jap banner
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

1 Oct 2005

Volume 98, Issue 7, Articles (07xxxx)

Return to All Sections
back to top
RSS Feeds

An impedance spectroscopic study of n-type phosphorus-doped diamond

Stephane Curat, Haitao Ye, Olivier Gaudin, Richard B. Jackman, and Satoshi Koizumi

J. Appl. Phys. 98, 073701 (2005); http://dx.doi.org/10.1063/1.2058183 (6 pages) | Cited 8 times

Online Publication Date: 4 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
An important development in the field of diamond electronics has been the production of n-type electrical characteristics following homoepitaxial diamond growth on (111) diamond in the presence of phosphorus-containing gases. Several studies have reported that a phosphorus donor level forms with an activation energy in the range of 0.43–0.6 eV; the ground state for the donor level is considered to be at 0.6 eV. Little is currently known about other electrically active defects that may be produced alongside the donor state when phosphorus is introduced. In this paper we report upon the use of impedance spectroscopy, which can isolate the differing components that contribute to the overall conductivity of the film. In Cole-Cole plots, two semicircular responses are observed for all temperatures above 75 °C; a single semicircle being seen at temperatures below this. The results suggest the presence of two conduction paths with activation energies of 0.53 and 0.197 eV. The former can be attributed to the phosphorus donor level, being lower than 0.6 eV due to reduced mobility within the film at elevated temperatures. The latter is discussed in terms of defects in the P+-doped region under the Ohmic contacts being used.
Show PACS
73.61.Cw Elemental semiconductors
71.55.Cn Elemental semiconductors
61.72.up Other materials

Magnesium/nitrogen and beryllium/nitrogen coimplantation into GaN

K. T. Liu, Y. K. Su, S. J. Chang, and Y. Horikoshi

J. Appl. Phys. 98, 073702 (2005); http://dx.doi.org/10.1063/1.2073969 (5 pages) | Cited 3 times

Online Publication Date: 4 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The nitrogen coimplantation characteristics in the Mg- and Be-implanted GaN with different dopant concentration ratios have been systematically investigated. The Hall-effect measurements show that the p-type characteristics are produced in the Mg- and Be-implanted GaN by the coimplantation of N atoms and subsequent annealing, which is essentially related to the column II/V dopant concentration ratio and annealing condition. This behavior may be attributed to the reduction of self-compensation induced by N vacancies and the enhanced acceptor substitution, which is in reasonable agreement with the surface stoichiometric switching determined by x-ray photoelectron spectroscopy measurements. From photoluminescence data, the activation energy of the Be acceptor level is evaluated to be about 145 meV, which is shallower than that of the Mg acceptor. These experimental results indicate that the selective-area N coimplantation with Mg and Be atoms into GaN is an effective method to enhance the p-type conductivity and to improve the p-type Ohmic contact resistance.
Show PACS
61.72.uj III-V and II-VI semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
61.72.S- Impurities in crystals
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
72.20.My Galvanomagnetic and other magnetotransport effects
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters
79.60.Bm Clean metal, semiconductor, and insulator surfaces

High mobility undoped amorphous indium zinc oxide transparent thin films

Bhupendra Kumar, Hao Gong, and Ramam Akkipeddi

J. Appl. Phys. 98, 073703 (2005); http://dx.doi.org/10.1063/1.2060957 (5 pages) | Cited 17 times

Online Publication Date: 4 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We investigated the amorphous region of the In2O3‐ZnO material system. The composition dependence of the amorphous region was explored and the films exhibited an n-type semiconductor behavior with low resistivities in the range of 4×10−4–6.33×10−4 Ωcm. These amorphous films have a very wide transmittance window range of 300–2500 nm, and the transmittance is higher than 85% in the fiber-optics telecommunication window of 1.30–1.55 μm. The band gap of amorphous films can be engineered from 2.66 to 3.05 eV, by varying the zinc/(zinc+indium) atomic ratio. A monotonous decrease in mobility from 71.6 to 59.4 cm2/V s was observed with an increase in zinc/(zinc+indium) atomic ratio from 0.19 to 0.43 in the amorphous region. This trend was explained on the basis of percolation theory and overlap integral calculations. The effective mass of these amorphous films was calculated using the Drude model in the free-carrier absorption region and correlated with composition as well as the carrier concentration of the films.
Show PACS
72.20.Fr Low-field transport and mobility; piezoresistance
73.61.Jc Amorphous semiconductors; glasses
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
73.50.Dn Low-field transport and mobility; piezoresistance
73.61.Ga II-VI semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Large magnetoresistance in rapidly solidified bismuth

Kyongha Kang, Y. F. Hu, L. H. Lewis, Qiang Li, A. R. Moodenbaugh, and Young-Suk Choi

J. Appl. Phys. 98, 073704 (2005); http://dx.doi.org/10.1063/1.2067706 (4 pages) | Cited 2 times

Online Publication Date: 6 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Rapidly solidified, annealed ribbons (20 μm thick) of elemental Bi show a room-temperature ordinary magnetoresistive effect of 250% at 5 T with the field applied perpendicular to the ribbon surface. The effect increases to 10000% at 5 K and 5 T. These values are intermediate to those obtained for single-crystal Bi films and sputtered or evaporated polycrystalline Bi films of comparable thicknesses. The large magnetoresistance of the ribbons is attributed to a very good crystallinity and partial c-axis texture of the ribbon achieved during solidification. Rapid solidification by melt spinning is a promising technique for synthesis of Bi with potential application in magnetoelectric devices.
Show PACS
75.47.Gk Colossal magnetoresistance
75.70.Ak Magnetic properties of monolayers and thin films
64.70.D- Solid-liquid transitions
81.40.Gh Other heat and thermomechanical treatments
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Large tunnel magnetoresistance with plasma oxidized MgO barrier

T. Dimopoulos, G. Gieres, J. Wecker, N. Wiese, Y. Luo, and K. Samwer

J. Appl. Phys. 98, 073705 (2005); http://dx.doi.org/10.1063/1.2077847 (5 pages) | Cited 9 times

Online Publication Date: 6 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This work focuses on magnetic tunnel junctions with a polycrystalline MgO barrier, prepared by plasma oxidation. Combined with Co50Fe50 ferromagnetic electrodes, a large tunnel magnetoresistance (TMR) of 60% is obtained at room temperature. The TMR effect is comparable to state-of-the-art Al oxide barriers with amorphous CoFeB electrodes. It is also found to decrease with the MgO thickness. Two most significant advantages of the MgO junctions are pointed out: (a) The resistance-area product is approximately two orders of magnitude lower than for AlOX− based junctions of the same thickness. (b) MgO presents unsurpassed thermal stability for high annealing temperatures (up to 370 °C) and long annealing periods. In addition, for small, patterned elements, we have tested the switching behavior of the soft electrode grown on the polycrystalline MgO barrier.
Show PACS
73.40.Gk Tunneling
73.40.Rw Metal-insulator-metal structures

Magnetoresistance flipping of Fe/Ru multilayers prepared by electron-beam evaporation

K. W. Geng, Y. Gu, D. Xu, C. Song, and F. Pan

J. Appl. Phys. 98, 073706 (2005); http://dx.doi.org/10.1063/1.2081110 (5 pages)

Online Publication Date: 7 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Fe/Ru multilayers were prepared by electron-beam evaporation. The magnetoresistance (MR) properties of the multilayer switched the MR sign with the Fe and Ru layer thickness. When the thickness of magnetic Fe layers was fixed at 1.2 nm, the MR effects of the multilayer transformed from a negative to a positive one, with the thickness of nonmagnetic Ru layer changed from 1.2 to 5.0 nm. While when the thickness of nonmagnetic Ru layers was fixed, the transformation of the MR effect is inversed, i.e., transformed from a positive to a negative one with the thickness of the magnetic Fe layer increased. The origin of the MR variation is analyzed. The inverse giant magnetoresistance is related to the Fe/Ru interface layer, in which the scattering spin asymmetry is less than 1. The MR dependence on the Fe and Ru layer thickness reveals the competition between two mechanisms of normal MR and inverse MR
Show PACS
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Bb Fe and its alloys
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.47.De Giant magnetoresistance
75.60.-d Domain effects, magnetization curves, and hysteresis
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)

Enhancement of the thermoelectric figure of merit in M/T/M (M = Cu or Ni and T = Bi0.88Sb0.12) composite materials

Osamu Yamashita, Kouji Satou, Hirotaka Odahara, and Shoichi Tomiyoshi

J. Appl. Phys. 98, 073707 (2005); http://dx.doi.org/10.1063/1.2081113 (8 pages) | Cited 10 times

Online Publication Date: 10 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The resultant thermoelectric figure of merit ZT of M/T/M (M = Cu or Ni and T = Bi0.88Sb0.12) composite materials welded with Bi–Sb alloy was measured at 298 K as a function of relative thickness of Bi–Sb alloy and compared with ZT values calculated by treating it as an electrical and thermal circuit. It was first clarified experimentally that the observed ZT values of composite materials have a local maximum at an optimum volume fraction (corresponding to the thickness) of Bi–Sb alloy in spite of macroscopic composite materials, owing to a significant enhancement in the Seebeck coefficient. It is sure that the enhancement in α is caused by the boundary Seebeck coefficient generated at the interface between Bi–Sb alloy and a metal. It was thus clarified that the interface effect appears clearly in macroscopic systems. The observed maximum ZT values at 298 K reached a surprisingly great value of 0.44 at a relative thickness of approximately 0.7, which corresponds to approximately 1.7 times as large as 0.26 of Bi0.88Sb0.12 alloy and to about half of 0.8–0.9 of commercially utilized bismuth telluride compounds. So enhanced ZT may not be utilizable for a Peltier module, but is available for generators.
Show PACS
72.15.Jf Thermoelectric and thermomagnetic effects
72.20.Pa Thermoelectric and thermomagnetic effects
72.80.Tm Composite materials

Influence of growth temperature on minority-carrier lifetime of Si layer grown by liquid phase epitaxy using Ga solvent

Yusuke Satoh, Noritaka Usami, Wugen Pan, Kozo Fujiwara, Kazuo Nakajima, and Toru Ujihara

J. Appl. Phys. 98, 073708 (2005); http://dx.doi.org/10.1063/1.2061891 (4 pages) | Cited 1 time

Online Publication Date: 11 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The influence of growth temperature on the minority-carrier lifetime of epitaxial Si layers was systematically investigated. Epitaxial Si layers were grown on (111) Si substrates in the temperature range of 500–900 °C by liquid phase epitaxy using Ga solvent. To ensure that the contribution of the annealed Si substrate during growth will be excluded, the overall lifetime of the epitaxial layer and the Si substrate was measured as a function of the thickness of the substrate. This procedure revealed that the minority-carrier lifetime of the epitaxial Si layers increases upon lowering the growth temperature. This can be explained by the lower impurity concentration as measured by secondary-ion mass spectroscopy. Moreover, the existence of a slightly misoriented crystal domain was found in the Si layer grown at a high temperature. These results suggest that low growth temperature should be employed in growing a Si film with high minority-carrier lifetime.
Show PACS
81.05.Cy Elemental semiconductors
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
73.61.Cw Elemental semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Carrier capture before entering into a semiconductor quantum dot as a dominant pathway for the reduction of emission efficiency

E. G. Lee, M. D. Kim, D. Lee, and S. G. Kim

J. Appl. Phys. 98, 073709 (2005); http://dx.doi.org/10.1063/1.2081108 (3 pages) | Cited 2 times

Online Publication Date: 11 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
To study the carrier reduction pathway for quantum dots (QDs), we have measured carrier lifetimes and photoluminescence spectra both at 10 K and at higher temperatures. We found that the carriers captured in QDs are robust and are not lost to nearby defects, even at elevated temperature, and that the lower emission efficiency of QDs with defects compared to the corresponding defect-free QDs is due to the capture of carriers to defects before entering into the QDs.
Show PACS
81.07.Ta Quantum dots
81.05.Ea III-V semiconductors
73.21.La Quantum dots
73.63.Kv Quantum dots
78.67.Hc Quantum dots
78.55.Cr III-V semiconductors

Interface states in polymer metal-insulator-semiconductor devices

I. Torres and D. M. Taylor

J. Appl. Phys. 98, 073710 (2005); http://dx.doi.org/10.1063/1.2081109 (9 pages) | Cited 35 times

Online Publication Date: 12 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The admittance of polymer metal-insulator-semiconductor (MIS) capacitors has been measured as a function of frequency and applied voltage. The results reveal the presence of hole trapping states at the interface of the polysilsesquioxane insulator and the poly(3-hexylthiophene) semiconductor. The states appear to be distributed in two bands: one close to the equilibrium Fermi level at the semiconductor surface, the other ∼ 0.5 eV above. Annealing the devices under vacuum for several hours at 90 °C increases the concentration of the shallower traps to ∼ 3×1012 cm−2 eV−1, while decreasing the concentration of deep traps to ∼ 1×1010 cm−2 eV−1. Annealing improves the bulk hole mobility to ∼ 1×10−4 cm2 V−1 s−1 while reducing the field-effect mobility in MIS field-effect transistors (FETs) slightly to ∼ 7×10−3 cm2 V−1 s−1. Although the concentration of interface states is sufficiently great to account for gate-bias-induced threshold voltage instability in MISFETs, their associated time constants are much too short to explain the long term nature of the instability.
Show PACS
85.30.Tv Field effect devices
84.32.Tt Capacitors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.20.At Surface states, band structure, electron density of states
71.55.Ht Other nonmetals
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.20.Fr Low-field transport and mobility; piezoresistance
61.72.Cc Kinetics of defect formation and annealing
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)

Split donor centers and split excitons in a semiconductor heterostructure

Z. S. Gribnikov and G. I. Haddad

J. Appl. Phys. 98, 073711 (2005); http://dx.doi.org/10.1063/1.2084317 (7 pages)

Online Publication Date: 14 October 2005

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The first subject considered in the article is a donor center embedded in a thin heterostructural barrier separating a semiconductor medium into two halves. As a result of the small thickness of this barrier, the wave function of an electron bound by the donor center shifts almost completely into both halves of the surrounding semiconductor medium. The ground and first excited electron states of such a donor center are separated from each other by a narrow energy gap determined by the symmetric-antisymmetric tunnel splitting. Such structures can be implemented in both GaAs/AlXGa1−XAs and Si/GeXSi1−X material systems. The second considered subject is an exciton formed in analogous heterostructures when the staggered band alignment takes place between the heterobarrier and semiconductor medium. As a result of such band alignment, the hole participating in the exciton creation is located in the formed quantum well and the electron, which is the hole’s opponent, is separated into halves (on different sides of the quantum well) as before. Unlike the donor center, the exciton can be shifted and localized in arbitrary positions along the staggered “barrier-well” boundary by inhomogeneous electric fields of external controlling gates.
Show PACS
73.21.Fg Quantum wells
71.55.Eq III-V semiconductors
71.55.Cn Elemental semiconductors
71.35.-y Excitons and related phenomena
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close