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1 Nov 2004

Volume 85, Issue 18, pp. 3959-4247

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 4142 (2004); http://dx.doi.org/10.1063/1.1811774 (3 pages)

Hong Jin Fan, Roland Scholz, Florian M. Kolb, and Margit Zacharias
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Elliptically polarized pump-probe spectroscopy and its application to observation of electron-spin relaxation in GaAs quantum wells

Tianshu Lai, Luning Liu, Qian Shou, Liang Lei, and Weizhu Lin

Appl. Phys. Lett. 85, 4040 (2004); http://dx.doi.org/10.1063/1.1811794 (3 pages) | Cited 8 times

Online Publication Date: 3 November 2004

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An elliptically polarized pump-probe spectroscopy is developed. A theoretical model is derived from the rate equations of two-level system with small signal approximation to describe the experimental signal of the spectroscopy. The spectroscopy eliminates the systematic errors between theories and experimental results in present circularly polarized pump-probe spectroscopy, and is implemented easily in experiments. The initial degree of spin polarization of carriers in an excited state can be extracted by means of the spectroscopy, which is an important parameter in the investigation of spatial transport of spin polarization. The electron-spin relaxation in GaAs quantum wells is studied by using this spectroscopy.
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73.63.Hs Quantum wells
72.25.Dc Spin polarized transport in semiconductors

Extremely high electron mobility of pseudomorphic In0.74Ga0.26As∕In0.46Al0.54As modulation-doped quantum wells grown on (411)A InP substrates by molecular-beam epitaxy

T. Kitada, T. Aoki, I. Watanabe, S. Shimomura, and S. Hiyamizu

Appl. Phys. Lett. 85, 4043 (2004); http://dx.doi.org/10.1063/1.1807023 (3 pages) | Cited 4 times

Online Publication Date: 3 November 2004

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Much enhanced electron mobility of 105 000 cm2∕V s with a high sheet electron concentration (Ns) of 3.1×1012 cm−12 was obtained at 77 K in pseudomorphic In0.74Ga0.26As∕In0.46Al0.54As modulation-doped quantum well (MD-QW) grown on a (411)A InP substrate by molecular-beam epitaxy. This MD-QW has the “(411)A super-flat interfaces” (effectively atomically flat interfaces over a wafer-size area), which leads to significant reduction of interface roughness scattering at low temperatures. The highest electron mobility of the (411)A MD-QW was achieved by using pseudomorphic In0.46Al0.54As barriers. The electron mobility is 44% higher than that (73 000 cm2∕V s at 77 K) of a similar MD-QW structure grown on a conventional (100)InP substrate.
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81.07.St Quantum wells
81.05.Ea III-V semiconductors
73.63.Hs Quantum wells
68.65.Fg Quantum wells
73.50.Fq High-field and nonlinear effects
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Charge carrier transport in an emissive layer of green electrophosphorescent devices

Noriyuki Matsusue, Satoshi Ikame, Yuichiro Suzuki, and Hiroyoshi Naito

Appl. Phys. Lett. 85, 4046 (2004); http://dx.doi.org/10.1063/1.1813628 (3 pages) | Cited 36 times

Online Publication Date: 3 November 2004

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Charge carrier generation and transport in fac tris (2-phenylpyridine) iridium (III) (Ir(ppy)3) doped in 4,4′-N,N′-dicarbazole-biphenel (CBP) thin films have been studied in terms of time-of-flight and time-resolved photoluminescence spectroscopies. It is found that the excitation energy rapidly transfer from CBP to Ir(ppy)3, and that the charge carriers are generated on Ir(ppy)3 sites. With increasing Ir(ppy)3 concentration, the electron drift mobility is slightly decreased, while the hole transit signals become unobservable. The electron and hole transport properties of Ir(ppy)3 doped CBP thin films result from the energy levels of the lowest unoccupied molecular orbital and the highest occupied molecular orbital of Ir(ppy)3 with respect to those of CBP.
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85.60.Jb Light-emitting devices
78.66.Qn Polymers; organic compounds
73.50.Dn Low-field transport and mobility; piezoresistance
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.47.-p Spectroscopy of solid state dynamics
78.55.Kz Solid organic materials

Spectroscopic second harmonic generation measured on plasma-deposited hydrogenated amorphous silicon thin films

W. M. M. Kessels, J. J. H. Gielis, I. M. P. Aarts, C. M. Leewis, and M. C. M. van de Sanden

Appl. Phys. Lett. 85, 4049 (2004); http://dx.doi.org/10.1063/1.1812836 (3 pages) | Cited 9 times

Online Publication Date: 3 November 2004

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Optical second harmonic generation (SHG) has been measured for plasma-deposited thin films of hydrogenated amorphous silicon (a‐Si:H) at different polarization states for pump photon energies between 1.0 and 1.7 eV. Distinct resonance peaks are observed in this energy range and it is shown that the SH signal originates from an isotropic contribution at both the film-surface and substrate-interface region. The possibility that the SH signal originates from surface and interface dangling bond states of a‐Si:H is discussed.
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81.05.Cy Elemental semiconductors
68.55.-a Thin film structure and morphology
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
71.55.Cn Elemental semiconductors
73.20.At Surface states, band structure, electron density of states
78.66.Jg Amorphous semiconductors; glasses
78.66.Db Elemental semiconductors and insulators

Hydrogen plasma enhancement of boron activation in shallow junctions

A. Vengurlekar, S. Ashok, C. E. Kalnas, and N. D. Theodore

Appl. Phys. Lett. 85, 4052 (2004); http://dx.doi.org/10.1063/1.1811394 (3 pages) | Cited 2 times

Online Publication Date: 3 November 2004

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The ability to activate large concentrations of boron at lower temperatures is a persistent contingency in the continual drive for device scaling in Si microelectronics. We report on our experimental observations offering evidence for enhancement of electrical activation of implanted boron dopant in the presence of atomic hydrogen in silicon. This increased electrical activity of boron at lower anneal temperature is attributed to the creation of vacancies in the boron-implanted region, lattice-relaxation caused by the presence of atomic hydrogen, and the effect of atomic hydrogen on boron-interstitial cluster formation.
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61.72.uf Ge and Si
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

A Raman scattering-based method to probe the carrier drift velocity in semiconductors: Application to gallium nitride

A. V. Andrade-Neto, A. R. Vasconcellos, R. Luzzi, and V. N. Freire

Appl. Phys. Lett. 85, 4055 (2004); http://dx.doi.org/10.1063/1.1808231 (3 pages) | Cited 4 times

Online Publication Date: 3 November 2004

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A single expression relating the carrier drift velocity in semiconductors under an electric field to Raman scattering data is derived resorting to a full nonequilibrium picture for electrons and holes. It allows one to probe with high optical precision both the ultrafast transient as well as the steady state carriers' drift velocity in semiconductor systems. This is achieved by simply modifying the experimental geometry, thus changing the angle between the transferred wave vector Q and the applied electric field E, and measuring the frequency shift promoted by the presence of the field to be observed in the single-particle and plasmon scattering spectra. An application to zinc-blende gallium nitride is presented to highlight the power of the method.
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78.30.Fs III-V and II-VI semiconductors
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
72.20.Fr Low-field transport and mobility; piezoresistance

Thermal stability of electron traps in GaN grown by metalorganic chemical vapor deposition

D. Johnstone, S. Doğan, J. Leach, Y. T. Moon, Y. Fu, Y. Hu, and H. Morkoç

Appl. Phys. Lett. 85, 4058 (2004); http://dx.doi.org/10.1063/1.1814801 (3 pages) | Cited 6 times

Online Publication Date: 3 November 2004

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Deep level transient spectroscopy was used to investigate the thermal stability of electron traps in n-type GaN grown by metalorganic chemical vapor deposition. The concentration of traps at 160 and at 500 K increased more than fivefold over the course of several 700 K anneal cycles, while a peak at 320 K increased by a factor of only 1.19. The increase in the trap concentration with repeated annealing might be due to a mobile trap or loss of passivant. Hydrogen is very likely present in high concentration in the epilayer, and its passivating effects may be lost with annealing.
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68.55.A- Nucleation and growth
73.61.Ey III-V semiconductors
65.40.-b Thermal properties of crystalline solids
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
81.40.Gh Other heat and thermomechanical treatments
81.65.Rv Passivation

Recombination activity of interstitial iron and other transition metal point defects in p- and n-type crystalline silicon

Daniel Macdonald and L. J. Geerligs

Appl. Phys. Lett. 85, 4061 (2004); http://dx.doi.org/10.1063/1.1812833 (3 pages) | Cited 56 times

Online Publication Date: 3 November 2004

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Interstitial iron in crystalline silicon has a much larger capture cross section for electrons than holes. According to the Shockley–Read–Hall model, the low-injection carrier lifetime in p-type silicon should therefore be much lower that in n-type silicon, while in high injection they should be equal. In this work we confirm this modeling using purposely iron-contaminated samples. A survey of other transition metal impurities in silicon reveals that those which tend to occupy interstitial sites at room temperature also have significantly larger capture cross sections for electrons. Since these are also the most probable metal point defects to occur during high temperature processing, using n-type wafers for devices such as solar cells may offer greater immunity to the effects of metal contaminants.
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81.05.Cy Elemental semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
61.72.J- Point defects and defect clusters
61.72.uf Ge and Si
61.72.S- Impurities in crystals

Critical point energy as a function of electric field determined by electroreflectance of surface-intrinsic-n+ type doped GaAs

Y. S. Chen, K. S. Wu, D. P. Wang, K. F. Huang, and T. C. Huang

Appl. Phys. Lett. 85, 4064 (2004); http://dx.doi.org/10.1063/1.1814794 (3 pages)

Online Publication Date: 3 November 2004

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Electroreflectance of surface-intrinsic-n+ type doped GaAs has been measured over a various biased voltage. The spectra have exhibited many Franz–Keldysh oscillations (FKOs) above band gap energy Eg. The electric field F and critical point energy Ec can be determined from the slope and intercept of FKOs fitting. Hence, we can obtain Ec as a function of F. In most of previous works, Ec is taken as Eg. However, it was found that Ec increases with F in this work. In order to explain this, the gain of energy of electron and hole in F was discussed.
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78.20.Jq Electro-optical effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Properties of highly Cr-doped AlN

A. Y. Polyakov, N. B. Smirnov, A. V. Govorkov, R. M. Frazier, J. Y. Liefer, G. T. Thaler, C. R. Abernathy, S. J. Pearton, and J. M. Zavada

Appl. Phys. Lett. 85, 4067 (2004); http://dx.doi.org/10.1063/1.1812845 (3 pages) | Cited 21 times

Online Publication Date: 3 November 2004

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Cr concentrations of ∼2 at. % were incorporated into AlN during growth by molecular beam epitaxy. Under optimized conditions, single-phase, insulating AlCrN is produced whose band gap shows a small (0.1–0.2 eV) decrease from the value for undoped AlN (6.2 eV), a decrease in a-plane lattice constant and the introduction of two absorption bands at 3 and 5 eV into the band gap. This material shows ferromagnetism with a Curie temperature above 300 K as judged from the difference in field-cooled and zero-field-cooled magnetization. For nonoptimized growth, second phases of Cr2N and AlxCry are produced in the AlN and the material is conducting (∼1000 Ω cm) with activation energy for conduction of 0.19 eV and apparent band gap of 5.8 eV.
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81.05.Ea III-V semiconductors
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
75.70.Ak Magnetic properties of monolayers and thin films
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
78.60.Hk Cathodoluminescence, ionoluminescence
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.S- Impurities in crystals
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

p-type ZnO films by monodoping of nitrogen and ZnO-based p–n homojunctions

J. M. Bian, X. M. Li, C. Y. Zhang, W. D. Yu, and X. D. Gao

Appl. Phys. Lett. 85, 4070 (2004); http://dx.doi.org/10.1063/1.1808229 (3 pages) | Cited 51 times

Online Publication Date: 3 November 2004

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Nitrogen-doped p-type ZnO (ZnO:N) films have been achieved by ultrasonic spray pyrolysis at atmosphere. The high structural quality of the obtained films was confirmed by x-ray diffraction, scanning electron microscopy, and photoluminescence spectra. Hall-effect and Seebeck-effect measurements indicate that the obtained p-type ZnO film shows a low resistivity of 3.02×10−2 Ω cm, high carrier concentration of 8.59×1018 cm−3, high mobility of 24.1 cm2∕V s, and high Seebeck coefficient of 408.2 μV∕K at room temperature. Furthermore, the two-layer structured ZnO p–n homojunctions were prepared by depositing n-type ZnO layer on p-type ZnO:N layer. The current–voltage curve derived from the two-layer structure clearly shows the typical rectifying characteristic of p–n junctions.
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81.05.Dz II-VI semiconductors
68.55.A- Nucleation and growth
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.uj III-V and II-VI semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.20.My Galvanomagnetic and other magnetotransport effects
72.20.Pa Thermoelectric and thermomagnetic effects
73.50.Lw Thermoelectric effects
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Ga II-VI semiconductors
78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
81.15.Rs Spray coating techniques
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
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