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Growth of AlGaSb Compound Semiconductors on GaAs Substrate by Metalorganic Chemical Vapour Deposition  [PDF]
A. H. Ramelan,H. Harjana,P. Arifin
Advances in Materials Science and Engineering , 2010, DOI: 10.1155/2010/923409
Abstract: Epitaxial Sb layers on GaAs substrate have been grown by atmospheric pressure metalorganic chemical vapour deposition using TMAl, TMGa, and TMSb. We report the effect of V/III flux ratio and growth temperature on growth rate, surface morphology, electrical properties, and composition analysis. A growth rate activation energy of 0.73?eV was found. For layers grown on GaAs at 580°C and 600°C with a V/III ratio of 3 a high quality surface morphology is typical, with a mirror-like surface and good composition control. It was found that a suitable growth temperature and V/III flux ratio was beneficial for producing good AlGaSb layers. Undoped AlGaSb grown at 580°C with a V/III flux ratio of 3 at the rate of 3.5? m/hour shows p-type conductivity with smooth surface morphology and its hole mobility and carrier concentration are equal to 237? /V.s and 4.6?×? ? , respectively, at 77?K. The net hole concentration of unintentionally doped AlGaSb was found to be significantly decreased with the increased of aluminium concentration. All samples investigated show oxide layers ( , , and ) on their surfaces. In particular the percentage of aluminium-oxide was very high compared with a small percentage of AlSb. Carbon content on the surface was also very high. 1. Introduction Because of the corresponding wavelengths of the alloys of gallium antimonide- (GaSb-) based compound semiconductors cover a wide spectral range from 1.24? m (AlGaSb or AlGaAsSb) to 4.3? m (InGaAsSb), they have received increasing attention recently. Consequently, they became promising candidates for applications in long wavelength lasers and photodetectors for fibre optic communication systems [1–3]. It is ideal to grow the AlGaSb films on lattice-matched GaSb substrates. However, due to the lack of semi-insulating GaSb, undoped substrates have a strong free carrier absorption in the mid-IR wavelength region of interest, so that the substrate must be thinned for optimal device operation in the flip-chip mode. For this and commercial reasons, GaAs has been explored as a substrate for GaSb/AlGaSb devices. Unfortunately, a lattice mismatch of approximately 7% exists between GaSb and GaAs. Strain energy can be accommodated by misfit dislocations at the GaAs/GaSb interface. This results in the propagation of threading dislocations through the epilayers [4]. Thus, the growth of undoped high-quality GaSb/AlGaSb layers on GaAs substrate becomes a necessary process for preparing thin layers. These films have usually been grown by liquid phase epitaxy or molecular beam epitaxy (MBE) with relatively little
Exploration of oxide-based diluted magnetic semiconductors toward transparent spintronics  [PDF]
T. Fukumura,Y. Yamada,H. Toyosaki,T. Hasegawa,H. Koinuma,M. Kawasaki
Physics , 2003, DOI: 10.1016/S0169-4332(03)00898-5
Abstract: A review is given for the recent progress of research in the field of oxide-based diluted magnetic semiconductor (DMS), which was triggered by combinatorial discovery of transparent ferromagnet. The possible advantages of oxide semiconductor as a host of DMS are described in comparison with conventional compound semiconductors. Limits and problems for identifying novel ferromagnetic DMS are described in view of recent reports in this field. Several characterization techniques are proposed in order to eliminate unidentified ferromagnetism of oxide-based DMS (UFO). Perspectives and possible devices are also given.
Recent Progress in III-V based ferromagnetic semiconductors: Band structure, Fermi level, and tunneling transport  [PDF]
Masaaki Tanaka,Shinobu Ohya,Pham Nam Hai
Physics , 2013, DOI: 10.1063/1.484013
Abstract: Spin-based electronics or spintronics is an emerging field, in which we try to utilize spin degrees of freedom as well as charge transport in materials and devices. While metal-based spin-devices, such as magnetic-field sensors and magnetoresistive random access memory using giant magnetoresistance and tunneling magnetoresistance, are already put to practical use, semiconductor-based spintronics has greater potential for expansion because of good compatibility with existing semiconductor technology. Many semiconductor-based spintronics devices with useful functionalities have been proposed and explored so far. To realize those devices and functionalities, we definitely need appropriate materials which have both the properties of semiconductors and ferromagnets. Ferromagnetic semiconductors (FMS), which are alloy semiconductors containing magnetic atoms such as Mn and Fe, are one of the most promising classes of materials for this purpose, and thus have been intensively studied for the past two decades. Here, we review the recent progress in the studies of the most prototypical III-V based FMS, p-type (GaMn)As, and its heterostructures with focus on tunneling transport, Fermi level, and bandstructure. Furthermore, we cover the properties of a new n-type FMS, (InFe)As, which shows electron-induced ferromagnetism. These FMS materials having zinc-blende crystal structure show excellent compatibility with well-developed III-V heterostructures and devices.
Macroporous Semiconductors  [PDF]
Helmut F?ll,Malte Leisner,Ala Cojocaru,Jürgen Carstensen
Materials , 2010, DOI: 10.3390/ma3053006
Abstract: Pores in single crystalline semiconductors come in many forms (e.g., pore sizes from 2 nm to > 10 μm; morphologies from perfect pore crystal to fractal) and exhibit many unique properties directly or as nanocompounds if the pores are filled. The various kinds of pores obtained in semiconductors like Ge, Si, III-V, and II-VI compound semiconductors are systematically reviewed, emphasizing macropores. Essentials of pore formation mechanisms will be discussed, focusing on differences and some open questions but in particular on common properties. Possible applications of porous semiconductors, including for example high explosives, high efficiency electrodes for Li ion batteries, drug delivery systems, solar cells, thermoelectric elements and many novel electronic, optical or sensor devices, will be introduced and discussed.
Recent Progress in the Magnetism Theory of ZnO-based Diluted Magnetic Semiconductors  [PDF]
LIU Xue-Chao,CHEN Zhi-Zhan,SHI Er-Wei,SONG Li-Xin
无机材料学报 , 2009, DOI: 10.3724/sp.j.1077.2009.00001
Abstract: Diluted magnetic semiconductors (DMSs) are new functional materials formed by doping a few percentages of magnetic ions in nonmagnetic semiconductors. Recently, the ferromagnetism origin and magnetism theory are the research hotspot in the field of DMSs. It is still unclear how the ferromagnetism is induced between the doped magnetic ions and the carriers. In this paper, the recent progress in magnetism theory was reviewed. The typical theories including RKKY, mean field theory, double exchange and bound magnetic polaron were elucidated in detail. The hotspot of experimental, theoretical research and existing problems were evaluated.
Application of Nanostructures in Electrochromic Materials and Devices: Recent Progress  [PDF]
Jin Min Wang,Xiao Wei Sun,Zhihui Jiao
Materials , 2010, DOI: 10.3390/ma3125029
Abstract: The recent progress in application of nanostructures in electrochromic materials and devices is reviewed. ZnO nanowire array modified by viologen and WO 3, crystalline WO 3 nanoparticles and nanorods, mesoporous WO 3 and TiO 2, poly(3,4-ethylenedioxythiophene) nanotubes, Prussian blue nanoinks and nanostructures in switchable mirrors are reviewed. The electrochromic properties were significantly enhanced by applying nanostructures, resulting in faster switching responses, higher stability and higher optical contrast. A perspective on the development trends in electrochromic materials and devices is also?proposed.
Gold contacts to semiconductor devices
James W. Mayer
Gold Bulletin , 1984, DOI: 10.1007/BF03214672
Abstract: The electronics revolution led by computers and microprocessors is based on the silicon integrated circuit. Gold contacts play a key role in the fabrication of integrated circuits. For microwave devices and integrated circuits made from compound semiconductors such as gallium arsenide, gold metallization is used for both ohmic and rectifying contacts.
The dominant spin relaxation mechanism in compound organic semiconductors  [PDF]
Supriyo Bandyopadhyay
Physics , 2010, DOI: 10.1103/PhysRevB.81.153202
Abstract: Despite the recent interest in "organic spintronics", the dominant spin relaxation mechanism of electrons or holes in an organic compound semiconductor has not been conclusively identified. There have been sporadic suggestions that it might be hyperfine interaction caused by background nuclear spins, but no confirmatory evidence to support this has ever been presented. Here, we report the electric-field dependence of the spin diffusion length in an organic spin-valve structure consisting of an Alq3 spacer layer, and argue that this data, as well as available data on the temperature dependence of this length, contradict the notion that hyperfine interactions relax spin. Instead, they suggest that the Elliott-Yafet mechanism, arising from spin-orbit interaction, is more likely the dominant spin relaxing mechanism.
Realization of spin gapless semiconductors: the Heusler compound Mn2CoAl  [PDF]
Siham Ouardi,Gerhard H. Fecher,Jürgen Kübler,Claudia Felser
Physics , 2012, DOI: 10.1103/PhysRevLett.110.100401
Abstract: Recent studies have reported an interesting class of semiconductor materials that bridge the gap between semiconductors and halfmetallic ferromagnets. These materials, called spin gapless semiconductors, exhibit a bandgap in one of the spin channels and a zero bandgap in the other and thus allow for tunable spin transport. Here, a theoretical and experimental study of the spin gapless Heusler compound Mn2CoAl is presented. It turns out that Mn2CoAl is a very peculiar ferrimagnetic semiconductor with a magnetic moment of 2 {\mu}B and a high Curie temperature of 720 K. Below 300 K, the compound exhibits nearly temperature-independent conductivity, very low, temperature-independent carrier concentration, and a vanishing Seebeck coefficient. The magnetoresistance changes sign with temperature. In high fields, it is positive and non-saturating at low temperatures, but negative and saturating at high temperatures. The anomalous Hall effect is comparatively low, which is explained by the close antisymmetry of the Berry curvature for kz of opposite sign.
One-Dimensional Nanostructures and Devices of II–V Group Semiconductors  [cached]
Shen Guozhen,Chen Di
Nanoscale Research Letters , 2009,
Abstract: The II–V group semiconductors, with narrow band gaps, are important materials with many applications in infrared detectors, lasers, solar cells, ultrasonic multipliers, and Hall generators. Since the first report on trumpet-like Zn3P2nanowires, one-dimensional (1-D) nanostructures of II–V group semiconductors have attracted great research attention recently because these special 1-D nanostructures may find applications in fabricating new electronic and optoelectronic nanoscale devices. This article covers the 1-D II–V semiconducting nanostructures that have been synthesized till now, focusing on nanotubes, nanowires, nanobelts, and special nanostructures like heterostructured nanowires. Novel electronic and optoelectronic devices built on 1-D II–V semiconducting nanostructures will also be discussed, which include metal–insulator-semiconductor field-effect transistors, metal-semiconductor field-effect transistors, andp–nheterojunction photodiode. We intent to provide the readers a brief account of these exciting research activities.

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