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20 Jul 1998

Volume 73, Issue 3, pp. 279-419

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Annealing cycle dependence of preferential arsenic precipitation in AlGaAs/GaAs layers

C.-Y. Hung, J. S. Harris, A. F. Marshall, and R. A. Kiehl

Appl. Phys. Lett. 73, 330 (1998); http://dx.doi.org/10.1063/1.121824 (3 pages) | Cited 3 times

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The spatial distribution of arsenic precipitates formed in a nonstoichiometric AlGaAs/GaAs quantum well is examined for different annealing temperatures and times. Preferential precipitation in the GaAs layer of samples annealed at 600 °C is found to be much weaker than in samples annealed at 850 °C because of the reduced diffusion of arsenic at lower temperatures. Nevertheless, it is demonstrated that strong preferential precipitation is possible at low annealing temperatures, provided that the annealing time is sufficiently long. Limitations to the preferential precipitation process imposed by interface mixing and the decrease in gallium vacancy concentration during annealing are also examined. © 1998 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Selective-area and lateral epitaxial overgrowth of III–N materials by metal organic chemical vapor deposition

J. Park, P. A. Grudowski, C. J. Eiting, and R. D. Dupuis

Appl. Phys. Lett. 73, 333 (1998); http://dx.doi.org/10.1063/1.121825 (3 pages) | Cited 30 times

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We describe the characteristics of single-crystal GaN regions obtained by selective-area and subsequent lateral epitaxial overgrowth using metal organic chemical vapor deposition. Under certain deposition conditions, the surface kinetics of the metal organic chemical vapor deposition process results in lateral growth of single-crystal GaN over the masked region. The lateral-to-vertical relative growth rate depends upon the orientation of stripe openings, the ratio of the “open” stripe width to the “masked” stripe width, and the growth conditions (e.g., temperature and V/III ratio). The specific orientations of the growth facets on the sidewalls of the laterally growing stripes are also dependent upon the growth conditions. The cathodoluminescence intensity of the GaN films indicate that improved materials are grown over the oxide mask. © 1998 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Fd III-V semiconductors

Study of microstructure of high stability hydrogenated amorphous silicon films by Raman scattering and infrared absorption spectroscopy

Shuran Sheng, Xianbo Liao, Guanglin Kong, and Hexiang Han

Appl. Phys. Lett. 73, 336 (1998); http://dx.doi.org/10.1063/1.121826 (3 pages) | Cited 13 times

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The microstructure, hydrogen bonding configurations and hydrogen content of high quality and stable hydrogenated amorphous silicon (a-Si:H) films prepared by a simple “uninterrupted growth/annealing” plasma enhanced chemical vapor deposition technique have been investigated by Raman scattering and infrared absorption spectroscopy. The high stability a-Si:H films contain small amounts of a microcrystalline phase and not less hydrogen (10–16 at. %), particularly, the clustered phase hydrogen. Besides, the hydrogen distribution is very inhomogeneous. Some of these results are substantially distinct from those of conventional device-quality a-Si:H film or stable a-Si:H films prepared by the other techniques examined to date. The stability of a-Si:H films appears to have no direct correlation with the hydrogen content or the clustered phase hydrogen concentration. The ideal a-Si:H network with high stability and low defect density is perhaps not homogeneous. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.66.Jg Amorphous semiconductors; glasses
78.35.+c Brillouin and Rayleigh scattering; other light scattering
81.05.Cy Elemental semiconductors
61.43.Dq Amorphous semiconductors, metals, and alloys
81.05.Gc Amorphous semiconductors
78.30.Am Elemental semiconductors and insulators

Effects of piezoelectric field on defect formation, charge transfer, and electron transport at GaN/AlxGa1−xN interfaces

L. Hsu and W. Walukiewicz

Appl. Phys. Lett. 73, 339 (1998); http://dx.doi.org/10.1063/1.121827 (3 pages) | Cited 30 times

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We have calculated the donor defect profiles in pseudomorphic AlxGa1−xN layers grown on GaN, taking into account the effects of the strain polarization field on the defect formation energy. Under certain conditions, the defect concentration may be enhanced by more than one order of magnitude. These large concentrations combined with the band bending effects of the piezoelectric field makes the charge transfer from the AlxGa1−xN barrier to the GaN well extremely efficient, resulting in a two-dimensional electron gas of very high density and low mobility. These results explain recent experimental observations of large electron densities found in nominally undoped GaN/AlGaN heterostructures. © 1998 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
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
73.61.Ey III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Bi4Ti3O12 ferroelectric thin film ultraviolet detectors

L. Pintilie, M. Alexe, A. Pignolet, and D. Hesse

Appl. Phys. Lett. 73, 342 (1998); http://dx.doi.org/10.1063/1.121828 (3 pages) | Cited 25 times

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Bi4Ti3O12 (BiT) ferroelectric thin films were used as photoconductive or photovoltaic ultraviolet detectors. The maximum of the spectral distribution lies around 370 or 390 nm, depending on whether the incident light is continuous or modulated. The maximum current responsivity obtained for the films annealed at 700 °C is about 0.01 A/W. The specific detectivity is 5.5×108 cm W−1 Hz1/2 at a modulation frequency of 20 Hz. The frequency characteristics of the photovoltaic signal measured in modulated light suggests a 1/f frequency dependence of this signal. © 1998 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
42.79.Pw Imaging detectors and sensors
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Optical monitoring of InP monolayer growth rates

P. J. Parbrook, K. B. Ozanyan, M. Hopkinson, C. R. Whitehouse, Z. Sobiesierski, and D. I. Westwood

Appl. Phys. Lett. 73, 345 (1998); http://dx.doi.org/10.1063/1.121829 (3 pages) | Cited 1 time

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Reflection anisotropy (RA) spectroscopy has been used to examine the in vacuo (001) surface of InP before and during growth by molecular beam epitaxy (MBE). The dominant effect on the RA signal occurring the initiation of growth is the change in the surface V/III ratio, caused by the exposure of the surface to the incident indium flux. During MBE growth of InP under commonly used conditions, RA oscillations are clearly observed. These oscillations have been confirmed to correspond to the growth of InP monolayers. The oscillations are tentatively ascribed to the variation in P coverage during the growth of each monolayer of material. © 1998 American Institute of Physics.
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81.05.Ea III-V semiconductors
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.20.-e Optical properties of bulk materials and thin films

Heteroepitaxy of ZnO on GaN and its implications for fabrication of hybrid optoelectronic devices

R. D. Vispute, V. Talyansky, S. Choopun, R. P. Sharma, T. Venkatesan, M. He, X. Tang, J. B. Halpern, M. G. Spencer, Y. X. Li, L. G. Salamanca-Riba, A. A. Iliadis, and K. A. Jones

Appl. Phys. Lett. 73, 348 (1998); http://dx.doi.org/10.1063/1.121830 (3 pages) | Cited 166 times

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ZnO thin films have been grown heteroepitaxially on epi-GaN/sapphire (0001) substrates. Rutherford backscattering spectroscopy, ion channeling, and high resolution transmission electron microscopy studies revealed high-quality epitaxial growth of ZnO on GaN with an atomically sharp interface. The x-ray diffraction and ion channeling measurements indicate near perfect alignment of the ZnO epilayers on GaN as compared to those grown directly on sapphire (0001). Low-temperature cathodoluminescence studies also indicate high optical quality of these films presumably due to the close lattice match and stacking order between ZnO and GaN. Lattice-matched epitaxy and good luminescence properties of ZnO/GaN heterostructures are thus promising for ultraviolet lasers. These heterostructures demonstrate the feasibility of integrating hybrid ZnO/GaN optoelectronic devices. © 1998 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Hf II-VI semiconductors
81.05.Dz II-VI semiconductors
68.55.-a Thin film structure and morphology

Electrical characterization of alternating-current thin-film electroluminescent devices

A. N. Krasnov, R. C. Bajcar, and P. G. Hofstra

Appl. Phys. Lett. 73, 351 (1998); http://dx.doi.org/10.1063/1.121831 (3 pages) | Cited 4 times

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We suggest a formalism built on the analogy between the pressure-volume (P–math) diagram of a gas system and the charge-voltage (Q–V) characteristics of the alternating-current thin-film electroluminescent (ACTFEL) device. The formalism extends the understanding of the processes in ACTFEL devices and the complete characterization of their internal parameters based on the Q–V diagram.© 1998 American Institute of Physics.
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85.60.Jb Light-emitting devices

Observation of spin splitting in single InAs self-assembled quantum dots in AlAs

A. S. G. Thornton, T. Ihn, P. C. Main, L. Eaves, and M. Henini

Appl. Phys. Lett. 73, 354 (1998); http://dx.doi.org/10.1063/1.121832 (3 pages) | Cited 44 times

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Using magneto-tunneling spectroscopy, we observe the Zeeman spin splitting of the ground state of a single InAs quantum dot grown within AlAs. We obtain values for the g factor of different quantum dots between +0.52±0.08 and +1.6±0.2, with magnetic field applied in the plane of the dot. This value for the g factor is considerably different from that of bulk InAs (g = −14.8), and we explain this using a simple three band k⋅p calculation. Using the spin split states of the dot as a probe, we observe the complete spin polarization of the emitter accumulation layer. © 1998 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Ey III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
78.20.Ls Magneto-optical effects

Hybrid ferromagnetic/semiconductor Hall effect device

J. Reijniers and F. M. Peeters

Appl. Phys. Lett. 73, 357 (1998); http://dx.doi.org/10.1063/1.121833 (3 pages) | Cited 28 times

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The diffusive classical transport of a two-dimensional electron gas (2DEG) in a Hall cross, subjected to a locally inhomogeneous magnetic field resulting from an in plane magnetized ferromagnetic film deposited above the 2DEG, is investigated. The magnetic field profile in the 2DEG is obtained analytically and the Hall resistance is calculated for various configurations. Our results are in good agreement with the recent experimental results of Johnson et al. [Appl. Phys. Lett. 71, 974 (1997)] on a novel magnetoelectronic device. The output of the device scales inversely with both the size of the voltage and the current probes. © 1998 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.40.Ns Metal-nonmetal contacts
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
75.70.Ak Magnetic properties of monolayers and thin films

Floating low-temperature radio-frequency plasma oxidation of polycrystalline silicon-germanium

Zhineng Fan, Gang Zhao, Paul K. Chu, Zhonghe Jin, Hoi S. Kwok, and Man Wong

Appl. Phys. Lett. 73, 360 (1998); http://dx.doi.org/10.1063/1.121834 (3 pages) | Cited 5 times

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Low temperature oxide formation is an important process in the fabrication of thin-film transistors (TFT) used in active-matrix liquid crystal displays. However, low temperature oxide is prone to have defects at the SiO2/polycrystalline–SiGe interfaces. We have recently developed a novel rf (radio frequency) plasma oxidation method for polycrystalline SiGe (poly-SiGe) materials. The poly-SiGe wafers are oxidized in an oxygen rf plasma with the samples electrically floating. That is, the sample voltage is the same as the sheath potential of the floating wall and is always negative with respect to the bulk of the plasma since electrons have higher mobility than ions. The slightly negative potential on the wafers attracts low energy oxygen ions from the plasma and the resulting damage on the wafers is thus lower than that induced by the more commonly used and energetic electron cyclotron resonance (ECR) source. No deliberate heating is applied during oxidation since the samples are heated spontaneously by the plasma, but the temperature is measured to be below 100 °C throughout the entire process. The oxidation rate is comparable to that of ECR plasma oxidation. Depth profiles are acquired by Auger electron spectroscopy and the interfaces are examined by x-ray photoelectron spectroscopy. The n-channel metal oxide silicon device fabricated on the as-grown gate oxide shows good electrical characteristics. The process is thus compatible with inexpensive large-area, low-temperature fabrication of TFTs on glass substrates. © 1998 American Institute of Physics.
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81.05.Hd Other semiconductors
81.65.Mq Oxidation
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
79.60.Jv Interfaces; heterostructures; nanostructures
79.20.Fv Electron impact: Auger emission
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Spontaneous splitting of ferromagnetic (Ga, Mn)As valence band observed by resonant tunneling spectroscopy

H. Ohno, N. Akiba, F. Matsukura, A. Shen, K. Ohtani, and Y. Ohno

Appl. Phys. Lett. 73, 363 (1998); http://dx.doi.org/10.1063/1.121835 (3 pages) | Cited 91 times

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Current–voltage characteristics of AlAs/GaAs/AlAs double barrier resonant tunneling diodes with ferromagnetic p-type (Ga, Mn)As on one side and p-type GaAs on the other have been studied. A series of resonant peaks have been observed in both polarities, i.e., injecting holes from p-type GaAs and from (Ga, Mn)As. When holes are injected from the (Ga, Mn)As side, spontaneous resonant peak splitting has been observed below the ferromagnetic transition temperature of (Ga, Mn)As without magnetic field. The temperature dependence of the splitting is explained by the the spontaneous spin splitting in the valence band of ferromagnetic (Ga, Mn)As. © 1998 American Institute of Physics.
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
85.30.Kk Junction diodes
73.20.At Surface states, band structure, electron density of states

Electron and hole tunneling in a moderate density quantum dot ensemble with shallow confinement potentials

D. L. Huffaker and D. G. Deppe

Appl. Phys. Lett. 73, 366 (1998); http://dx.doi.org/10.1063/1.121836 (3 pages) | Cited 24 times

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Data are presented on InAlGaAs quantum dot ensembles that possess different degrees of lateral tunnel coupling for electrons and holes. Atomic force microscope images show that even for moderate densities ( ∼ 4.8×1010 cm−2), but with shallow potentials, many dots of an ensemble can be in such close proximity that tunneling is expected for both electrons and holes. On average, however, holes remain confined while electrons freely tunnel. Even with electron tunneling, single dot emission is observed for small area light emitting diodes. © 1998 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
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.40.Gk Tunneling
85.60.Jb Light-emitting devices

Resistivity anisotropy in ordered InxGa1−xP grown at 640 °C

J. Novák, S. Hasenöhrl, R. Kúdela, M. Kučera, D. Wüllner, and H.-H. Wehmann

Appl. Phys. Lett. 73, 369 (1998); http://dx.doi.org/10.1063/1.121837 (3 pages) | Cited 5 times

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The anisotropy of electrical properties in ordered InxGa1−xP epitaxial layers was studied. These samples were prepared by a low-pressure metalorganic chemical vapor phase epitaxy technique at the growth temperature of 640 °C. Resistivity measurements using a four-point-probe method have shown that samples with a low misfit value (0–1.5×10−3) are electrically uniform. For samples with higher misfit the anisotropy of resistivity markedly increases up to a maximum of 950. Comparing the results obtained from x-ray diffraction, low temperature photoluminescence, and atomic force microscopy experiments, we have shown that lattice mismatch can support the evolution and extension of the ordering effect in the InxGa1−xP layers. © 1998 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Nondestructive evaluation of carrier concentration in the channel layer of In0.5Ga0.5P/In0.2Ga0.8As/GaAs heterostructure field-effect transistors by Raman scattering

Gako Araki, Takumi Nittono, Tomofumi Furuta, and Fumiaki Hyuga

Appl. Phys. Lett. 73, 372 (1998); http://dx.doi.org/10.1063/1.121838 (3 pages) | Cited 5 times

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Carrier concentration (N) in the channel layers of pseudomorphic In0.5Ga0.5P/In0.2Ga0.8As/GaAs heterostructure field-effect transistors (HFETs) is evaluated by Raman scattering measurements. The coupled mode between the InGaAs longitudinal optical phonons and electrons in the InGaAs channel shifts continuously to a low wave number with an increasing N in the InGaAs channel. Preliminary calculation indicates that N can be determined with an error of less than 0.35×1018/cm3 in the 1018/cm3 order range, which corresponds to a 100 mV HFET threshold voltage. Raman scattering measurement is nondestructive and has a high spatial resolution as small as 1 μm in diameter. Thus, this measurement is promising in HFET wafer selection. © 1998 American Institute of Physics.
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85.30.Tv Field effect devices
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
63.20.K- Phonon interactions
06.60.Mr Testing and inspecting procedures

Broadening of near-band-gap photoluminescence in n-GaN films

E. Iliopoulos, D. Doppalapudi, H. M. Ng, and T. D. Moustakas

Appl. Phys. Lett. 73, 375 (1998); http://dx.doi.org/10.1063/1.121839 (3 pages) | Cited 46 times

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This letter addresses the broadening mechanism of the near-band-gap photoluminescence in GaN films doped n type with silicon. The films were produced by plasma assisted molecular beam epitaxy and their carrier concentration was varied systematically from 1015 to 1020 cm−3. The photoluminescence was excited with a 10 mW He–Cd laser at 77 K. At low carrier concentration (<1017 cm−3) the photoluminescence peak has a full width at half maximum of about 18 meV, while at high carrier concentration (>1018 cm−3) the full width at half maximum increases monotonically with carrier concentration up to about 120 meV. The broadening of the line at high carrier concentration is attributed to tailing of the density of states caused by potential fluctuations due to randomly distributed impurities. The data were quantitatively analyzed, as a function of carrier concentration and compensation ratio, using the impurity band broadening model of Morgan [Phys. Rev. 139, A343 (1965)], and the agreement between model and experimental data supports the model’s validity and suggests a potential method of determining the compensation in degenerate nitride semiconductors. © 1998 American Institute of Physics.
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73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
71.20.Nr Semiconductor compounds
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