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9 Oct 2000

Volume 77, Issue 15, pp. 2271-2423

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Vertically faceted lateral overgrowth of GaN on SiC with conducting buffer layers using pulsed metalorganic chemical vapor deposition

R. S. Qhalid Fareed, J. W. Yang, Jianping Zhang, Vinod Adivarahan, Vinamra Chaturvedi, and M. Asif Khan

Appl. Phys. Lett. 77, 2343 (2000); http://dx.doi.org/10.1063/1.1316063 (3 pages) | Cited 26 times

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A “pulsed metalorganic chemical vapor deposition” technique has been developed for lateral overgrowth of GaN thin films on SiC with conducting buffer layers for vertically conducting devices. Growth was carried out at temperatures as low as 950 °C keeping a constant gallium flux while pulsing NH3. We demonstrate that, by varying the NH3 pulse duration, growth morphology can be gradually changed from triangular to rectangular for the lateral overgrowth. Even at a V/III ratio as low as 550, high quality smooth layers with (1100) vertical facets were successfully grown with a lateral to vertical growth rate ratio as high as 4:1. Atomic force microscopic measurements show the root-mean-square roughness of the laterally overgrown layers to be 7.0 Å. Scanning thermal microscopy was used to measure a thermal conductivity of 1.7 and 1.5 W/cm K, respectively, for the laterally overgrown film and the GaN deposition in the window region. © 2000 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Ea III-V semiconductors
68.55.-a Thin film structure and morphology
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
68.35.B- Structure of clean surfaces (and surface reconstruction)

Monte Carlo study of spin relaxation in AlGaAs/GaAs quantum wells

A. Bournel, P. Dollfus, E. Cassan, and P. Hesto

Appl. Phys. Lett. 77, 2346 (2000); http://dx.doi.org/10.1063/1.1316771 (3 pages) | Cited 14 times

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An original approach is developed to investigate the electron spin dynamics in III–V quantum wells using a particle Monte Carlo transport model. We study the spin precession related to the D’yakonov–Perel’ mechanism, which is believed to be the predominant spin relaxation phenomenon in AlGaAs/GaAs quantum wells at room temperature. Using a Monte Carlo approach, the effect of electron/crystal scatterings on the D’yakonov–Perel’ mechanism can be both simply and accurately taken into account. Finally, including interface roughness in the calculation leads to spin relaxation times in good agreement with the experimental data. © 2000 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
63.20.K- Phonon interactions
71.38.-k Polarons and electron-phonon interactions
68.35.Ct Interface structure and roughness

Investigation of deep electronic centers in low-temperature grown GaAs using extremely thin layers

K.-F. G. Pfeiffer, S. Tautz, P. Kiesel, C. Steen, S. Malzer, and G. H. Döhler

Appl. Phys. Lett. 77, 2349 (2000); http://dx.doi.org/10.1063/1.1316078 (3 pages) | Cited 3 times

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We report on an approach to investigate the deep electronic defect centers in low-temperature grown GaAs (LT-GaAs). Using an extremely thin LT-GaAs layer (comparable with the penetration depth of an electric field in bulk material) incorporated in the i layer of a p-i-n diode, we are able to charge or to deplete the deep centers in the energy gap by applying a reverse bias. The corresponding space charge is monitored by the field changes across the LT-GaAs layer, both optically by Franz–Keldysh experiments and electrically by n-channel conductance changes. From our results, we derive a deep trap density of 1018 cm−3 centered at around 500–700 meV below the conduction band. © 2000 American Institute of Physics.
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71.55.Eq III-V semiconductors
73.61.Ey III-V semiconductors
85.30.Kk Junction diodes
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Dominant role of surface states in photoexcited carrier dynamics in CdSe nanocrystalline films prepared by chemical deposition

P. Malý, J. Kudrna, F. Trojánek, D. Mikeš, P. Němec, A. C. Maciel, and J. F. Ryan

Appl. Phys. Lett. 77, 2352 (2000); http://dx.doi.org/10.1063/1.1317536 (3 pages) | Cited 6 times

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We report on ultrafast carrier dynamics in nanocrystalline CdSe thin films prepared by chemical solution deposition. The photoluminescence and transient absorption dynamics have spectrally dependent decay faster at shorter wavelengths. The spectral behavior of the decay rates in samples with different nanocrystal sizes and the sensitivity of the dynamics on the surface modification indicate the dominant role of the surface states in the photoluminescence. © 2000 American Institute of Physics.
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78.66.Hf II-VI semiconductors
73.20.At Surface states, band structure, electron density of states
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.55.Et II-VI semiconductors
78.40.Fy Semiconductors
78.66.Vs Fine-particle systems
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
73.22.-f Electronic structure of nanoscale materials and related systems
81.07.-b Nanoscale materials and structures: fabrication and characterization

Spin-dependent Coulomb blockade in a silicon-on-insulator-based single-electron transistor

S. D. Lee, K. S. Park, J. W. Park, Y. M. Moon, Jung B. Choi, K.-H. Yoo, and J. Kim

Appl. Phys. Lett. 77, 2355 (2000); http://dx.doi.org/10.1063/1.1317540 (3 pages) | Cited 7 times

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We report low-temperature conductance measurement on a Coulomb-blockaded dot in a silicon-on-insulator-based single-electron transistor with in-plane side gates. The linear conductance for 4.2 K at zero magnetic field exhibits up to three paired peaks, indicating simple alternating odd (spin 1/2)-even(spin 0) filling. Three intrapair spacings are found to be nearly a constant value, corresponding to the single charging energy U, whereas two interpair spacings are different which are associated with U+ΔE1 and U+ΔE2, i.e., successive quantized level spacings added to U. The quantized level spacings were also revealed in the nonlinear current staircases. © 2000 American Institute of Physics.
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85.35.Gv Single electron devices
85.35.Ds Quantum interference devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.23.Hk Coulomb blockade; single-electron tunneling
85.30.De Semiconductor-device characterization, design, and modeling

Approach to enhance deuterium incorporation for improved hot carrier reliability in metal-oxide-semiconductor devices

Kangguo Cheng, Jinju Lee, and Joseph W. Lyding

Appl. Phys. Lett. 77, 2358 (2000); http://dx.doi.org/10.1063/1.1317546 (3 pages) | Cited 12 times

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The deuterium isotope effect has been widely demonstrated to improve hot-carrier reliability in metal-oxide-semiconductor transistors. Most of the interface traps, however, may have been passivated by hydrogen before the final deuterium anneal due to the ubiquitous presence of hydrogen in modern complementary metal-oxide-semiconductor processing technology. Therefore, effective deuteration requires both deuterium diffusion to the SiO2–Si interface and displacement of the previously bonded hydrogen. We have introduced a “prestress” process in which hydrogen is depassivated before deuterium annealing. We found that the prestressed transistors are more robust to hot-carrier stress than control transistors without the prestress. We have also found that the replacement of hydrogen with deuterium is the rate-limiting step for deuterium incorporation at the SiO2–Si interface. With the prestress, a lower deuterium annealing temperature can be applied without compromising the reliability improvement. © 2000 American Institute of Physics.
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85.30.Tv Field effect devices
81.65.Rv Passivation
61.72.Cc Kinetics of defect formation and annealing

Meyer–Neldel rule in amorphous strontium titanate thin films

K. Morii, T. Matsui, H. Tsuda, and H. Mabuchi

Appl. Phys. Lett. 77, 2361 (2000); http://dx.doi.org/10.1063/1.1317543 (3 pages) | Cited 10 times

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In this letter, we report the experimental result indicating that the electrical conductivity in thin films of amorphous strontium titanate (a-STO) is well fit to the Meyer–Neldel (MN) rule over the temperature range 300–470 K. The films were ion-beam sputtered and annealed in two different atmospheres: a vacuum and flowing oxygen. The MN plots for the films show two parallel straight lines depending on the annealing atmosphere, which give the identical MN parameters of about 35 meV with the conductivity prefactors of 9.3×10−10 and 2.3×10−14(Ω cm)−1 for the vacuum- and oxygen- annealed films, respectively. © 2000 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
73.61.-r Electrical properties of specific thin films

Effects of boundary roughness on the conductance of quantum wires

D. Csontos and H. Q. Xu

Appl. Phys. Lett. 77, 2364 (2000); http://dx.doi.org/10.1063/1.1311606 (3 pages) | Cited 13 times

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The generic effects induced by boundary roughness on the electron transport through quantum wires have been studied. It is found that the conductance of the rough quantum wires shows rapid fluctuations and strong, broad dips between adjacent plateaus at very low temperatures, and a recovery of the plateau structure at increased temperatures. It is also found that in the recovered plateau structure, the step values are suppressed and the conductance shows long transition regions between adjacent steps. These results agree with existing experiments and can be used as a guideline for the evaluation of the fabrication process of quantum wires. © 2000 American Institute of Physics.
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73.61.-r Electrical properties of specific thin films
68.35.Ct Interface structure and roughness
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Highly stable dye-sensitized solid-state solar cell with the semiconductor 4CuBr 3S(C4H9)2 as the hole collector

K. Tennakone, G. K. R. Senadeera, D. B. R. A. De Silva, and I. R. M. Kottegoda

Appl. Phys. Lett. 77, 2367 (2000); http://dx.doi.org/10.1063/1.1312858 (3 pages) | Cited 26 times

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Construction of a dye-sensitized solid-state solar cell with the semiconductor 4CuBr 3S(C4H9)2 as the hole collector is reported. The cell is unusually stable compared to dye-sensitized solid state cells reported previously and delivers a short-circuit photocurrent and an open-circuit voltage of ∼4.3 mA cm−2 and 400 mV respectively, at 1.5 air mass, 1000 W m−2 sunlight. © 2000 American Institute of Physics.
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84.60.Jt Photoelectric conversion
73.61.Ph Polymers; organic compounds
73.50.Pz Photoconduction and photovoltaic effects
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