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29 Mar 1999

Volume 74, Issue 13, pp. 1785-1922

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Optical properties of SrS:Cu,Ag two-component phosphors for electroluminescent devices

W. Park, T. C. Jones, and C. J. Summers

Appl. Phys. Lett. 74, 1785 (1999); http://dx.doi.org/10.1063/1.123085 (3 pages) | Cited 19 times

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The luminescence characteristics of a two-component electroluminescent (EL) phosphor, SrS:Cu,Ag, were investigated by optical spectroscopy. Motivated by the discovery of efficient EL from SrS:Cu, SrS:Ag was investigated but exhibited poor EL emission, even though it showed a superior blue color. Thus, SrS:Cu,Ag samples were prepared in order to investigate if the Ag luminescence could be sensitized to produce a more efficient and saturated blue EL phosphor. A detailed spectroscopic study on SrS:Cu,Ag revealed that the emission characteristics of SrS:Cu,Ag were identical to SrS:Ag, whereas the excitation spectra resembled SrS:Cu. These results demonstrated the efficient energy transfer from Cu to Ag, confirming the successful sensitization. © 1999 American Institute of Physics.
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78.60.Fi Electroluminescence

Continuous wave laser radiation at 669 nm from a self-frequency-doubled laser of YAl3(BO3)4:Nd3+

D. Jaque, J. Capmany, and J. García Solé

Appl. Phys. Lett. 74, 1788 (1999); http://dx.doi.org/10.1063/1.123086 (3 pages) | Cited 24 times

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We report on continuous-wave red laser radiation at 669 nm from a self-frequency-doubled laser of YAl3(BO3)4:Nd3+ operating at a fundamental wavelength of 1338 nm in the 4F3/2→4I13/2 laser channel of Nd3+ ion. Main laser characteristics at the fundamental wavelength are investigated as well as second harmonic generation properties. In nonoptimal preliminary experiments, 1 mW of red radiation is obtained for 900 mW pump power from a Ti:sapphire laser. © 1999 American Institute of Physics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Ultrafast nonlinear subwavelength solid immersion spectroscopy at T = 8 K

Martin Vollmer, Harald Giessen, Wolfgang Stolz, Wolfgang W. Rühle, Luke Ghislain, and Virgil Elings

Appl. Phys. Lett. 74, 1791 (1999); http://dx.doi.org/10.1063/1.123087 (3 pages) | Cited 24 times

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Pump–probe measurements with a subwavelength spatial resolution of 355 nm and a temporal resolution of 130 fs have been performed in a multiple quantum well sample at T = 8 K. A solid immersion lens was used to increase the spatial resolution to 0.41⋅λ and the effective numerical aperture to 1.23, demonstrating that the limit of conventional microscopy has been surpassed. The lateral carrier transport was investigated on subpicosecond timescales. © 1999 American Institute of Physics.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
78.47.-p Spectroscopy of solid state dynamics
42.79.Bh Lenses, prisms and mirrors
42.65.-k Nonlinear optics
78.66.Fd III-V semiconductors

Birefringent thin-film polarizers for use at normal incidence and with planar technologies

Ian Hodgkinson and Qi Hong Wu

Appl. Phys. Lett. 74, 1794 (1999); http://dx.doi.org/10.1063/1.123088 (3 pages) | Cited 19 times

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We discuss the design and fabrication of an all-dielectric thin-film polarizer that is compatible with existing planar technologies. This polarizer consists of a stack of quarter-wave biaxial layers. Each quarter-wave layer is formed by reactive electron-beam evaporation, using a bideposition technique that causes a columnar structure to grow perpendicular to the substrate, produces large normal-incidence linear birefringence, and avoids thickness wedging that is inherent in tilted-columnar biaxial layers. p-polarized light that is incident on the polarizer encounters an index-matched stack and is transmitted, whereas s-polarized light is rejected by a coexisting high-reflectance stack. A fabrication figure-of-merit of ten film periods per decade in the extinction ratio has been achieved in practice for a titanium oxide/tantalum oxide polarizer. © 1999 American Institute of Physics.
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42.79.Ci Filters, zone plates, and polarizers
78.20.Fm Birefringence
42.79.Wc Optical coatings
42.86.+b Optical workshop techniques
78.66.Nk Insulators
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Infrared imaging camera based on a Rydberg atom photodetector

Marcel Drabbels and L. D. Noordam

Appl. Phys. Lett. 74, 1797 (1999); http://dx.doi.org/10.1063/1.123089 (3 pages) | Cited 6 times

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A type of infrared imaging camera is demonstrated that uses gas-phase Rydberg atoms as photocathodes. The camera operates throughout the infrared part of the electromagnetic spectrum: λ = 1–100 μm. The first results are presented and the potential of the camera as an ultrafast detector and a wavelength selective detector is discussed. © 1999 American Institute of Physics.
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42.79.Pw Imaging detectors and sensors
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
32.80.Fb Photoionization of atoms and ions
06.60.Jn High-speed techniques (microsecond to femtosecond)
85.60.Ha Photomultipliers; phototubes and photocathodes

Surface electromagnetic wave excitation on one-dimensional photonic band-gap arrays

W. M. Robertson and M. S. May

Appl. Phys. Lett. 74, 1800 (1999); http://dx.doi.org/10.1063/1.123090 (3 pages) | Cited 15 times

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Experiments are described on the prism-coupled excitation of surface electromagnetic waves in one-dimensional photonic band-gap arrays. The low loss of photonic band-gap materials leads to narrow angular reflectivity resonances and high surface fields. These attributes, coupled with the ability to engineer the optical properties of photonic band-gap arrays, suggest these materials as powerful replacements for metal films in many applications that make use of surface-plasmon resonance. © 1999 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.79.Bh Lenses, prisms and mirrors
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Elastic constants and their pressure dependence of Zr41Ti14Cu12.5Ni9Be22.5C1 bulk metallic glass

Wei-Hua Wang, R. J. Wang, F. Y. Li, D. Q. Zhao, and M. X. Pan

Appl. Phys. Lett. 74, 1803 (1999); http://dx.doi.org/10.1063/1.123091 (3 pages) | Cited 62 times

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The acoustic velocities and their pressure dependence of bulk Zr41Ti14Cu12.5Ni9Be22.5C1 metallic glass (MG) have been measured up to 0.5 GPa by using a pulse echo overlap method. The elastic constants and thermodynamic parameters as well as their pressure dependence of the MG have been determined. The obtained elastic constants were compared to that of other kinds of glasses. More information about the microstructure, elastic properties, and glass forming ability of the MG was obtained. © 1999 American Institute of Physics.
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62.20.D- Elasticity
62.65.+k Acoustical properties of solids
62.50.-p High-pressure effects in solids and liquids
61.43.Fs Glasses
65.20.-w Thermal properties of liquids
65.40.gd Entropy
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

Observation of coherent phonons in silver nanoparticles embedded in BaO thin films

W. Qian, H. Yan, J. J. Wang, Y. H. Zou, L. Lin, and J. L. Wu

Appl. Phys. Lett. 74, 1806 (1999); http://dx.doi.org/10.1063/1.123092 (3 pages) | Cited 8 times

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Three kinds of coherent phonons (0.30, 1.90, and 3.75 THz) have been observed in silver nanoparticles embedded in BaO thin films by means of the femtosecond time-resolved pump-probe technique. The generation of 0.3 THz coherent phonons is attributed to the resonant excitation of localized surface plasmon of silver nanopaticles, and the resonant impulsive stimulated Raman scattering in silver aggregates is responsible for the generation of 1.90 and 3.75 THz coherent phonons. © 1999 American Institute of Physics.
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63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
61.46.-w Structure of nanoscale materials
78.47.-p Spectroscopy of solid state dynamics
78.30.-j Infrared and Raman spectra
78.66.Vs Fine-particle systems

Vertical self-alignment of quantum dots in superlattice

Y. W. Zhang, S. J. Xu, and C.-h. Chiu

Appl. Phys. Lett. 74, 1809 (1999); http://dx.doi.org/10.1063/1.123093 (3 pages) | Cited 20 times

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Self-alignment of quantum dots separated by spacer layers is investigated by using a three-dimensional finite element method. We find that the morphology of the top islands is not just simply a reproduction of the buried islands. It is dependent on the arrangement of the buried islands, the interruption time, and the spacer layer thickness. If the buried islands are uniform and regular, with appropriate choice of their spacing and aspect ratio and with a thin spacer layer, there exists a regime in which the steady-state top islands are always uniform and regular, vertically aligned, and stable against small perturbations. For a thicker spacer layer, due to the change of the strain energy density distribution on top of the spacer layer, the top islands are misaligned with the buried islands. If the buried islands are not uniform and regular, our simulations demonstrate the top islands may self-assemble into more uniform and regular arrangements. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Ultraviolet and blue emission from crystalline SiO2 coated with LiNbO3 and LiTaO3

G. G. Siu, X. L. Wu, Y. Gu, and X. M. Bao

Appl. Phys. Lett. 74, 1812 (1999); http://dx.doi.org/10.1063/1.123094 (3 pages) | Cited 20 times

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Crystalline SiO2 (α quartz) coated with LiNbO3 (LN) or LiTaO3 (LT) films emits two strengthened luminescence bands at 368 and 468 nm compared with those of pure α-SiO2, when excited with 280 nm light of a Xe lamp. These two bands strongly depend on the coating: the LN-coated α-SiO2 has a much stronger photoluminescence (PL) than the LT-coated α-SiO2. On the other hand, the two bands are different from those of α-SiO2 in that their excitation spectra do not have any noticeable band in the range 200–320 nm. They could be understood based on excitons in the α-SiO2 surface, which are induced by the photorefractive effect of the coated films. The 368 nm PL band is attributed to the optical transitions of the E′ defect pairs and the 468 nm PL band to the radiative recombination of the self-trapped excitons. © 1999 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
71.35.Gg Exciton-mediated interactions
78.20.-e Optical properties of bulk materials and thin films

Charge trap dynamics in a SiO2 layer on Si by scanning capacitance microscopy

C. J. Kang, G. H. Buh, S. Lee, C. K. Kim, K. M. Mang, C. Im, and Y. Kuk

Appl. Phys. Lett. 74, 1815 (1999); http://dx.doi.org/10.1063/1.123095 (3 pages) | Cited 30 times

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Trapped electrons and holes, and their dynamics, were visualized from spatially resolved capacitance–voltage (C–V) curves and dC/dV images using scanning capacitance microscopy. A trapped charge of 10−16–10−18 C, localized within 2 μm diam circular test structures, was imaged. The detrapping process of the trapped electrons can be explained with a quantum-mechanical tunneling model. © 1999 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.20.At Surface states, band structure, electron density of states

The intrinsic temperature effect of the Raman spectra of graphite

PingHeng Tan, YuanMing Deng, Qian Zhao, and WenChao Cheng

Appl. Phys. Lett. 74, 1818 (1999); http://dx.doi.org/10.1063/1.123096 (3 pages) | Cited 50 times

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The Raman spectra of ion-implanted highly oriented pyrolytic graphite (HOPG) are reported, in which an additional mode at 1083 cm−1 and three doublet structures in the positions of ∼ 1350, ∼ 2450, and ∼ 2710 cm−1 are revealed. Noticeable frequency shifts are observed for all the Raman bands between the spectra excited with different laser powers, which are interpreted as the pure temperature effect and a downshift in the C–C stretching frequency induced by the thermal expansion. Moreover, the pure temperature effect (dω/dT)V without anharmonic contribution is achieved in pristine HOPG. The results suggest that the pure temperature effect without anharmonic contribution plays an important role in the frequency shifts with temperature. © 1999 American Institute of Physics.
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65.40.De Thermal expansion; thermomechanical effects
63.20.Ry Anharmonic lattice modes
78.30.Hv Other nonmetallic inorganics

Anisotropic photoluminescence in incomplete three-dimensional photonic band-gap environments

S. G. Romanov, A. V. Fokin, and R. M. De La Rue

Appl. Phys. Lett. 74, 1821 (1999); http://dx.doi.org/10.1063/1.123097 (3 pages) | Cited 45 times

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The effect of an incomplete three-dimensional photonic band-gap structure upon the wideband photoluminescence from bare opal and opal impregnated with ZnS has been studied by means of angular-resolved photoluminescence. It has been shown that the photoluminescence becomes anisotropic in accordance with the angular dispersion of the stop band. Suppression of the spontaneous emission in the stop-band energy region and amplification of the spontaneous emission at the edge of the stop band have both been demonstrated. © 1999 American Institute of Physics.
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78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
42.70.Qs Photonic bandgap materials
42.50.-p Quantum optics
78.45.+h Stimulated emission

Microstructural study of optically degraded ZnCdSe quantum wells

S. Tomiya, H. Noguchi, Y. Sanaka, T. Hino, S. Taniguchi, and A. Ishibashi

Appl. Phys. Lett. 74, 1824 (1999); http://dx.doi.org/10.1063/1.123098 (3 pages) | Cited 3 times

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The defect structure of optically degraded ZnCdSe quantum wells was investigated using transmission electron microscopy. The defects were composed of the dislocation dipoles with a Burgers vector of b = −(a/2)[101] inclined at 45° to the (001) plane. The dislocation dipoles consist of two segments aligned along the [1math0] direction and the [120] direction. The [1math0] dipole segments lying in the (11math) plane were developed by the recombination-enhanced dislocation glide process, while the [mathmath0] dipole segments lying in the (math11) plane were developed by the recombination-enhanced dislocation climb process. Both processes operate simultaneously. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.05.Dz II-VI semiconductors

Effects of high magnetic field on the morphology of carbon nanotubes and selective synthesis of fullerenes

Haruo Yokomichi, Hiroyuki Sakima, Masaki Ichihara, Fumiko Sakai, Kikuo Itoh, and Naoki Kishimoto

Appl. Phys. Lett. 74, 1827 (1999); http://dx.doi.org/10.1063/1.123099 (3 pages) | Cited 6 times

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Carbon nanotubes and fullerenes were synthesized by arc discharge in a He gas atmosphere under a high magnetic field up to 10 T. Morphology and the yield of these nanotubes were investigated by scanning electron microscopy and transmission electron microscopy (TEM). The yield and type of fullerenes were also evaluated by ultraviolet visual spectroscopy. TEM images revealed that thin collapsed nanotubes having larger curvature were synthesized under a high magnetic field, in particular at 10 T. Furthermore, the ratio of C70 to C60 concentration was found to vary depending on the magnitude of the magnetic field during arc discharge. Based on these results, the effects of magnetic field on the synthesis of carbon nanotubes and fullerenes are discussed. © 1999 American Institute of Physics.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
81.05.ub Fullerenes and related materials
78.40.Ri Fullerenes and related materials
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Nucleation of chemical vapor deposited silicon nitride on silicon dioxide

M. Copel, P. R. Varekamp, D. W. Kisker, F. R. McFeely, K. E. Litz, and M. M. Banaszak Holl

Appl. Phys. Lett. 74, 1830 (1999); http://dx.doi.org/10.1063/1.123100 (3 pages) | Cited 3 times

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We have studied the early stages of silicon nitride chemical vapor deposition (CVD) on silicon dioxide using medium energy ion scattering. The growth mode consists of island nucleation followed by coalescence. Similar behavior is observed for films grown using different precursors and reactor environments, indicating that the growth mode is caused by the fundamental nonwetting nature of the nitride/oxide interface under the conditions used for CVD. © 1999 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Effects of nitrogen implantation in silicon for shallow p+-n junction formation

Chang-Yong Kang, Won-Joo Cho, Dae-Gwan Kang, Young-Jong Lee, and Jeong-Mo Hwang

Appl. Phys. Lett. 74, 1833 (1999); http://dx.doi.org/10.1063/1.123684 (3 pages) | Cited 3 times

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This letter will present the effects of nitrogen implantation on shallow p+-n junction formation in silicon. The p+-n junctions fabricated at different implantation conditions and heat budgets were characterized by secondary ion mass spectroscopy, current–voltage and capacitance–voltage measurements, and analyzed by transport of ions in matter simulation. The capacitance–voltage measurements of nitrogen implanted samples revealed the one-sided abrupt junction properties, and the current–voltage measurements indicated the shallow junction characteristics due to boron diffusion suppression by nitrogen. The activation energy is about 0.39 eV for temperatures below 80 °C, and its dominant leakage mechanism is phonon-assisted tunneling. At a reverse bias of −3 V, the leakage current density was 5.217×10−8 A/cm2 at −3 V, which is comparable to that of a conventional p+-n junction. © 1999 American Institute of Physics.
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61.72.uf Ge and Si
61.80.Jh Ion radiation effects
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.82.Fk Semiconductors

Extrinsic surface states traced by surface photovoltage in photoemission

L. Kipp, R. Adelung, N. Trares-Wrobel, and M. Skibowski

Appl. Phys. Lett. 74, 1836 (1999); http://dx.doi.org/10.1063/1.123685 (3 pages) | Cited 5 times

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Surface defect states are generally not directly accessable experimentally. In standard photoemission this is because of their low densities which are several orders of magnitude lower than intrinsic states. On semiconductor surfaces, however, they may induce band bending which is changing characteristically upon bias light intensity and temperature variation. We show that fitting surface photovoltage measured by photoemission to calculations considering high bias light levels and finite electric fields in the space charge layer explicitly allow for a quantitative determination of surface defect densities and the associated energy levels. The results obtained for the defect densities were corroborated by scanning tunneling microscopy investigations. For the covalent and layered semiconductor surfaces GaAs(110) and WSe2:Rb serving as model systems, we show the wide applicability and reliability of this technique. © 1999 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
72.40.+w Photoconduction and photovoltaic effects
73.25.+i Surface conductivity and carrier phenomena
71.55.Ht Other nonmetals
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Storage of electrons and holes in self-assembled InAs quantum dots

M. C. Bödefeld, R. J. Warburton, K. Karrai, J. P. Kotthaus, G. Medeiros-Ribeiro, and P. M. Petroff

Appl. Phys. Lett. 74, 1839 (1999); http://dx.doi.org/10.1063/1.123686 (3 pages) | Cited 26 times

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We report spectroscopic measurements of charge-tunable quantum dots. The samples contain vertically aligned double dots which we can fill with electrons from a back contact. We show how we can also accumulate holes in the dots by illuminating the samples with below band gap radiation when a large negative bias is applied. We argue that this is possible through a large disparity in the electron and hole tunneling times. Interband spectroscopy reveals a strong reduction in the quantization energy for the dots in the second layer. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.55.Cr III-V semiconductors
73.40.Gk Tunneling

Resonant hole localization and anomalous optical bowing in InGaN alloys

L. Bellaiche, T. Mattila, L.-W. Wang, S.-H. Wei, and A. Zunger

Appl. Phys. Lett. 74, 1842 (1999); http://dx.doi.org/10.1063/1.123687 (3 pages) | Cited 103 times

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Using large supercell empirical pseudopotential calculations, we show that alloying of GaN with In induces localization in the hole wave function, resonating within the valence band. This occurs even with perfectly homogeneous In distribution (i.e., no clustering). This unusual effect can explain simultaneously exciton localization and a large, composition-dependent band gap bowing coefficient in InGaN alloys. This is in contrast to conventional alloys such as InGaAs that show a small and nearly composition-independent bowing coefficient. We further predict that (i) the hole wave function localization dramatically affects the photoluminescence intensity in InGaN alloys and (ii) the optical properties of InGaN alloys depend strongly on the microscopic arrangement of In atoms. © 1999 American Institute of Physics.
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71.20.Nr Semiconductor compounds
78.55.Cr III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
71.35.-y Excitons and related phenomena

Nonalloyed high temperature ohmic contacts on Te-doped InP

F. Ren, M. J. Antonell, C. R. Abernathy, S. J. Pearton, J. R. LaRoche, M. W. Cole, J. R. Lothian, and R. W. Gedridge

Appl. Phys. Lett. 74, 1845 (1999); http://dx.doi.org/10.1063/1.123688 (3 pages) | Cited 3 times

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We report on a thermal stability study of WSi0.79 contacts on Te-doped InP. The epitaxial InP layers were grown on Fe-doped semi-insulating InP substrates by metalorganic molecular beam epitaxy. Tri-isopropylindium-di-isopropyltellurium was used as the Te precursor and the doping level was 1.4×1020 cm−3. Contact metal, amorphous WSi0.79, was sputtered from a composite and an excellent specific contact resistance of 1×10−6 Ω cm2 was achieved. The specific contact resistivity was also measured at different temperature (25–200 °C) and it stayed fair contact. This is clear indication that the current transport through the contact dominates by tunneling. After alloying at temperatures up to 600 °C, there is no obvious change of specific contact resistance or sheet resistance. After 700 °C annealing, there was significant P out-diffusion detected and the specific contact resistance began to degrade. However, the contact metal morphology and edge definition were unaffected. After 800 °C annealing, there was evidence of In out-diffusion after and the surface morphology became rough. © 1999 American Institute of Physics.  
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
81.40.Gh Other heat and thermomechanical treatments
81.40.Rs Electrical and magnetic properties related to treatment conditions
68.35.Fx Diffusion; interface formation
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Ct Interface structure and roughness

Technique for producing highly planar Si/SiO0.64Ge0.36/Si metal–oxide–semiconductor field effect transistor channels

T. J. Grasby, C. P. Parry, P. J. Phillips, B. M. McGregor, R. J. H. Morris,, G. Braithwaite, T. E. Whall, E. H. C. Parker, R. Hammond, A. P. Knights, and P. G. Coleman

Appl. Phys. Lett. 74, 1848 (1999); http://dx.doi.org/10.1063/1.123689 (3 pages) | Cited 11 times

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Si/Si0.64Ge0.36/Si heterostructures have been grown at low temperature (450 °C) to avoid the strain-induced roughening observed for growth temperatures of 550 °C and above. The electrical properties of these structures are poor, and thought to be associated with grown-in point defects as indicated in positron annihilation spectroscopy. However, after an in situ annealing procedure (800 °C for 30 min) the electrical properties dramatically improve, giving an optimum 4 K mobility of 2500 cm2 V−1 s−1 for a sheet density of 6.2×1011 cm−2. The low temperature growth yields highly planar interfaces, which are maintained after anneal as evidenced from transmission electron microscopy. This and secondary ion mass spectroscopy measurements demonstrate that the metastably strained alloy layer can endure the in situ anneal procedure necessary for enhanced electrical properties. Further studies have shown that the layers can also withstand a 120 min thermal oxidation at 800 °C, commensurate with metal–oxide–semiconductor device fabrication. © 1999 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.Tv Field effect devices
68.35.Ct Interface structure and roughness
61.72.Cc Kinetics of defect formation and annealing
73.50.Dn Low-field transport and mobility; piezoresistance
78.70.Bj Positron annihilation
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.65.Mq Oxidation
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Room-temperature photoluminescence, contactless electroreflectance, and x-ray characterization of a double-side delta-doped GaAlAs/InGaAs high electron mobility transistor structure

Y. S. Huang, W. D. Sun, L. Malikova, Fred H. Pollak, I. Ferguson, H. Hou, Z. C. Feng, T. Ryan, and E. B. Fantner

Appl. Phys. Lett. 74, 1851 (1999); http://dx.doi.org/10.1063/1.123690 (3 pages) | Cited 5 times

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Using room-temperature photoluminescence and contactless electroreflectance we have characterized a double-side delta-doped Ga0.8Al0.2As/In0.2Ga0.8As pseudomorphic high electron mobility transistor structure fabricated by metal-organic chemical vapor deposition. Signals have been observed from every region of the sample making it possible to evaluate In and Al compositions, channel width, and two-dimensional electron gas density as well as the properties of the GaAs/GaAlAs superlattice buffer layer. The optical determination of the In composition and channel width are in good agreement with an x-ray measurement. © 1999 American Institute of Physics.
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85.30.Tv Field effect devices
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.20.Jq Electro-optical effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

GaN evaporation in molecular-beam epitaxy environment

N. Grandjean, J. Massies, F. Semond, S. Yu. Karpov, and R. A. Talalaev

Appl. Phys. Lett. 74, 1854 (1999); http://dx.doi.org/10.1063/1.123691 (3 pages) | Cited 37 times

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GaN(0001) thick layers were grown on c-plane sapphire substrates by molecular-beam epitaxy using NH3. The evaporation of such GaN layers in vacuum was studied as a function of substrate temperature. In situ laser reflectivity was used to quantitatively measure the decomposition rate of the GaN(0001) plane. It is nearly zero below 750 °C, increases rapidly above 800 °C, and reaches 1 μm/h at 850 °C. An activation energy of 3.6 eV is deduced for the thermal decomposition of GaN in vacuum. The evaporation rate as a function of the incident NH3 flux was also investigated for different substrate temperatures. A kinetic model is applied for the interpretation of the experimental results. © 1999 American Institute of Physics.
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68.60.Dv Thermal stability; thermal effects
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
64.70.Hz Solid-vapor transitions
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
78.66.Fd III-V semiconductors

Influence of curvature on impurity gettering by nanocavities in Si

François Schiettekatte, Carl Wintgens, and Sjoerd Roorda

Appl. Phys. Lett. 74, 1857 (1999); http://dx.doi.org/10.1063/1.123692 (3 pages) | Cited 11 times

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Competition for Au gettering in Si between two cavity layers of different diameter (34 and 12 nm) is examined. Au is initially contained in the large cavity layer made by He implantation. Transport of Au towards the second, small diameter cavity layer is measured by ion scattering. The true surface in both layers is determined by electron microscopy. Small cavities are found to be four times more efficient gettering sites than large cavities for the same amount of internal surface. This difference is explained by a simple model based on curvature thermodynamics, faceting, and surface reconstruction. © 1999 American Institute of Physics.
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71.55.Cn Elemental semiconductors
61.72.Yx Interaction between different crystal defects; gettering effect
81.65.Tx Gettering
68.35.Dv Composition, segregation; defects and impurities
81.05.Cy Elemental semiconductors
73.20.Hb Impurity and defect levels; energy states of adsorbed species
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