals. Commercial PbBr2 and PbI2 materials were purified through repeated solidification and horizontal zone refinement. After purification, Nd doped lead halides were synthesized and grown by Bridgman technique. Under optical excitation, Nd:PbBr2 samples exhibited several near-infrared emission bands centered at 816 nm, 891 nm, 963 nm, 1069 nm, 1183 nm, 1356 nm, and 1535 nm. The emission from Nd:PbI2 samples was similar to that of from Nd:PbBr2, but slightly shifted to longer wavelengths. The observation of 1540 nm emission from Nd3+ ions is unusual and reflects on the small non-radiative decay rates in the investigated halides. Lead halides have low maximum phonon energies, which reduces non-radiative decay due to multi-phonon relaxations. In contrast to Nd:YAG, Nd:PbBr2 and Nd:PbI2 exhibited efficient emission from the 4F5/2, 2H9/2 excited states, which are located only ∼1000cm−1 above the 4F3/2 level of Nd3+. Under 808 nm diode pumping, both samples also exhibited broad mid-infrared emission bands centered at ∼5.1 μm.
Optical investigations on sputtered CuCl thin films
Authors: Natarajan Gomathi , Mitra Anirban , O'Reilly Lisa , Daniels Stephen , Cameron David C. , McNally Patrick J. , Lucas Olabanji F. , Bradley Louise 
Published: April 2011

ABSTRACTCopper (I) chloride (CuCl) is a potential candidate for ultra violet optoelectronics due to the fact that it is closely lattice matched with silicon, which makes it readily integrable with silicon device technology. The structural and optoelectronic properties of CuCl thin films deposited by RF magnetron sputtering are investigated. The crystallinity is studied using X-ray diffraction which confirms the growth of CuCl thin films with cubic zinc blende structure predominantly orientated in <111> direction. Excitonic transitions in the thin films were thoroughly investigated using optical absorbance and luminescence spectroscopies. Room temperature absorption spectroscopic analysis confirms the existence of two exciton peaks namely Z12 and Z3 at 372 and 380 nm respectively. A strong UV emission is observed at room temperature in cathodoluminescence and photoluminescence spectra due to the recombination of Z3 exciton at approximately 384 nm. In the low temperature photoluminescence spectrum, a free exciton (Z3) and a bound exciton (I1) are observed. A variation of 1.3 nm to 10 nm was observed in the Z3 exciton line width from 10 K to 300 K.
Fabrication of Nitrided Mask on GaAs surface and Its Machinability for STM lithography
Authors: Yamamoto Yo , MATSUOKA Sota , Kondo Toshiyuki , Maruyama Takahiro , Naritsuka Shigeya 
Published: April 2011

ABSTRACTA nitridation mask on a GaAs surface was prepared using RF-MBE and its machinability by STM lithography was studied. A 5.2 nm thick crystal-like layer was formed at 350°C, and was modified by STM at a sample bias of ±80V with good size reliability, which was sufficiently fine for realizing dislocation-free heteroepitaxial growth of GaAs / Si. The mask was maintained up to 620°C under As flux exposure at 1.5 × 10−4 Pa.
Crystal structure and physical properties of GaSe single crystals annealed in sulfur atmosphere
Authors: Voevodina Olga V. , Morozov Aleksandr N. , Sarkisov Sergey Yu. , Andreev Yuri M. , Fernelius Nils C. , Goldstein Jonathan T. 
Published: April 2011

ABSTRACTIn spite of the progress in GaSe growing technology (high-quality crystals grown by the latest technology are characterized by low values of optical losses with the absorption coefficient values lying below 0.1 cm−1) the work continues on improving crystal properties for nonlinear optical applications. This paper presents the results of investigations on the influence of annealing in a sulfur atmosphere and in a vacuum on the properties GaSe single crystals, grown by the Bridgman method from the melt. The objective of this work was to study the possibility of intercalating GaSe with sulfur from the gas phase, and to compare the influence of doping with sulfur from melt and vapor phase on the structure and properties of GaSe crystals. Three series of annealing experiments have been conducted at temperatures 773, 923, 1073 K and the samples obtained have been studied by Hall effect, photoconductivity, optical absorption, microhardness measurements and X ray diffractometry. The results obtained are explained by assuming the intercalating of sulfur to the interlayer space and substitution of Se with S.
New Solar Cells with Novel Light Trapping via Textured Photonic Crystal Back Reflector
Authors: Zeng Lirong , Yi Yasha , Hong Ching-yin , Alamariu Bernard A. , Liu Jifeng , Duan Xiaoman , Kimerling Lionel C. 
Published: April 2011

ABSTRACTWe have successfully developed a new light-trapping scheme for solar cells that can enhance the optical path length by more than 104 times using a textured photonic crystal structure as a backside reflector. Top-contacted crystalline Si solar cells integrated with the new back reflector were designed, fabricated and characterized. Both external quantum efficiency and power conversion efficiency of the cells have shown significant improvement due to the path length enhancement furnished by the new back reflector despite of the 675 um thick wafers and relatively short minority carrier diffusion length.
Evolution of the optical band gap in Titanium-based Oxy-(Hydroxy)-Fluorides series
Authors: Penin Nicolas , Viadere Nicolas , Dambournet Damien , Tressaud Alain , Demourgues Alain 
Published: April 2011

ABSTRACTThe optical band gap related to the electronic structures as well as the refractive index function of the electronic polarizability of the network can be tailored by changing the nature and the number of anions into the vicinity of cations. New routes have been developed in order to prepare new divided Ti(IV)-based oxyfluorinated compounds. In these compounds, the optical absorptions appear at the UV-Vis frontier and the refractive index is always smaller than the one of equivalent oxides. The chemical bonding, the hybridation and the density of the network play key roles in the variation of the optical band gap and the refractive index. For this family of titanium-based oxyfluorides containing mixed anions, chemical compositions and structural features have been correlated to the optical band gap and the refractive index, i.e. the complex index of materials n(λ) + ik(λ). Several examples will be given in order to illustrate the potentialities of these new inorganic compounds by changing the F/Ti ratio and the cationic substitution.
Heterojunction, Vacuum-Glass Field Effect Transistors
Authors: Geis Michael W. , Deneault Sandra , Krohn Keith E. , Marchant Michael , Cooke David L. , Lyszczarz Theodore M. 
Published: April 2011

ABSTRACTThis note reports on a surface field effect transistor, SFET, where the electron channel consists of the interface between vacuum and a Cs-doped glass, and an electrode on the back of the glass substrate is used as the gate. The device has a transconductance of 4×10−10 S cm−1. The transconductance is limited by the glass surface roughness, ∼ 0.4 nm RMS. A reduction of surface roughness to 0.1 nm RMS is expected to increase device transconductance.
Implantation and Activation of High Concentrations of Boron and Phosphorus in Germanium
Authors: Suh Yong Seok , Carroll Malcolm S. , Levy Roland A. , Bisognin Gabriele , Salvador Davide De , Sahiner M. Alper 
Published: April 2011

ABSTRACTThe effect of increasing boron or phosphorus implant dose (i.e., 5×1013-5×1016 cm−2) and subsequent annealing (400-600°C for 3 hrs in N2) on the activation, diffusion and structure of germanium is studied in this work. The peak concentration of implant dose is ∼ 2×1021 cm−3. Secondary ion mass spectrometry (SIMS), spreading resistance profiling (SRP), high resolution X-ray diffraction (HRXRD), X-ray absorption fine structure (XAFS), Rutherford backscattering spectrometry (RBS), and nuclear reaction analysis (NRA) were used to characterize the implant and activation behavior. Boron is found to have a high solid solubility (i.e., > 2×1020 cm−3), even immediately after implant; while in contrast, phosphorus is limited to ∼ 1–2×1019 cm−3. Diffusion of phosphorus is also extremely extrinsic, while boron is practically immobile.
Silicon Surface Texturization Mechanism by Hydrogen Radicals Using Tungsten Hot Filament
Authors: Nagayoshi Hiroshi , Sato Hiroaki , Nishimura Suzuka , Terashima Kazutaka 
Published: April 2011

ABSTRACTThis paper describes the surface texturing mechanism on crystalline Si using hydrogen radicals generated by a tungsten hot filament. Inverted pyramid or labyrinthV groove structure could be obtained by particle deposition before etching. Mesh like tungsten particle layer, works as an etching mask against hydrogen radical, was obtained when silicon substrate was used. On the other hand, tungstem particles were not deposited as mesh like pattern when SiO2/Si substrate was used. The results suggest that evaporation of silicon hydrides from the silicon surface by hydrogen radical etching causes the mesh like pattern deposition of tungsten particles. Increase of filament current enables short time texturing process of less than 1 minute.
Kinetically controlled superstructural phases at the Sb/Si (5 5 12) interface
Authors: Kumar Mahesh , Paliwal Vinod Kumar , Govind  , Vedeshwar A. G. , Shivaprasad S. M. 
Published: April 2011

ABSTRACTThe adsorption of Sb on the high index Si (5 5 12) has been studied at higher substrate temperature (HT) (800°C), using in situ surface characterization techniques like Auger Electron Spectroscopy (AES), Low Energy Electron Diffraction (LEED), and Electron Energy Loss Spectroscopy (EELS). The surface morphology of this high index Si (5 5 12) surface has row like trenches along (110) direction. We have performed the study of Sb adsorption and desorption on the Si (5 5 12) substrate held at different temperatures. The different pathways adopted during adsorption and desorption have suggested the dominant role of kinetics I forming various surface phases on the Si (5 5 12) substrate. The adsorption at room temperature resulted in the formation of (225) surface phase, while the adsorption at 680°C resulted in the (337) phase. The sequential thermal desorption of the room temperature and high temperature adsorbed surface resulted in the formation of (337) phases at 800°C, with anisotropic growth along one direction. While the adsorption at 800°C resulted in the formation of anisotropic (337) like phases, the further increase in the coverage formed a 2x Si (225) phase. Annealing this 2x Si (225) phase again resulted in the formation of anisotropic (337) phase. Thus formation of interface by controlling the growth kinetics can result in the formation of various tailored structures with desired properties.
ZnO-based p-n Junctions with p-type ZnO by ZnTe Oxidation
Authors: Kaminska Eliana , Przezdziecka Ewa , Piotrowska Anna , Kossut Jacek , Dynowska Elzbieta , Dobrowolski Witold , Barcz Adam , Jakiela Rafal , Lusakowska Elzbieta , Ratajczak Jacek 
Published: April 2011

ABSTRACTThe fabrication and properties of ZnO-based rectifying p-n and p-i-n junctions are reported. ZnO films with p-type conductivity were obtained by oxidation of ZnTe grown by MBE on GaAs substrate. Insulating and n-type ZnO films were deposited by magnetron sputtering. The processing of p-n junctions into device structures involved the formation of mesa geometry and preparation of ohmic contacts to p- and n-type regions.
Group I elements in ZnO
Authors: Meyer Bruno K. , Volbers N. , Zeuner A. , Lautenschläger S. , Sann J. , Hoffmann A. , Haboeck U. 
Published: April 2011

ABSTRACTDiffusion of Li, Na and K into single-crystal substrates of ZnO were performed. We compare the results with ZnO epitaxial films doped with the respective elements during growth. The diffused and in-situ doped layers were studied using mass spectroscopy, low temperature photoluminescence and Raman spectroscopy. Li and Na are known to produce deep acceptor centers which give rise to shallow donor to deep acceptor recombinations in the visible spectral region. We will demonstrate that also shallow acceptors are introduced having binding energies around 300 meV. A donor-acceptor pair recombination (zero phonon line at 3.05 eV) with LO phonon replica is observed analogous to the “edge” emission in other II-VI compounds.
Comparison of Lasing Characteristics of GaInNAs Quantum Dot Lasers and GaInNAs Quantum Well Lasers
Authors: Liu Chongyang Y. , Yoon Soon Fatt , Sun Zhongzhe Z. 
Published: April 2011

ABSTRACTSelf-assembled GaInNAs/GaAsN single layer quantum dot (QD) lasers grown using solid source molecular beam epitaxy have been fabricated and characterized. Temperature-dependent measurements have been carried out on the GaInNAs QD lasers. High-temperature operation up to 65°C was demonstrated from an unbonded GaInNAs QD laser (50 × 1060 μm2), with high characteristic temperature (T0) of 79.4 K in the temperature range of 10-60°C. For comparison, temperature-dependent operation has also been studied on the GaInNAs single quantum well (SQW) lasers. Unlike the relation between the cavity length and T0 in GaInNAs SQW lasers, longer-cavity GaInNAs QD laser (50 × 1700 μm2) showed lower T0 of 65.1 K, which is presumably believed due to the nonuniformity of the GaInNAs QD layer.
Interdiffused SbN-based Quantum Well on GaAs for 1300-1550 nm Diode Lasers
Authors: Arif Ronald A. , Tansu Nelson 
Published: April 2011

ABSTRACTA new method to realize InGaAsSbN quantum well (QW) structures on GaAs substrate is presented. This approach combines the established growth technique of InGaAsN and InGaAsSb QWs by metal organic chemical vapor deposition (MOCVD), with a post-growth thermal interdiffusion to achieve high quality interdiffused InGaAsSbN QW for diode lasers emitting at 1300-1550-nm. In addition to presenting the optimized interdiffused SbN-based QW design at 1550-nm, strain-compensated interdiffused InGaAsSb-GaAsN QW structure is also presented. Preliminary experimental findings of N- and Sb-diffusivities in GaAs matrix show good agreement with theory, indicating the feasibility of realizing interdiffused InGaAsSbN QW.
High-speed high-quality epitaxial growth of N and B codoped 6H-SiC by closed sublimation method
Authors: Maeda Tomohiko , Nakamura Yoshihiro , Iwaya Motoaki , Kamiyama Satoshi , Amano Hiroshi , Akasaki Isamu , Furusho Tomoaki , Kinoshita Hiroyuki , Yoshimoto Masahiro 
Published: April 2011

ABSTRACTN and B codoped 6H-SiC epilayers were grown by the closed sublimation method, the growth rate of which was as high as 100 mm/h. Donor acceptor (DA) pair emission at different temperatures was investigated for two samples with different B concentrations. The integrated photon count obtained from the photoluminescence (PL) spectra of the sample having high B concentration increases with temperature. To estimate the internal quantum efficiency, we measured the PL integrated photon counts of GaN at 10 K as a reference. The integrated PL photon count of 6H-SiC DA-doped epilayer at 250 K is almost comparable to that of GaN at 10 K, which is thought to be almost 100% because of the freezing of the nonradiative recombination at low temperature. This result implies that the internal quantum efficiency of the 6H-SiC DA-doped epilayer exceeds 95%.
Polarity dependence of In-rich InGaN and InN/InGaN MQWs
Authors: Che Songbek , Shinada Takuro , Mizuno Tomoyasu , Ishitani Yoshihiro , Yoshikawa Akihiko 
Published: April 2011

AbstractIn-rich InGaN films (XIn>0.5) and InN/InGaN multi-quantum wells were grown on Ga- and N-polarity GaN templates by radio-frequency plasma-assisted molecular beam epitaxy. The In-polarity InGaN films grown at 450°C showed superior crystalline quality and smoother surface morphology compared to the N-polarity samples, which were grown at 500∼550°C. By using the In-polarity In0.7Ga0.3N as a barrier layer, the InN/InGaN multi-quantum wells were successfully fabricated on the III-element polarity GaN templates at 450°C. Fine periodic structures and strong photoluminescence emission around optical communication wavelength were obtained from the In-polarity MQWs. These results indicate that the In-polarity growth is preferred to obtain a high quality InGaN film and the InN/InGaN MQWs in spite of its lower growth temperature.
Temperature dependence of transport properties of InN films
Authors: Thakur J.S. , Naik R. , Naik Vaman M , Haddad D. , Auner G.W. , Lu H. , Schaff W.J. 
Published: April 2011

AbstractThe temperature dependence of Hall mobility, µ, and carrier density, Ne, for thin InN films grown by Molecular Beam Epitaxy and Plasma Source Molecular Beam Epitaxy have been investigated. For temperature up to 300 K, a large temperature-independent Ne is observed in films grown by the above two techniques. However, for higher temperatures, carrier density (Ne) increases with temperature. The characteristic behavior of the mobility for the films with low carrier density is different from that of the high carrier density film, particularly at low temperatures. The low carrier density film shows a peak ∼250 K in mobility as a function of temperature which is contrast to the temperature independent mobility observed for the high density film for T < 300 K. We have investigated theoretically the effect of concentration of donor, acceptor, and threading dislocations on the carrier mobility in these films. Various electron-scattering mechanisms for the mobility in these films have been discussed.
The mean inner potential of GaN measured from nanowires using off-axis electron holography
Authors: Wong Andrew See Weng , Ho Ghim Wei , Dunin-Borkowski Rafal E , Kasama Takeshi , Oliver Rachel A , Costa Pedro MFJ , Humphreys Colin John 
Published: April 2011

AbstractThe mean inner potentials of wurtzite GaN nanowires are measured using off-axis electron holography in the transmission electron microscope (TEM). The nanowires have a circular cross-section and are suspended across holes in a holey carbon film, resulting in an accurate knowledge of their thickness profiles and orientations. They are also free of the implantation and damage that is present in mechanically-polished ion-milled TEM specimens. The effect of a thin amorphous coating, which is present on the surfaces of the nanowires, on measurements of their mean inner potential is assessed. A value for the mean inner potential of GaN of (16.7 ± 0.3) V is obtained from these samples.