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26 May 2003

Volume 82, Issue 21, pp. 3587-3793

Issue Cover Spotlight Figure

Appl. Phys. Lett. 82, 3716 (2003); http://dx.doi.org/10.1063/1.1577808 (3 pages)

V. Novosad, M. Grimsditch, J. Darrouzet, J. Pearson, S. D. Bader, V. Metlushko, K. Guslienko, Y. Otani, H. Shima, and K. Fukamichi
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Ultrafast carrier and plasmon-phonon dynamics in ion-irradiated n-GaAs

Muneaki Hase, Kunie Ishioka, Masahiro Kitajima, and Kiminori Ushida

Appl. Phys. Lett. 82, 3668 (2003); http://dx.doi.org/10.1063/1.1578179 (3 pages) | Cited 12 times

Online Publication Date: 20 May 2003

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Ultrafast dynamics of plasmon-phonon coupled modes and photoexcited carriers in He ion irradiated n-GaAs has been investigated with a femtosecond pump-probe technique. The frequencies of the coupled modes shift as the ion dose increases, and after 1.9×1013 He+/cm2 irradiation the coherent oscillation of the coupled modes disappear. The relaxation time of the photoexcited carriers decreases with increasing ion dose, which is explained quantitatively by trapping of carriers via the deep levels related to single vacancies. The dose dependence of the dephasing time of the coupled modes and the relaxation time of the photoexcited carriers reveal that the trapping of the majority carriers dominates the disappearance as well as the frequency shift of the coupled mode oscillation. © 2003 American Institute of Physics.
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71.55.Eq III-V semiconductors
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors

Deep level defect in Si-implanted GaN n+-p junction

X. D. Chen, Y. Huang, S. Fung, C. D. Beling, C. C. Ling, J. K. Sheu, M. L. Lee, G. C. Chi, and S. J. Chang

Appl. Phys. Lett. 82, 3671 (2003); http://dx.doi.org/10.1063/1.1578167 (3 pages) | Cited 6 times

Online Publication Date: 20 May 2003

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A deep level transient spectroscopy (DLTS) study has been performed on a GaN n+-p junction fabricated by implanting Si into a Mg-doped p-type GaN epilayer. A high concentration of a deep level defect has been revealed within the interfacial region of the junctions by the unusual appearance of a minority peak in the majority carrier DLTS spectra. The deep level defect appears to be an electron trap at EC-0.59 eV in the p-side region of the junction and has tentatively been attributed to the VN–Mg complex. The high concentration of this electrically active deep level defect in the depletion layer of the Si-implanted GaN n+-p junction diodes suggests the need for further investigations. © 2003 American Institute of Physics.
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73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
61.72.Yx Interaction between different crystal defects; gettering effect

Direction-dependent band nonparabolicity effects on high-field transient electron transport in GaN

M. Wraback, H. Shen, S. Rudin, E. Bellotti, M. Goano, J. C. Carrano, C. J. Collins, J. C. Campbell, and R. D. Dupuis

Appl. Phys. Lett. 82, 3674 (2003); http://dx.doi.org/10.1063/1.1577833 (3 pages) | Cited 15 times

Online Publication Date: 20 May 2003

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Time-resolved electroabsorption measurements on an AlGaN/GaN heterojunction p–i–n diode provide evidence of electron velocity overshoot at fields as low as ∼130 kV/cm for transport in the c-direction of wurtzite GaN. Theoretical Monte Carlo calculations employing a full band structure indicate that at fields below ∼300 kV/cm, this velocity overshoot is associated primarily with band nonparabolicity in the Γ valley related to a negative electron effective mass rather than intervalley transfer. Similar calculations of transport in the basal plane indicate that in this case, both a higher threshold field for velocity overshoot and a lower steady-state velocity at a given field are expected. © 2003 American Institute of Physics.
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85.60.Dw Photodiodes; phototransistors; photoresistors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.20.At Surface states, band structure, electron density of states
72.20.Ht High-field and nonlinear effects
78.20.Jq Electro-optical effects
78.47.-p Spectroscopy of solid state dynamics
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Interface defects responsible for negative-bias temperature instability in plasma-nitrided SiON/Si(100) systems

Shinji Fujieda, Yoshinao Miura, Motofumi Saitoh, Eiji Hasegawa, Shin Koyama, and Koichi Ando

Appl. Phys. Lett. 82, 3677 (2003); http://dx.doi.org/10.1063/1.1578535 (3 pages) | Cited 21 times

Online Publication Date: 20 May 2003

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Interface defects generated by negative-bias temperature stress (NBTS) in an ultrathin plasma- nitrided SiON/Si(100) system were characterized by using D2 annealing, conductance-frequency measurements, and electron-spin resonance measurements. D2 annealing was shown to lower negative-bias temperature instability (NBTI) than H2 annealing. Interfacial Si dangling bonds (Pb1 and Pb0 centers), whose density is comparable to an increase in interface trap density, were detected in a NBTS-stressed sample. The NBTI of the plasma-nitrided SiON/Si system was thus shown to occur through Pb depassivation. Furthermore, the nitridation was shown to increase the Pb1/Pb0 density ratio and modify the Pb1 structure. Such a predominance and structural modification of Pb1 centers are presumed to increase NBTI by enhancing the Pb–H dissociation. Although we suggest that NBTS may also induce non-Pb defects, nitrogen dangling bonds do not seem to be included in them. © 2003 American Institute of Physics.
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73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
76.30.Mi Color centers and other defects
61.72.Cc Kinetics of defect formation and annealing
52.77.Bn Etching and cleaning

Cathodoluminescence studies of the electron injection-induced effects in GaN

Leonid Chernyak, William Burdett, Mikhail Klimov, and Andrei Osinsky

Appl. Phys. Lett. 82, 3680 (2003); http://dx.doi.org/10.1063/1.1578514 (3 pages) | Cited 7 times

Online Publication Date: 20 May 2003

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Local irradiation of p-type GaN with the electron beam of a scanning electron microscope resulted in up to a threefold decrease of the peak cathodoluminescence intensity at ∼379 nm, as was observed in the variable temperature measurements. The cathodoluminescence results are consistent with an increase of the minority carrier diffusion length in the material, as is evident from the electron-beam-induced current measurements. The activation energy for the electron injection effect, estimated from the temperature-dependent cathodoluminescence, is in agreement with the thermal ionization energy of the Mg-acceptor in GaN. © 2003 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.55.Eq III-V semiconductors
72.80.Ey III-V and II-VI semiconductors

Metalorganic chemical vapor deposition of highly conductive Al0.65Ga0.35N films

P. Cantu, S. Keller, U. K. Mishra, and S. P. DenBaars

Appl. Phys. Lett. 82, 3683 (2003); http://dx.doi.org/10.1063/1.1577410 (3 pages) | Cited 16 times

Online Publication Date: 20 May 2003

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Highly conductive Al0.65Ga0.35N films were fabricated using indium–silicon codoping and a low growth temperature of 920 °C in the metalorganic chemical vapor deposition process. The Al0.65Ga0.35N:(Si,In) layers exhibited an n-type carrier density as high as 2.5×1019 cm−3 with an electron mobility of 22 cm2/V s, corresponding to a resistivity of 1.1×10−4 Ω cm. Significantly higher resistivity values were measured for AlxGa1−xN:Si doped films with x⩾0.49 deposited at 1150 °C without indium, e.g., the Al0.62Ga0.38N:Si samples exhibited a maximum carrier concentration of 1.3×1017 cm−3 and a resistivity of 6.2×10−2 Ω cm. The electrical properties of the films are discussed in relation to the chemical concentrations of silicon and residual impurities in the films. © 2003 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.61.Ey III-V semiconductors
81.05.Ea III-V semiconductors
61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Electron spin relaxation under drift in GaAs

E. A. Barry, A. A. Kiselev, and K. W. Kim

Appl. Phys. Lett. 82, 3686 (2003); http://dx.doi.org/10.1063/1.1578180 (3 pages) | Cited 22 times

Online Publication Date: 20 May 2003

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Based on a Monte Carlo method, we investigate the influence of transport conditions on the electron spin relaxation in GaAs. The decay of initial electron spin polarization is calculated as a function of distance under the presence of moderate drift fields and/or nonzero injection energies. For relatively low fields (a couple of kV/cm), a substantial amount of spin polarization is preserved for several microns at 300 K. However, it is also found that the spin relaxation rate increases rapidly with the drift field, scaling as the square of the electron wave vector in the direction of the field. When the electrons are injected with a high energy, a pronounced decrease is observed in the spin relaxation length due to an initial increase in the spin precession frequency. Hence, high-field or high-energy transport conditions may not be desirable for spin-based devices. © 2003 American Institute of Physics.
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75.47.Pq Other materials
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Ey III-V and II-VI semiconductors

Doping-induced strain in N-doped 4H–SiC crystals

H. Jacobson, J. Birch, C. Hallin, A. Henry, R. Yakimova, T. Tuomi, E. Janzén, and U. Lindefelt

Appl. Phys. Lett. 82, 3689 (2003); http://dx.doi.org/10.1063/1.1579120 (3 pages) | Cited 11 times

Online Publication Date: 20 May 2003

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Stress in epitaxial layers due to crystal lattice mismatch directly influences the growth, structure, and basic electrophysical parameters of epitaxial films and also to a large extent the degradation processes in semiconductor devices. In this letter, we present a theoretical model for calculating the induced lattice compression due to N doping and the critical thickness concerning formation of misfit dislocations in homoepitaxial 4H–SiC layers with different N-doping levels. For example: The model predicts that substrates with a N concentration of 3×1019 cm−3 induce misfit dislocations when the epilayer thickness reaches ∼ 10 μm. Also, the N-doping concentration in the 1×1018–1×1019 cm−3 range yields a strain that not will cause misfit dislocactions at the substrate and epilayer interface until an epilayer thickness of 200–300 μm is reached. Supporting evidence of the induced lattice compression due to N doping have been done by synchrotron white-beam x-ray topography on samples with different N-doping levels and are compared with the predicted results from the model. © 2003 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
68.55.-a Thin film structure and morphology
61.72.S- Impurities in crystals
62.20.-x Mechanical properties of solids

Nitride microlens arrays for blue and ultraviolet wavelength applications

T. N. Oder, J. Shakya, J. Y. Lin, and H. X. Jiang

Appl. Phys. Lett. 82, 3692 (2003); http://dx.doi.org/10.1063/1.1579872 (3 pages) | Cited 22 times

Online Publication Date: 20 May 2003

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Nitride microlens arrays with sizes as small as 10 μm in diameter have been fabricated on GaN and AlN epilayers using the method of photoresist reflow and inductively coupled plasma dry etching. The focal lengths of the microlenses varied from 7–30 μm as determined by theoretical fitting as well as by the near-field scanning optical microscopy measurement. Scanning electron and atomic force microscopies were used to obtain the surface profile of the microlenses which were found to match very well with hemispherical fitting and a surface roughness value around 1 nm was obtained. Nitride microlens arrays would be naturally chosen for green/blue to deep ultraviolet wavelength applications. In addition, nitride microlenses offer the possibility of integrating nitride-based microsize photonic devices as well as of coupling light into, out of, and between arrays of III-nitride emitters for other applications, such as spatially resolved fluorescence spectroscopy studies of biological and medical systems and optical links, thereby further expanding the applications of III nitrides. © 2003 American Institute of Physics.
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42.79.Bh Lenses, prisms and mirrors
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