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21 Jan 2002

Volume 80, Issue 3, pp. 341-531

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Large size dependence of exciton-longitudinal-optical-phonon coupling in nitride-based quantum wells and quantum boxes

S. Kalliakos, X. B. Zhang, T. Taliercio, P. Lefebvre, B. Gil, N. Grandjean, B. Damilano, and J. Massies

Appl. Phys. Lett. 80, 428 (2002); http://dx.doi.org/10.1063/1.1433165 (3 pages) | Cited 34 times

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We present an experimental and theoretical study of the size dependence of the coupling between electron–hole pairs and longitudinal-optical phonons in Ga1−xInxN/GaN-based quantum wells and quantum boxes. We found that the Huang–Rhys factor S, which determines the distribution of luminescence intensities between the phonon replicas and the zero-phonon peak, increases significantly when the vertical size of the boxes or the thickness of quantum well increases. We assign this variation to (1) the strong electric field present along the growth axis of the system, due to spontaneous and piezoelectric polarizations in these wurtzite materials, and (2) the localization on separate sites of electrons and holes in the plane of the wells or boxes, due to potential fluctuations in the ternary alloy. Indeed, envelope-function calculations for free or localized excitons, with electron–hole distance only controlled by Coulomb interaction, do not account quantitatively for the measured behavior of the S factor. In fact, the latter is rather similar to what is obtained for donor–acceptor pairs, with a statistical distribution of distances between localization centers for electrons and holes. © 2002 American Institute of Physics.
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63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
63.20.kk Phonon interactions with other quasiparticles
78.67.De Quantum wells
78.55.Cr III-V semiconductors

Cyclotron resonance and magnetotransport measurements in AlxGa1−xN/GaN heterostructures for x = 0.15–0.30

Z.-F. Li, W. Lu, S. C. Shen, S. Holland, C. M. Hu, D. Heitmann, B. Shen, Y. D. Zheng, T. Someya, and Y. Arakawa

Appl. Phys. Lett. 80, 431 (2002); http://dx.doi.org/10.1063/1.1435074 (3 pages) | Cited 6 times

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Cyclotron resonance (CR) and magnetotransport experiments have been performed on modulation Si-doped AlxGa1−xN/GaN heterostructures with aluminum fraction x varying from 0.15 to 0.30. A clear CR absorption and Shubnikov–de Haas oscillations have been observed. The CR line shapes are analyzed by calculating the high frequency conductivity of a two-dimensional electron gas. The obtained electron effective mass m∗ and scattering time τ are found to depend on the aluminum fraction x. For x = 0.30 the measured CR frequency shifts significantly upward, which demonstrates the formation of potential fluctuations in AlxGa1−xN/GaN heterostructures with large aluminum fraction x. © 2002 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.My Galvanomagnetic and other magnetotransport effects
76.40.+b Diamagnetic and cyclotron resonances
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
73.20.At Surface states, band structure, electron density of states

Quantum-interference characteristics of a 25 nm trench-type InGaAs/InAlAs quantum-wire field-effect transistor

T. Sugaya, J. P. Bird, M. Ogura, Y. Sugiyama, D. K. Ferry, and K.-Y. Jang

Appl. Phys. Lett. 80, 434 (2002); http://dx.doi.org/10.1063/1.1434304 (3 pages) | Cited 14 times

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We study the quantum-interference characteristics of a 25 nm, trench-type, InGaAs quantum-wire field-effect transistor realized by selective epitaxy, and find very different behavior from that typically exhibited by disordered wires. The amplitude of the magnetoresistance fluctuations is exponentially suppressed at high fields, where evidence of an Aharonov–Bohm effect is observed. The exponential suppression appears to be consistent with theoretical predictions for the influence of magnetic field on the scattering rate in clean wires, while the Aharonov–Bohm effect points to an interference process in which the one-dimensional subbands of the wire themselves constitute well-resolved paths for electron interference. © 2002 American Institute of Physics.
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85.35.Ds Quantum interference devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.63.Nm Quantum wires
85.30.Tv Field effect devices
72.20.My Galvanomagnetic and other magnetotransport effects
85.30.De Semiconductor-device characterization, design, and modeling

Analysis of photoexcited charge carrier density profiles in Si wafers by using an infrared camera

Rolf Brendel, Michael Bail, Benno Bodmann, Jörg Kentsch, and Max Schulz

Appl. Phys. Lett. 80, 437 (2002); http://dx.doi.org/10.1063/1.1434308 (3 pages) | Cited 2 times

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We demonstrate the mapping of lateral photoexcited charge carrier density profiles in a Si wafer that is illuminated in a spot by strongly absorbed light, using an infrared camera. The radial decay measured for the charge carrier density yields information on the effective carrier lifetime. The lifetime is extracted from the infrared camera image by modeling the transport. The carrier lifetime determined with the infrared camera technique is in accord with results obtained by conventional transient microwave reflectance measurements. © 2002 American Institute of Physics.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Cw Elemental semiconductors
72.40.+w Photoconduction and photovoltaic effects
81.05.Cy Elemental semiconductors
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)

Hole and electron field-effect mobilities in nanocrystalline silicon deposited at 150 °C

I-Chun Cheng and Sigurd Wagner

Appl. Phys. Lett. 80, 440 (2002); http://dx.doi.org/10.1063/1.1435798 (3 pages) | Cited 51 times

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Field-effect structures were made from nanocrystalline silicon (nc-Si:H) deposited at a substrate temperature of 150 °C by plasma-enhanced chemical vapor deposition excited at 80 MHz. The nc-Si:H channel layer was grown on top of a separate nc-Si:H buffer and seed layer that serves to develop the crystalline structure. Staggering the contacts and the gate ensures that mobilities are measured precisely in the last-to-grow nc-Si:H layer. The hole mobility in saturation reaches 0.06–0.2 cm2 V−1 s−1 and the electron mobility ∼12 cm2 V−1 s−1. These results suggest that large-area circuits of complementary p- and n-channel devices can be made from nc-Si:H deposited on low-temperature substrates. © 2002 American Institute of Physics.
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73.61.Cw Elemental semiconductors
72.80.Cw Elemental semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
72.20.Fr Low-field transport and mobility; piezoresistance
73.63.Bd Nanocrystalline materials

Photoluminescence properties of MgS/CdSe quantum wells and quantum dots

M. Funato, A. Balocchi, C. Bradford, K. A. Prior, and B. C. Cavenett

Appl. Phys. Lett. 80, 443 (2002); http://dx.doi.org/10.1063/1.1435407 (3 pages) | Cited 11 times

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The optical properties of MgS/CdSe quantum structures grown by molecular beam epitaxy are characterized by photoluminescence (PL) spectroscopy. The increase in the CdSe thickness from 1 to beyond 3 ML results in the formation of, at first, quantum wells (QWs) and then quantum dots (QDs) by Stranski–Krastanov growth. The PL temperature dependence measurements reveal that, in the QWs, excitons localized by potential fluctuations principally govern the PL properties, which is in strong contrast to the QD PL properties. © 2002 American Institute of Physics.
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78.55.Et II-VI semiconductors
78.67.De Quantum wells
78.67.Hc Quantum dots
73.21.Fg Quantum wells
71.35.-y Excitons and related phenomena
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.21.La Quantum dots

GaN metal–oxide–semiconductor structures using Ga-oxide dielectrics formed by photoelectrochemical oxidation

D. J. Fu, Y. H. Kwon, T. W. Kang, C. J. Park, K. H. Baek, H. Y. Cho, D. H. Shin, C. H. Lee, and K. S. Chung

Appl. Phys. Lett. 80, 446 (2002); http://dx.doi.org/10.1063/1.1436279 (3 pages) | Cited 30 times

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GaN metal–oxide–semiconductor (MOS) capacitors were fabricated by using Ga oxide formed by photoelectrochemical oxidation of GaN. The electrical properties of the MOS structures as characterized by capacitance–voltage measurement were found to be dependent on the oxidation time and posttreatment. Positive flatband voltage was observed in devices with thin oxide layers indicating the existence of negative oxide charge. Very thin oxide exhibits high capacitance and reverse leakage, which can be reduced by rapid thermal annealing (RTA). Passivation of the interface by RTA is partially responsible for the improvement. Thicker oxide layers exhibit improved electrical properties. Low density of interface states ( ∼ 1011 eV−1 cm−2) was obtained in the Ga-oxide/GaN structure grown under optimized conditions. © 2002 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.65.Mq Oxidation
82.45.-h Electrochemistry and electrophoresis
82.50.-m Photochemistry
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
73.20.At Surface states, band structure, electron density of states
81.05.Ea III-V semiconductors
81.65.Rv Passivation
82.45.Jn Surface structure, reactivity and catalysis
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
84.32.Tt Capacitors
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