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30 May 2005

Volume 86, Issue 22, Articles (22xxxx)

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Appl. Phys. Lett. 86, 223902 (2005); http://dx.doi.org/10.1063/1.1938253 (3 pages)

Philip J. Lee, Paul J. Hung, Robin Shaw, Lily Jan, and Luke P. Lee
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p-ZnO/n-GaN heterostructure ZnO light-emitting diodes

Dae-Kue Hwang, Soon-Hyung Kang, Jae-Hong Lim, Eun-Jeong Yang, Jin-Yong Oh, Jin-Ho Yang, and Seong-Ju Park

Appl. Phys. Lett. 86, 222101 (2005); http://dx.doi.org/10.1063/1.1940736 (3 pages) | Cited 130 times

Online Publication Date: 24 May 2005

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We report on the characteristics of a ZnO light-emitting diode (LED) comprised of a heterostructure of p-ZnO/n-GaN. The LED structure consisted of a phosphorus doped p-ZnO film with a hole concentration of 6.68×1017 cm−3 and a Si-doped n-GaN film with an electron concentration of 1.1×1018 cm−3. The I–V of the LED showed a threshold voltage of 5.4 V and an electroluminescence (EL) emission of 409 nm at room temperature. The EL emission peak at 409 nm was attributed to the band gap of p-ZnO which was reduced as the result of the band offset at the interface of p-ZnO and n-GaN.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence

Zero-field spin splitting in modulation-doped AlxGa1−xN/GaN two-dimensional electron systems

K. S. Cho, Tsai-Yu Huang, Hong-Syuan Wang, Ming-Gu Lin, Tse-Ming Chen, C.-T. Liang, Y. F. Chen, and Ikai Lo

Appl. Phys. Lett. 86, 222102 (2005); http://dx.doi.org/10.1063/1.1929876 (3 pages) | Cited 20 times

Online Publication Date: 24 May 2005

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Low-temperature magnetotransport measurements were performed on AlxGa1−xN/GaN two-dimensional electron systems. By studying the beating pattern in the Shubnikov–de Haas oscillations in a perpendicular magnetic field, we are able to measure the zero-field spin-splitting energies in our systems. Our experimental results demonstrate that the Rashba term due to structural inversion asymmetry is the dominant mechanism which gives rise to the measured zero-field spin splitting in our wurzite AlGaN/GaN structures. By utilizing the persistent photoconductivity (PPC) effect, we are able to increase the carrier density n in our AlGaN/GaN two-dimensional electron system. It is found that the Rashba spin-orbit splitting parameter α decreases with increasing n. We suggest that the formation of long-lived electron-hole pairs induced by the PPC effect decreases the large electric field near the AlGaN/GaN interface, causing α to decrease with increasing n.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Pz Photoconduction and photovoltaic effects
73.61.Ey III-V semiconductors
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Observation of large electron drift velocities in InN by ultrafast Raman spectroscopy

K. T. Tsen, C. Poweleit, D. K. Ferry, Hai Lu, and William J. Schaff

Appl. Phys. Lett. 86, 222103 (2005); http://dx.doi.org/10.1063/1.1931048 (3 pages) | Cited 37 times

Online Publication Date: 24 May 2005

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Electron transport in an InN film grown on GaN has been studied by transient Raman spectroscopy at T = 300 K. Our experimental results demonstrate that under the subpicosecond laser excitation and probing, electron drift velocity of carriers in the Γ valley can exceed its steady-state value by as much as 40%. Electron velocities have been found to cut off at around 2×108 cm/s, significantly larger than those observed for other III-V semiconductors, such as GaAs and InP. These experimental results have been compared with ensemble Monte Carlo simulations and good agreement has been obtained.
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73.61.Ey III-V semiconductors
78.30.Fs III-V and II-VI semiconductors

General model and segregation coefficient measurement for ultrashallow doping by excimer laser annealing

Jean-Numa Gillet, Jean-Yves Degorce, and Michel Meunier

Appl. Phys. Lett. 86, 222104 (2005); http://dx.doi.org/10.1063/1.1927275 (3 pages) | Cited 9 times

Online Publication Date: 24 May 2005

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A general model of ultrashallow doping by excimer laser annealing is derived from only one diffusion-segregation equation. In our model, the relative dopant profile after some laser shots reaches a stationary distribution, which only depends on the segregation and liquid-phase diffusion coefficients of the dopant but not on the laser-process parameters. From this result, a one-point method is proposed to experimentally determine the out-of-equilibrium segregation coefficient k. Only the relative dopant concentration at the material surface has to be measured prior to determine the k value. Experimental dopant profiles are compared to simulations generated with experimental k values.
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64.75.-g Phase equilibria
66.30.J- Diffusion of impurities
61.72.S- Impurities in crystals
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Electronic properties of a semiconducting oligomer/silicon (111) interface: Influence of silicon doping

V. Papaefthimiou and S. Kennou

Appl. Phys. Lett. 86, 222105 (2005); http://dx.doi.org/10.1063/1.1929073 (3 pages) | Cited 2 times

Online Publication Date: 24 May 2005

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The interface formation between a semiconducting oligomer and the p-doped Si(111) surface was investigated by X-ray and ultraviolet photoelectron spectroscopies (UPS) and the results were compared to the same oligomer/Si (n-doped) interface. The position of the energy levels of the bulk oligomer film was identical in both interfaces, while differences appeared at the first steps of the interface formation. The band bending at the interfaces was assessed from X-ray photoelectron spectra while the interfacial dipoles from the UPS results. A ∼ 0.30 eV dipole layer was observed at the oligomer/Si (p-doped) interface whereas the oligomer/Si (n-doped) interface is dipole free. The valence-band offset between silicon and the oligomer was found ∼ 0.40 eV in both cases.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
79.60.Jv Interfaces; heterostructures; nanostructures
73.20.At Surface states, band structure, electron density of states
61.72.uf Ge and Si

High-mobility nanocrystalline silicon thin-film transistors fabricated by plasma-enhanced chemical vapor deposition

Czang-Ho Lee, Andrei Sazonov, and Arokia Nathan

Appl. Phys. Lett. 86, 222106 (2005); http://dx.doi.org/10.1063/1.1942641 (3 pages) | Cited 54 times

Online Publication Date: 24 May 2005

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Hydrogenated nanocrystalline silicon (nc-Si:H) films were deposited by using 13.56 MHz plasma-enhanced chemical vapor deposition at 260 °C by means of a silane (SiH4) plasma heavily diluted with hydrogen (H2). The high-quality nc-Si:H film showed an oxygen concentration (CO) of ∼ 1.5×1017 at./cm3 and a dark conductivity (σd) of ∼ 10−6 S/cm, while the Raman crystalline volume fraction (Xc) was over 80%. Top-gate nc-Si:H thin-film transistors employing an optimized ∼ 100 nm nc-Si:H channel layer exhibited a field-effect mobility (μFE) of ∼ 150 cm2/V s, a threshold voltage (VT) of ∼ 2 V, a subthreshold slope (S) of ∼ 0.25 V/dec, and an ON∕OFF current ratio of ∼ 106.
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85.30.Tv Field effect devices
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Cd2+/NH3 treatment-induced formation of a CdSe surface layer on CuGaSe2 thin-film solar cell absorbers

M. Bär, S. Lehmann, M. Rusu, A. Grimm, I. Kötschau, I. Lauermann, P. Pistor, S. Sokoll, Th. Schedel-Niedrig, M. Ch. Lux-Steiner, Ch.-H. Fischer, L. Weinhardt, C. Heske, and Ch. Jung

Appl. Phys. Lett. 86, 222107 (2005); http://dx.doi.org/10.1063/1.1942638 (3 pages) | Cited 5 times

Online Publication Date: 25 May 2005

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CuGaSe2 (CGSe)-based high-gap thin-film solar cells have to date not reached their potential level of electrical performance. In order to elucidate possible shortcomings of the electronic interface structure, we have studied the initial stage of the CdS/CGSe interface formation by use of a simple Cd2+/NH3 treatment. As in the case of low-gap chalcopyrites, we find a Cd-containing surface layer, in the present case comprised of approximately one monolayer of CdSe. The results indicate that the CdS/CGSe interface is not abrupt, but contains intermediate layers. Furthermore, they shed light on possible surface modification schemes to enhance the overall performance of high-gap CGSe chalcopyrite solar cells.
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81.05.Dz II-VI semiconductors
84.60.Jt Photoelectric conversion
81.65.-b Surface treatments
68.35.Ct Interface structure and roughness

Deep impurity transitions involving cation vacancies and complexes in AlGaN alloys

K. B. Nam, M. L. Nakarmi, J. Y. Lin, and H. X. Jiang

Appl. Phys. Lett. 86, 222108 (2005); http://dx.doi.org/10.1063/1.1943489 (3 pages) | Cited 37 times

Online Publication Date: 26 May 2005

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Deep ultraviolet (UV) photoluminescence (PL) spectroscopy has been employed to study deep impurity transitions in AlxGa1−xN (0 ⩽ x ⩽ 1) epilayers. Two groups of deep impurity transitions were observed, which are assigned to the recombination between shallow donors and two different deep level acceptors involving cation vacancies (Vcation) and Vcation complexes in AlxGa1−xN alloys. These acceptor levels are pinned to two different energy levels common to AlxGa1−xN alloys (0 ⩽ x ⩽ 1). The deep impurity transitions related with Vcation complexes were observed in AlxGa1−xN alloys between x = 0 and 1, while those related with Vcation were only observed in AlxGa1−xN alloys between x = 0.58 and 1. This points out to the fact that the formation of Vcation is more favorable in Al-rich AlGaN alloys, while Vcation complexes can be formed in the whole range of x between 0 and 1. The implications of our findings to the UV optoelectronic devices using AlGaN alloys are also discussed.
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71.55.Eq III-V semiconductors
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.J- Point defects and defect clusters

Effect of inclined quantum wells on macroscopic capacitance-voltage response of Schottky contacts: Cubic inclusions in hexagonal SiC

K.-B. Park, Y. Ding, J. P. Pelz, M. K. Mikhov, Y. Wang, and B. J. Skromme

Appl. Phys. Lett. 86, 222109 (2005); http://dx.doi.org/10.1063/1.1935757 (3 pages) | Cited 8 times

Online Publication Date: 26 May 2005

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Finite-element calculations of Schottky diode capacitance-voltage (C-V) curves show that an array of subsurface inclined quantum wells (QWs) produce negligible change in shape and slope of C-V curves, but significantly reduce the intercept voltage. This is particularly important for hexagonal SiC, in which current- or process-induced cubic inclusions are known to behave as electron QWs. These calculations naturally explain the surprisingly large effect of cubic inclusions on the apparent 4H–SiC Schottky barrier determined by C-V measurements, and together with the measured C-V data indicate the QW subband energy in the inclusions to be ∼ 0.51 eV below the host 4H–SiC conduction band.
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85.30.Kk Junction diodes
85.30.Hi Surface barrier, boundary, and point contact devices
73.30.+y Surface double layers, Schottky barriers, and work functions
73.20.At Surface states, band structure, electron density of states
73.63.Hs Quantum wells
73.21.Fg Quantum wells
71.20.Nr Semiconductor compounds
02.70.Dh Finite-element and Galerkin methods
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Magnetic resonance signatures of grown-in defects in GaInNP alloys grown on a GaAs substrate

I. P. Vorona, T. Mchedlidze, M. Izadifard, I. A. Buyanova, W. M. Chen, Y. G. Hong, H. P. Xin, and C. W. Tu

Appl. Phys. Lett. 86, 222110 (2005); http://dx.doi.org/10.1063/1.1943487 (3 pages) | Cited 4 times

Online Publication Date: 27 May 2005

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Dilute-nitride Ga0.44In0.56NyP1−y alloys with y = 0–0.02, grown on a GaAs substrate using gas-source molecular beam epitaxy, are studied by the optically detected magnetic resonance (ODMR) technique. Grown-in paramagnetic defects were found to act as centers of nonradiative recombination. Resolved hyperfine structure for one of the detected ODMR signals suggests involvement of a Ga-interstitial or an As-antisite in the structure of the related defect.
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81.05.Ea III-V semiconductors
76.30.Mi Color centers and other defects
61.72.J- Point defects and defect clusters

n-type doping of (001)-oriented single-crystalline diamond by phosphorus

Hiromitsu Kato, Satoshi Yamasaki, and Hideyo Okushi

Appl. Phys. Lett. 86, 222111 (2005); http://dx.doi.org/10.1063/1.1944228 (3 pages) | Cited 56 times

Online Publication Date: 27 May 2005

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n-type doping of (001)-oriented single-crystalline diamond has been achieved using PH3 as doping gas and applying a newly optimized homoepitaxial growth technique based on plasma-enhanced chemical vapor deposition. Hall-effect measurements indicate n-type conductivity with highest mobilities of ∼ 350 cm2/Vs. Phosphorus doping is confirmed by secondary-ion mass spectroscopy.
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61.72.up Other materials
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.61.Cw Elemental semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
68.55.A- Nucleation and growth
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
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