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10 May 1999

Volume 74, Issue 19, pp. 2737-2895

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Consistent time-of-flight mobility measurements and polymer light-emitting diode current–voltage characteristics

I. H. Campbell, D. L. Smith, C. J. Neef, and J. P. Ferraris

Appl. Phys. Lett. 74, 2809 (1999); http://dx.doi.org/10.1063/1.124021 (3 pages) | Cited 83 times

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We present time-of-flight mobility measurements and measured and calculated current–voltage (I–V) characteristics of structures fabricated using a soluble poly(p-phenylene vinylene) derivative. Time-of-flight measurements were used to determine the electric field dependent hole mobility. This mobility was then used, without adjustable parameters, to calculate the I–V characteristics of space-charge-limited, hole only devices. The measured and calculated I–V characteristics are in good agreement over five orders of magnitude in current. These results demonstrate that an electric field dependent mobility, without invoking trapping effects, provides an accurate description of hole transport in this polymer. © 1999 American Institute of Physics.
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85.60.Jb Light-emitting devices
73.50.Fq High-field and nonlinear effects
73.61.Ph Polymers; organic compounds
42.70.Jk Polymers and organics

Critical built-in electric field for an optimum carrier collection in multiquantum well p-i-n diodes

I. Serdiukova, C. Monier, M. F. Vilela, and A. Freundlich

Appl. Phys. Lett. 74, 2812 (1999); http://dx.doi.org/10.1063/1.124022 (3 pages) | Cited 11 times

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The collection efficiency of carrier photogenerated in the intrinsic region of strained InAsxP1−x/InP multiquantum well p-i-n structures is analyzed. The existence of a critical threshold built-in electric field value above which total carrier collection becomes possible is demonstrated. Maximized carrier collection and high output voltage are systematically reached for built-in electric field exceeding the critical value while similar structures operating with a substantially lower built-in electric field (e.g., identical well characteristics but thicker i region) yields nonoptimized collection of carrier in this area and altered voltage output. The slight dependence of the critical electric field with the carrier confinement level is revealed, stressing out the importance of thermally activated escape energy. Finally, the results are discussed in the context of photovoltaic devices showing substantial efficiency improvement for devices designed with built-in electric fields in excess of the threshold value. © 1999 American Institute of Physics.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.61.Ey III-V semiconductors
85.60.Dw Photodiodes; phototransistors; photoresistors
84.60.Jt Photoelectric conversion
73.50.Pz Photoconduction and photovoltaic effects

InAs/InGaAs quantum dot structures on GaAs substrates emitting at 1.3 μm

V. M. Ustinov, N. A. Maleev, A. E. Zhukov, A. R. Kovsh, A. Yu. Egorov, A. V. Lunev, B. V. Volovik, I. L. Krestnikov, Yu. G. Musikhin, N. A. Bert, P. S. Kop’ev, Zh. I. Alferov, N. N. Ledentsov, and D. Bimberg

Appl. Phys. Lett. 74, 2815 (1999); http://dx.doi.org/10.1063/1.124023 (3 pages) | Cited 164 times

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InAs self-organized quantum dots inserted in InGaAs quantum well have been grown on GaAs substrates by molecular beam epitaxy. The lateral size of the InAs islands has been found to be approximately 1.5 times larger as compared to the InAs/GaAs case, whereas the island heights and surface densities were close in both cases. The quantum dot emission wavelength can be controllably changed from 1.1 to 1.3 μm by varying the composition of the InGaAs quantum well matrix. Photoluminescence at 1.33 μm from vertical optical microcavities containing the InAs/InGaAs quantum dot array was demonstrated. © 1999 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Phonon-assisted capture and intradot Auger relaxation in quantum dots

R. Ferreira and G. Bastard

Appl. Phys. Lett. 74, 2818 (1999); http://dx.doi.org/10.1063/1.124024 (3 pages) | Cited 93 times

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We report on calculations of capture and relaxation of carriers in quantum dots, specifically, InAs/GaAs self-assembled dots. We point out that the phonon-assisted carrier capture presents strong resonances versus the dot size and that the intradot Auger relaxation is extremely fast in these structures. This shows that energy relaxation in InAs/GaAs self-organized quantum dots is dominated by capture effects. © 1999 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.55.Eq III-V semiconductors
63.20.K- Phonon interactions
71.38.-k Polarons and electron-phonon interactions

Nature and elimination of yellow-band luminescence and donor–acceptor emission of undoped GaN

G. Li, S. J. Chua, S. J. Xu, W. Wang, P. Li, B. Beaumont, and P. Gibart

Appl. Phys. Lett. 74, 2821 (1999); http://dx.doi.org/10.1063/1.124025 (3 pages) | Cited 36 times

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The nature of yellow-band luminescence (YL) and donor–acceptor (DA) emissions of undoped GaN grown on sapphire or laterally overgrown on patterned Si3N4 was investigated using low-temperature photoluminescence and spatially resolved photoluminescence. The states, producing the levels responsible for the YL and DA emissions, arise from complexes of extended defects and native-point defects (most likely Ga vacancies) or impurities (such as carbon). For GaN directly grown on a low-temperature-grown GaN buffer layer, the YL and DA emissions can be eliminated by simply increasing the buffer-layer growth temperature as the result of enlarging hexagonal crystallites, and consequently, reducing the density of extended defects. For laterally overgrown GaN, a much lower density of extended defects substantially suppresses the YL emission. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
71.55.Eq III-V semiconductors
61.72.Nn Stacking faults and other planar or extended defects
61.72.J- Point defects and defect clusters

Nanometer-scale studies of vertical organization and evolution of stacked self-assembled InAs/GaAs quantum dots

B. Lita, R. S. Goldman, J. D. Phillips, and P. K. Bhattacharya

Appl. Phys. Lett. 74, 2824 (1999); http://dx.doi.org/10.1063/1.124026 (3 pages) | Cited 48 times

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We have investigated the vertical organization and evolution of 1-, 5-, 10-, and 20-layer stacks of molecular beam epitaxially grown self-assembled InAs/GaAs quantum dots using high resolution and large-scale cross-sectional scanning tunneling microscopy. We report results regarding the evolution of the dot sizes and shapes, and the assembly of vertically organized columns of stacked dots. As the number of dot layers within a stack is increased, the average spacing between vertically organized columns decreases, and the corresponding dots become more uniform in size. The data also suggest that the coalescence of neighboring stacks of dots has not occurred and therefore coalescence is not the mechanism leading to the observed uniform distribution of dot sizes and column spacings. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Stability investigation of cubic GaN films grown by metalorganic chemical vapor deposition on GaAs (001)

X. L. Sun, Hui Yang, L. X. Zheng, D. P. Xu, J. B. Li, Y. T. Wang, G. H. Li, and Z. G. Wang

Appl. Phys. Lett. 74, 2827 (1999); http://dx.doi.org/10.1063/1.124027 (3 pages) | Cited 14 times

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The thermal stability of cubic-phase GaN (c-GaN) films are investigated by photoluminescence (PL) and Raman scattering spectroscopy. C-GaN films are grown on GaAs (001) substrates by metalorganic chemical vapor deposition. PL measurements show that the near-band-edge emissions in the as-grown GaN layers and thermally treated samples are mainly from c-GaN. No degradation of the optical qualities is observed after thermal annealing. Raman scattering spectroscopy shows that the intensity of the E2 peak from hexagonal GaN grains increases with annealing temperature for the samples with poor crystal quality, while thermal annealing up to 1000 °C has no obvious effect on the samples with high crystal quality. © 1999 American Institute of Physics.
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68.60.Dv Thermal stability; thermal effects
78.30.Fs III-V and II-VI semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Cc Kinetics of defect formation and annealing
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Deep levels in p-type InGaAsN lattice matched to GaAs

D. Kwon, R. J. Kaplar, S. A. Ringel, A. A. Allerman, Steven R. Kurtz, and E. D. Jones

Appl. Phys. Lett. 74, 2830 (1999); http://dx.doi.org/10.1063/1.124028 (3 pages) | Cited 45 times

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Deep-level transient spectroscopy measurements were utilized to investigate deep-level defects in metal–organic chemical vapor deposition-grown, unintentionally doped p-type InGaAsN films lattice matched to GaAs. The as-grown material displayed a high concentration of deep levels distributed within the band gap, with a dominant hole trap at Ev+0.10 eV. Postgrowth annealing simplified the deep-level spectra, enabling the identification of three distinct hole traps at 0.10, 0.23, and 0.48 eV above the valence-band edge, with concentrations of 3.5×1014, 3.8×1014, and 8.2×1014 cm−3, respectively. A direct comparison between the as-grown and annealed spectra revealed the presence of an additional midgap hole trap, with a concentration of 4×1014 cm−3 in the as-grown material. The concentration of this trap is sharply reduced by annealing, which correlates with improved material quality and minority-carrier properties after annealing. Of the four hole traps detected, only the 0.48 eV level is not influenced by annealing, suggesting this level may be important for processed InGaAsN devices in the future. © 1999 American Institute of Physics.
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71.55.Eq III-V semiconductors
73.61.Ey III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
61.72.Cc Kinetics of defect formation and annealing
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Ea III-V semiconductors

Deposition of passivated gold nanoclusters onto prepatterned substrates

A. J. Parker, P. A. Childs, R. E. Palmer, and M. Brust

Appl. Phys. Lett. 74, 2833 (1999); http://dx.doi.org/10.1063/1.124029 (3 pages) | Cited 13 times

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Gold nanoclusters, chemically passivated with decanethiol, have been deposited from solution onto silicon dioxide surfaces prepatterned by photolithography. After lift-off of the photoresist, preferential cluster accumulation is observed along the edges of the resist structures. Elsewhere on the hydrophilic surface, islands of clusters are observed. By contrast, HF treatment, creating a hydrophobic surface, leads to wetting of the unmasked regions of the substrate by the passivated clusters. © 1999 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.05.Bx Metals, semimetals, and alloys
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.55.-a Thin film structure and morphology
85.40.Hp Lithography, masks and pattern transfer
81.65.Rv Passivation

Epitaxial lateral overgrowth of GaN over AlOx surface formed on Si substrate

Nobuhiko P. Kobayashi, Junko T. Kobayashi, Xingang Zhang, P. Daniel Dapkus, and Daniel H. Rich

Appl. Phys. Lett. 74, 2836 (1999); http://dx.doi.org/10.1063/1.124030 (3 pages) | Cited 26 times

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An approach by which single crystal α-GaN can be grown laterally over oxidized AlAs (AlOx) formed on Si substrates is demonstrated. Regular α-Ga2-O3 stripe templates, spatially separated by AlOx, on which subsequent GaN growth is selectively seeded are formed. Since the boundary between the stripe template and AlOx is nominally planar, two pyramidal planes on separated GaN can merge by growing laterally over the AlOx (referred to as planar epitaxial lateral overgrowth). Transmission electron microscopy reveals that the number of structural defects in GaN laterally grown over the AlOx is remarkably reduced compared to that in GaN grown on the stripe templates, and accordingly cathodoluminescence reveals a strong band edge emission from GaN laterally grown over the AlOx, suggesting that this approach allows us to grow GaN on Si substrates with fewer defects. © 1999 American Institute of Physics.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.60.Hk Cathodoluminescence, ionoluminescence
81.05.Ea III-V semiconductors
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