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3 Nov 2003

Volume 83, Issue 18, pp. 3647-3835

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Appl. Phys. Lett. 83, 3737 (2003); http://dx.doi.org/10.1063/1.1623315 (3 pages)

Ian Appelbaum, D. J. Monsma, K. J. Russell, V. Narayanamurti, and C. M. Marcus
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Thermal detrapping analysis of pumping-related defects in diamond

Marco Marinelli, E. Milani, M. E. Morgada, G. Pucella, G. Rodriguez, A. Tucciarone, G. Verona-Rinati, M. Angelone, and M. Pillon

Appl. Phys. Lett. 83, 3707 (2003); http://dx.doi.org/10.1063/1.1623318 (3 pages) | Cited 3 times

Online Publication Date: 28 October 2003

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A method is presented to selectively characterize the traps involved in the pumping procedure of diamond films. The pumping process strongly reduces the concentration of active carrier trapping centers, leading to an enhancement of electronic properties of such material, and is obtained by irradiating the diamond films with ionizing radiation. Since the improved transport properties lead to an increased efficiency when diamond films are used as radiation detectors, valuable information on this process can be obtained by analyzing the response of diamond based particle detectors. For this purpose a high-quality diamond film was grown by microwave chemical vapor deposition and a particle detector was realized. Its response to a 5.5-MeV 241Am α-particles was measured after successive annealing steps performed at different temperatures in the 180–228 °C range. Before each annealing curve at a given temperature, the detector was driven to the pumped state through β-particle irradiation. The efficiency versus annealing time curves evidence a thermally induced detrapping, confirming the pumping mechanism as a filling and consequent passivation of defects. The analysis of the decay time of the detector efficiency as a function of temperature allows the determination of the activation energy of these defects, which is Ea = 1.62±0.15 eV. © 2003 American Institute of Physics.
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29.40.Wk Solid-state detectors
81.05.U- Carbon/carbon-based materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.55.Cn Elemental semiconductors

Metastability of two-hydrogen complexes in silicon

D. J. Chadi

Appl. Phys. Lett. 83, 3710 (2003); http://dx.doi.org/10.1063/1.1624476 (3 pages) | Cited 7 times

Online Publication Date: 28 October 2003

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A two-hydrogen interstitial complex (H2∗∗) in crystalline Si that exhibits metastability is proposed via first-principles total energy calculations. In its most stable state, H2∗∗ is 0.28 eV/H higher in energy than H2∗ and is electron-spin-resonance inactive. The complex has a metastable spin active state arising from a Si dangling-bond in which the H–H separation is 2.39 Å. The properties of H2∗∗ make it a promising candidate for the defect responsible for the Staebler–Wronski effect in amorphous Si. © 2003 American Institute of Physics.
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71.55.Cn Elemental semiconductors
61.72.J- Point defects and defect clusters
76.30.Mi Color centers and other defects

Oxidation rate enhancement of SiGe epitaxial films oxidized in dry ambient

M. Spadafora, G. Privitera, A. Terrasi, S. Scalese, C. Bongiorno, A. Carnera, M. Di Marino, and E. Napolitani

Appl. Phys. Lett. 83, 3713 (2003); http://dx.doi.org/10.1063/1.1622439 (3 pages) | Cited 17 times

Online Publication Date: 28 October 2003

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We present a study on thin oxides obtained by rapid thermal oxidation of Si1−xGex epitaxial layers. The oxidation processes were performed in dry O2 at 1000 °C for times up to 600 s. Our data show an oxide growth rate enhancement with respect to pure Si. Except for a very small amount of GeO2 that is found at the surface, all the Ge is rejected towards the SiO2/SiGe interface, forming a Ge-enriched layer free of extended defects. The comparison of our results for dry processes with those reported in the literature for wet ambient supports the idea that the kinetics of SiGe oxidation is controlled by similar mechanisms in both cases, in contrast with models and interpretations so far proposed. © 2003 American Institute of Physics.
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81.65.Mq Oxidation
81.05.Hd Other semiconductors

Engineering carrier confinement potentials in 1.3-μm InAs/GaAs quantum dots with InAlAs layers: Enhancement of the high-temperature photoluminescence intensity

H. Y. Liu, I. R. Sellers, M. Hopkinson, C. N. Harrison, D. J. Mowbray, and M. S. Skolnick

Appl. Phys. Lett. 83, 3716 (2003); http://dx.doi.org/10.1063/1.1622443 (3 pages) | Cited 18 times

Online Publication Date: 28 October 2003

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We describe an optical study of structures consisting of an InAlAs-GaAs strained buffer layer and an InAlAs-InGaAs composite strain-reducing layer designed to modify the confining potential of 1.3-μm InAs/GaAs quantum dots (QDs). With increasing (decreasing) InAlAs (InGaAs) thickness in the strain-reducing layer grown above the QDs, the integrated photoluminescence (PL) intensity of the QD ground-state transition increases dramatically and the emission wavelength decreases slightly from 1.36 to 1.31 μm. The enhancement of PL efficiency is temperature dependent, being much greater above 200 K. A maximum enhancement of 450 is achieved at room temperature. This improvement of the high-temperature PL efficiency should lead to a significant improvement in the characteristics of 1.3-μm InAs/GaAs QD lasers. © 2003 American Institute of Physics.
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73.21.La Quantum dots
78.67.Hc Quantum dots
81.07.Ta Quantum dots
42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.05.Ea III-V semiconductors
78.55.Cr III-V semiconductors

Effect of quantum-well confinement on acceptor state lifetime in δ -doped GaAs/AlAs multiple quantum wells

W. M. Zheng, M. P. Halsall, P. Harrison, J.-P. R. Wells, I. V. Bradley, and M. J. Steer

Appl. Phys. Lett. 83, 3719 (2003); http://dx.doi.org/10.1063/1.1623950 (3 pages) | Cited 6 times

Online Publication Date: 28 October 2003

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Using far-infrared time-resolved spectroscopy, we have investigated the effect of quantum-well confinement on the lifetime of shallow acceptor states in GaAs/AlAs multiple quantum wells with Be δ-doping at the well center. Low-temperature far-infrared absorption measurements clearly show three principal absorption lines due to transitions of Be acceptor states from the ground state to the first three odd-parity excited states, respectively. It is found that the lifetime of excited states monotonically reduces with decreasing quantum-well width, from 350 ps in bulk to 55 ps in a 100 Å well. We suggest that the effect of quantum-well confinement on zone-fold acoustic-phonon modes increases the intra-acceptor scattering rate of acoustic-phonon-assisted relaxation. © 2003 American Institute of Physics.
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73.21.Fg Quantum wells
78.67.De Quantum wells
71.55.Eq III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
78.47.-p Spectroscopy of solid state dynamics
63.20.K- Phonon interactions
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Double-scaled potential profile in a group-III nitride alloy revealed by Monte Carlo simulation of exciton hopping

K. Kazlauskas, G. Tamulaitis, A. Žukauskas, M. A. Khan, J. W. Yang, J. Zhang, G. Simin, M. S. Shur, and R. Gaska

Appl. Phys. Lett. 83, 3722 (2003); http://dx.doi.org/10.1063/1.1625111 (3 pages) | Cited 29 times

Online Publication Date: 28 October 2003

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The temperature dependences of the peak position and width of the photoluminescence band in Al0.1In0.01Ga0.89N layers were explained by Monte Carlo simulation of exciton localization and hopping. The introduction of a doubled-scaled potential profile due to inhomogeneous distribution of indium allowed obtaining a good quantitative fit of the experimental data. Hopping of excitons was assumed to occur through localized states distributed on a 16 meV energy scale within the In-rich clusters with the average energy in these clusters dispersed on a larger (42 meV) scale. © 2003 American Institute of Physics.
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71.35.Cc Intrinsic properties of excitons; optical absorption spectra
78.55.Cr III-V semiconductors
02.70.Uu Applications of Monte Carlo methods

Light-induced defect states in hydrogenated amorphous silicon centered around 1.0 and 1.2 eV from the conduction band edge

J. M. Pearce, J. Deng, R. W. Collins, and C. R. Wronski

Appl. Phys. Lett. 83, 3725 (2003); http://dx.doi.org/10.1063/1.1624637 (3 pages) | Cited 8 times

Online Publication Date: 28 October 2003

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To take into account the presence of multiple light-induced defect states in hydrogenated amorphous silicon (a-Si:H) the evolution of the entire spectra of photoconductive subgap absorption, α(hν), has been analyzed. Using this approach two distinctly different light-induced defect states centered around 1.0 and 1.2 eV from the conduction band edge are clearly identified. Results are presented on their evolution and respective effects on carrier recombination that clearly point to the importance of these states in evaluating the stability of different a-Si:H solar cell materials, as well as elucidating the origin of the Staebler–Wronski effect. © 2003 American Institute of Physics.
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72.40.+w Photoconduction and photovoltaic effects
71.55.Cn Elemental semiconductors
71.55.Jv Disordered structures; amorphous and glassy solids
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Cw Elemental semiconductors
72.80.Ng Disordered solids

Inherent nature of localized states in highly planar monolayer InAs/GaAsN pseudo-alloys

I. L. Krestnikov, R. Heitz, N. N. Ledentsov, A. Hoffmann, A. M. Mintairov, T. H. Kosel, J. L. Merz, I. P. Soshnikov, and V. M. Ustinov

Appl. Phys. Lett. 83, 3728 (2003); http://dx.doi.org/10.1063/1.1623320 (3 pages) | Cited 3 times

Online Publication Date: 28 October 2003

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We have studied the optical properties of pseudo-alloy monolayer InAs/GaAsN superlattices with highly planar interfaces. In spite of the two-dimensional growth mode, we found that the photoluminescence (PL) reveals strong exciton localization through the whole PL band, dominating the spectrum up to high excitation densities and observation temperatures. Pump-and-probe PL experiments provide the following time constants: (a) the exciton relaxation time to the ground states of the localization regions is found to be ∼40–70 ps, depending on the photon energy, and (b) the time for depopulation of these localized states is between 2 and 4 ns. © 2003 American Institute of Physics.
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73.21.Cd Superlattices
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
68.35.Ct Interface structure and roughness
73.20.At Surface states, band structure, electron density of states
73.20.Fz Weak or Anderson localization
73.61.Ey III-V semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.22.Lp Collective excitations
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Intrinsic limits on electron mobility in dilute nitride semiconductors

S. Fahy and E. P. O’Reilly

Appl. Phys. Lett. 83, 3731 (2003); http://dx.doi.org/10.1063/1.1622444 (3 pages) | Cited 43 times

Online Publication Date: 28 October 2003

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A fundamental connection is established between the composition-dependence of the conduction band edge energy and the n-type carrier scattering cross section in the ultradilute limit for semiconductor alloys, imposing general limits on the carrier mobility in such alloys. From the measured nitrogen composition dependence of the bandgap in GaAs1−xNx, the carrier scattering cross section of substitutional nitrogen defects in GaAs is estimated to be 0.3 nm2. Within an independent scattering approximation, the carrier mobility is then estimated to be ∼ 1000 cm2/V s for a nitrogen atomic concentration of 1%, comparable to the highest measured mobility in high-quality GaInNAs samples at these N concentrations, but substantially higher than that found in many samples. This gives an intrinsic upper bound on the carrier mobility in these materials. © 2003 American Institute of Physics.
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72.20.Ee Mobility edges; hopping transport
72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Ey III-V and II-VI semiconductors
61.66.Bi Elemental solids
61.66.Dk Alloys
71.20.Nr Semiconductor compounds

Band offsets for the epitaxial TiO2/SrTiO3/Si(001) system

A. C. Tuan, T. C. Kaspar, T. Droubay, J. W. Rogers, and S. A. Chambers

Appl. Phys. Lett. 83, 3734 (2003); http://dx.doi.org/10.1063/1.1625113 (3 pages) | Cited 31 times

Online Publication Date: 28 October 2003

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We have used x-ray photoelectron spectroscopy with high energy resolution to determine band discontinuities at the two buried interfaces of the epitaxial TiO2 (anatase)/SrTiO3/Si(001) system. The valence band offsets are −2.1±0.1 eV and +0.2±0.1 eV at the SrTiO3/Si and TiO2/SrTiO3 heterojunctions, respectively. Assuming bulk band gaps for the SrTiO3 and TiO2 epitaxial films, the associated conduction band offsets are +0.1±0.1 eV and +0.1±0.1 eV. Si at the interface is in a flatband state, indicating a very low density of electronic states. These results suggest that spin-polarized electron injection from ferromagnetic Co-doped TiO2 anatase into Si should be facile. © 2003 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.Pq Other materials
79.60.Jv Interfaces; heterostructures; nanostructures
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.25.Mk Spin transport through interfaces
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