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1 May 2003

Volume 93, Issue 9, pp. 4955-5841

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Phonon modes of GaN/AlN heterojunction field-effect transistor structures grown on Si(111) substrates

B. Pattada, Jiayu Chen, M. O. Manasreh, S. Guo, D. Gotthold, M. Pophristic, and B. Peres

J. Appl. Phys. 93, 5824 (2003); http://dx.doi.org/10.1063/1.1561583 (3 pages)

Online Publication Date: 16 April 2003

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Phonon modes of GaN/AlN heterojunction field-effect transistor (HFET) structures were investigated using Fourier-transform infrared spectroscopy. The HFET structure was grown on Si(111) substrate with AlN-based buffer layers. The phonon modes were also investigated in structure without AlGaN cap layer. The phonon mode spectra were obtained at the normal incident, waveguide, and Brewster’s angle configurations. Several vibrational frequencies were observed and found to be strongly dependent on the angle of the incident light. In particular, a phonon frequency of ∼734 cm−1 was observed only in the spectra when the samples are in the Brewster’s angle configuration. Moreover, a phonon mode was observed at 880 cm−1 in both waveguide and Brewster’s angle configurations. Additionally, a phonon absorption band is observed around 576 cm−1 , which appears to be composed of two modes, was redshifted to ∼550 cm−1 when the spectra were recorded in the waveguide configuration. © 2003 American Institute of Physics.
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63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.67.De Quantum wells
85.30.Tv Field effect devices
78.30.Fs III-V and II-VI semiconductors
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Focused ion beam prepared contacts of tungsten to silicon characterized by a cross-bridge Kelvin resistor approach

H. Langfischer and E. Bertagnolli

J. Appl. Phys. 93, 5827 (2003); http://dx.doi.org/10.1063/1.1562738 (3 pages) | Cited 3 times

Online Publication Date: 16 April 2003

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Focused ion beam (FIB) chemical vapor deposition of tungsten is widely used for circuit repair and prototyping. An extension of this direct write approach from the interconnect metalization level to the device level in complementary metal-oxide-semiconductor technology requires the demonstration of ohmic low resistance contacts to both types of highly doped source and drain regions. We investigated the metal-silicon contacts of 50 keV Ga+ FIB deposited tungsten by a cross-bridge Kelvin resistor approach to extract the contact resistances and we found nonrectifying contacts to both p+- and n+-silicon. For p+-silicon a resistivity of 5.33×10−6 Ω cm2, whereas for n+-silicon a higher value of 9.96×10−3 Ω cm2 is found. Thermal treatment at 450 °C for 15 min deteriorates the contact properties of p+-silicon. In contrast, the annealing process reduced the resistivity of the tungsten to n+-silicon contacts by factor of 100 to a value of 1.07×10−4 Ω cm2. © 2003 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
85.40.Ls Metallization, contacts, interconnects; device isolation
73.61.Cw Elemental semiconductors
61.72.Cc Kinetics of defect formation and annealing

Resonant magnetotunneling of photogenerated holes in double barrier structures

A. Vercik, Y. Galvão Gobato, A. C. Rodrigues Bittencourt, G. E. Marques, M. J. S. P. Brasil, and C. Trallero-Giner

J. Appl. Phys. 93, 5830 (2003); http://dx.doi.org/10.1063/1.1563057 (3 pages) | Cited 2 times

Online Publication Date: 16 April 2003

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In this work, we report on a technique—namely, the photoinduced magnetotunneling technique—which allows the direct experimental observation of tunneling of holes through valence-band Landau levels in n-i-n double-barrier resonant tunneling structures. Photocurrent–voltage curves exhibit several peaks associated with the complex nature of the dispersion of holes under parallel electric and magnetic fields applied to the sample. © 2003 American Institute of Physics.
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72.25.Mk Spin transport through interfaces
73.20.At Surface states, band structure, electron density of states
75.45.+j Macroscopic quantum phenomena in magnetic systems
73.40.Gk Tunneling
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Characterization of traps related to InAs quantum-dot growth-induced defects in GaAs by low-frequency noise measurements in reverse-biased Schottky diodes

N. A. Hastas, C. A. Dimitriadis, L. Dozsa, E. Gombia, and R. Mosca

J. Appl. Phys. 93, 5833 (2003); http://dx.doi.org/10.1063/1.1564879 (3 pages) | Cited 1 time

Online Publication Date: 16 April 2003

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The trap properties of Au/n-GaAs Schottky diodes, with self-organized InAs quantum dots (QDs) confined between buffer and capping GaAs layers on n+-GaAs substrates, are investigated by low-frequency noise measurements. The noise data indicate that the trap density at the interface of the buffer/capping GaAs layers is higher by about one order of magnitude than the trap density at the Au/GaAs interface. In samples with the QD-structure, deep traps are created within the buffer GaAs layer due to QD formation, with a trap density higher by about three orders of magnitude than the trap density at the Au/GaAs interface. Conduction measurements show that in Schottky diodes without QDs, the increase in the leakage current is due to an interfacial layer contributing to the barrier height lowering. In Schottky diodes comprising QDs, an anomalous leakage current is observed, attributed to local generation of deep traps due to QD formation. © 2003 American Institute of Physics.
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85.30.Kk Junction diodes
85.30.Hi Surface barrier, boundary, and point contact devices
85.30.De Semiconductor-device characterization, design, and modeling
73.21.La Quantum dots
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.20.-r Electron states at surfaces and interfaces
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.07.Ta Quantum dots

Effects of tensile strain in barrier on optical gain spectra of GaInNAs/GaAsN quantum wells

W. J. Fan, S. T. Ng, S. F. Yoon, M. F. Li, and T. C. Chong

J. Appl. Phys. 93, 5836 (2003); http://dx.doi.org/10.1063/1.1566469 (3 pages) | Cited 11 times

Online Publication Date: 16 April 2003

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The band structures, optical gain spectra, and transparency radiative current densities of compressive-strained GaInNAs quantum wells (QWs) with different tensile-strained GaAsN (N composition from 0 to 3%) barriers are systematically investigated using a modified 6×6 k⋅p Hamiltonian including the heavy hole, light hole, and spin-orbit splitting bands. We found that the transition energy decreases when increasing the N composition in the barrier. The optical gain spectra and maximum optical gain as a function of carrier density and radiative current density are obtained for the GaInNAs/GaAsN QWs with well width of 5 nm, InW=28%, and NW=2.66% emitting around 1.55 μm. The transparency carrier density increases with the nitrogen composition in the GaAsN barrier. The transparency radiative current density decreases with more nitrogen being added into the barrier, which is in agreement with the recent experimental observation. © 2003 American Institute of Physics.
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78.67.De Quantum wells
68.65.Fg Quantum wells
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
73.21.Fg Quantum wells
81.07.St Quantum wells
81.05.Ea III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.20.Nr Semiconductor compounds
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
71.15.-m Methods of electronic structure calculations
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Effect of a nucleating agent on lamellar growth in melt-crystallizing polyethylene oxide

F. Aliotta, G. Di Marco, R. Ober, and M. Pieruccini

J. Appl. Phys. 93, 5839 (2003); http://dx.doi.org/10.1063/1.1564877 (3 pages) | Cited 2 times

Online Publication Date: 16 April 2003

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The effects of a (non co-crystallizing) nucleating agent on secondary nucleation rate and final lamellar thickness in isothermally melt-crystallizing polyethylene oxide are considered. Small angle x-ray scattering reveals that lamellae formed in nucleated samples are thinner than in the pure samples crystallized at the same undercoolings. These results are in quantitative agreement with growth rate data obtained by calorimetry, and are interpreted as the effect of a local decrease of the basal surface tension, determined mainly by the nucleant molecules diffused out of the regions being about to crystallize. Quantitative agreement with a simple lattice model allows for some interpretation of the mechanism. © 2003 American Institute of Physics.
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61.41.+e Polymers, elastomers, and plastics
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
64.70.K- Solid-solid transitions
78.70.Ck X-ray scattering
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