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21 Feb 2000

Volume 76, Issue 8, pp. 943-1075

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Arsenic impurities in GaN

Chris G. Van de Walle and J. Neugebauer

Appl. Phys. Lett. 76, 1009 (2000); http://dx.doi.org/10.1063/1.125922 (3 pages) | Cited 36 times

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We present a comprehensive first-principles investigation of arsenic incorporation in GaN. Incorporation of As on the N site, which has previously been implicitly assumed, is favorable only under n-type conditions in a Ga-rich environment. Less Ga-rich conditions, and particularly p-type doping, strongly favor incorporation of As on the Ga site, where it behaves as a deep double donor. Arsenic thus acts as a compensating center, forming a real threat to acceptor doping of GaN and making p-type doping of GaAsN alloys impossible. The calculated donor levels for AsGa are consistent with luminescence lines around 2.6–2.7 eV in GaN intentionally doped with As. © 2000 American Institute of Physics.
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71.55.Eq III-V semiconductors
78.55.Cr III-V semiconductors

Spatially localized dynamic properties of individual interfaces in semiconducting oxides

Bryan D. Huey and Dawn A. Bonnell

Appl. Phys. Lett. 76, 1012 (2000); http://dx.doi.org/10.1063/1.125923 (3 pages) | Cited 16 times

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Local electronic property variations at individual interfaces have been determined using scanning surface potential microscopy, a variant of atomic force microscopy in conjunction with locally applied electric fields. Micropatterning is used to isolate individual interfaces and position contacts so that biases can be controlled locally. Positional variations in the voltage dependent interface charge and density of states in polycrystalline zinc oxide are determined from surface potential imaging. © 2000 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states

Valence band structure of cubic AlGaN/GaN superlattices

S. C. P. Rodrigues, L. M. R. Scolfaro, J. R. Leite, and G. M. Sipahi

Appl. Phys. Lett. 76, 1015 (2000); http://dx.doi.org/10.1063/1.125924 (3 pages) | Cited 14 times

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The influence of different material parameters, spin-orbit interaction, and strain effects on the valence band structure of cubic AlGaN/GaN superlattices is investigated. One-particle hole state calculations are carried out within the k⋅p theory by means of a full six-band Luttinger-Kohn Hamiltonian in a plane-wave representation. It is shown that the use of distinct values for the Luttinger parameters for the barrier and well regions leads to significant changes in the hole levels, particularly for large Al content. Spin-orbit interaction effects are responsible for strong nonparabolicities due to the light- and split-off-hole bands mixing. Besides, the hole levels are very sensitive to strain effects. Thus, it is demonstrated that these effects cannot be neglected in a realistic description of the valence band structure of these materials. © 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
71.10.Pm Fermions in reduced dimensions (anyons, composite fermions, Luttinger liquid, etc.)
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Atomic force microscope tip-surface behavior under continuous bias or pulsed voltages in noncontact mode

B. Legrand and D. Stiévenard

Appl. Phys. Lett. 76, 1018 (2000); http://dx.doi.org/10.1063/1.125925 (3 pages) | Cited 6 times

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The atomic force microscope is now widely used to oxidize a silicon surface with a continuous bias or pulsed voltages applied between the tip and the silicon surface. The aim of this letter is to study the induced electrostatic effect on the cantilever oscillation in noncontact mode when pulsed voltages are used for nanooxidation. Depending on the relative amplitudes between electrostatic and mechanical excitations, and also on the phase between the pulsed voltages and the mechanical excitation, the cantilever response can dramatically vary. We focus on the details of controlling the feedback loop and exposure conditions in noncontact mode. © 2000 American Institute of Physics.
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68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Mq Oxidation
81.05.Cy Elemental semiconductors
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Optical absorption and anomalous photoconductivity in undoped n-type GaN

S. J. Chung, M. S. Jeong, O. H. Cha, C.-H. Hong, E.-K. Suh, H. J. Lee, Y. S. Kim, and B. H. Kim

Appl. Phys. Lett. 76, 1021 (2000); http://dx.doi.org/10.1063/1.125944 (3 pages) | Cited 18 times

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Photoconductivity and optical absorption measurements were employed to analyze deep levels in undoped n-type GaN films grown on sapphire substrate by metalorganic chemical vapor deposition. At room temperature, the photoconductivity measurement exhibits a broad level at around 1.90 eV. Similarly, the optical absorption spectrum shows a deep level located at 1.87 eV within the band gap, which is best described by a transition from a donor charge-transfer level to the conduction band, according to Lucovsky theory. A persistent photoconductivity whose behavior is distinctive from that of previously reported work for n- or p-type GaN epitaxial films was observed. The photocurrent quenching and decreased dark current in the persistent photoconductivity effect suggest that metastable electron states are formed in the band gap to trap electrons which tunnel out the potential barrier with long recovery time. © 2000 American Institute of Physics.
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71.55.Eq III-V semiconductors
81.05.Ea III-V semiconductors
78.66.Fd III-V semiconductors
73.61.Ey III-V semiconductors
72.80.Ey III-V and II-VI semiconductors
73.50.Pz Photoconduction and photovoltaic effects
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Determination of the concentration of hot-carrier-induced bulk defects in laser-recrystallized polysilicon thin film transistors

T. M. Brown and P. Migliorato

Appl. Phys. Lett. 76, 1024 (2000); http://dx.doi.org/10.1063/1.125926 (3 pages) | Cited 8 times

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We present a method to investigate hot carrier induced defects in laser recrystallized polysilicon thin film transistors, based on the use of a structure with front and back gate and the analysis of the off current. The maximum process temperature for these devices was 425 °C. We find that both positive and negative VGS produce similar degradation of the characteristics and the main effect is bulk, rather than interface, state creation. The changes in the I–V characteristics are accounted for by an increase of the dangling bond concentration, which is obtained as a fitting parameter, giving a good agreement between experiment and simulation. © 2000 American Institute of Physics.
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85.30.Tv Field effect devices
73.50.Fq High-field and nonlinear effects
73.61.Cw Elemental semiconductors

Intra-valence band photocurrent spectroscopy of self-assembled Ge dots in Si

C. Miesner, O. Röthig, K. Brunner, and G. Abstreiter

Appl. Phys. Lett. 76, 1027 (2000); http://dx.doi.org/10.1063/1.125927 (3 pages) | Cited 29 times

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Intra-valence band photocurrent investigations of self-assembled Ge dots in Si are reported. Boron-doped Ge dots of about 70 nm diameter and 6.5 nm height are deposited by molecular beam epitaxy in the Stranski–Krastanov growth mode within the intrinsic region of a p+-i-p+ Si structure. For a broad excitation wavelength range between about 2 μm (620 meV) and 6 μm (207 meV), interlevel photocurrent is observed in normal incidence and waveguide geometry. The absorption is attributed to transitions from hole states bound in the Ge dots to continuum states. The photocurrent can be measured up to T = 100 K without any significant decrease of the responsivity. © 2000 American Institute of Physics.
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73.50.Pz Photoconduction and photovoltaic effects
73.61.Cw Elemental semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Cy Elemental semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Electronic states and band alignment in GalnNAs/GaAs quantum-well structures with low nitrogen content

M. Hetterich, M. D. Dawson, A. Yu. Egorov, D. Bernklau, and H. Riechert

Appl. Phys. Lett. 76, 1030 (2000); http://dx.doi.org/10.1063/1.125928 (3 pages) | Cited 127 times

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We investigate the electronic states in strained Ga0.62In0.38N0.015As0.985/GaAs multiple- quantum-well structures using photoluminescence and (polarized) photoluminescence excitation measurements at low temperature. From a theoretical fit to the experimental data, a type-I band alignment for the heavy holes with a strained conduction-band offset ratio of about 80% is obtained, while the light holes show an approximately flat band alignment. Additionally, our results suggest an increased effective electron mass in GaInNAs, possibly due to the interaction of the conduction band with nitrogen-related resonant states, an observation prospectively of benefit for GaInNAs-based diode lasers. © 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
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

An analysis of temperature dependent piezoelectric Franz–Keldysh effect in AlGaN

Y. T. Hou, K. L. Teo, M. F. Li, Kazuo Uchida, Hiroki Tokunaga, Nakao Akutsu, and Koh Matsumoto

Appl. Phys. Lett. 76, 1033 (2000); http://dx.doi.org/10.1063/1.125929 (3 pages) | Cited 12 times

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Strong Franz–Keldysh oscillations near the band gap of AlGaN are observed in the contactless electroreflectance (CER) studies of a GaN/InGaN/AlGaN multilayer structure. The line shape analysis of the CER spectra at different temperatures provides an accurate determination of the AlGaN band gap energies and the built-in electric fields. Using the existing data of the thermal expansion coefficients of GaN and sapphire, and the piezoelectric constants of AlGaN, the temperature dependence of the electric field is estimated and is in good agreement with the experimental results between 15 and 300 K. We attribute such electric field to the piezoelectric strain effect. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
77.65.Ly Strain-induced piezoelectric fields
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
78.20.Jq Electro-optical effects
65.40.De Thermal expansion; thermomechanical effects

Room-temperature observation of the Coulomb blockade effects in Al two-terminal diodes fabricated using a focused ion-beam nanoparticle process

T. W. Kim, S. O. Kang, D. C. Choo, and J. H. Shim

Appl. Phys. Lett. 76, 1036 (2000); http://dx.doi.org/10.1063/1.125930 (3 pages) | Cited 5 times

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Al two-terminal diodes were fabricated on a basis of an artificial pattern formation method using focused ion-beam (FIB) techniques. The results of current–voltage and conductance–voltage measurements at room temperature showed the Coulomb staircase and the Coulomb blockade effects, respectively. The Coulomb blockade effects originate from the many nanoparticles created by the defects due to the Ga+ ion beam. These results indicate that Al two-terminal diodes fabricated by using the FIB system hold promise for potential applications in single-electron transistors operating at room temperature. © 2000 American Institute of Physics.
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73.23.Hk Coulomb blockade; single-electron tunneling

Temperature-dependent tunneling through thermally grown SiO2 on n-type 4H– and 6H–SiC

Richard Waters and Bart Van Zeghbroeck

Appl. Phys. Lett. 76, 1039 (2000); http://dx.doi.org/10.1063/1.125931 (3 pages) | Cited 7 times

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The temperature dependence of field emission through thermally grown silicon dioxide (SiO2) on n-type 4H and 6H silicon carbide (SiC) substrates is reported. Room-temperature SiO2/SiC barrier heights, ΦB, of 1.92 and 2.12 V are extracted for the 4H– and 6H–SiC samples, respectively, using a Fowler–Nordheim analysis. Barrier heights of 2.2 and 2.4 V along with a linear temperature-dependent barrier height lowering, ΔΦB/ΔT, of 2.4 and 2.0 mV/K for 4H– and 6H–SiC are extracted using an alternative analytical expression for tunneling from semiconducting substrates derived previously. In both analyses, the temperature-dependent flatband voltage, using the measured room-temperature value, was included. © 2000 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.30.Tv Field effect devices

Many-body effects on excitons properties in GaN/AlGaN quantum wells

Giampiero Traetta, Roberto Cingolani, Aldo Di Carlo, Fabio Della Sala, and Paolo Lugli

Appl. Phys. Lett. 76, 1042 (2000); http://dx.doi.org/10.1063/1.125932 (3 pages) | Cited 22 times

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The many-body effects on excitons properties in GaN/AlGaN quantum wells are theoretically investigated by using a Green’s function model and the electron and hole wave functions calculated either in the envelope function approximation or in the frame of a self-consistent tight-binding model. We show that the built-in field induced by the piezoelectric and spontaneous polarization charge causes a reduction of the exciton binding energy and of the absorption coefficient well below the values expected for the quantum well with flat band. At high carrier concentrations, the many-body screening prevails over the screening of the built-in electric field, causing complete exciton bleaching at typical densities of the order of 1012 cm−2. © 2000 American Institute of Physics.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.35.Gg Exciton-mediated interactions
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
77.65.Ly Strain-induced piezoelectric fields
77.22.Ej Polarization and depolarization
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency

Investigation of vertical transport in n-GaN films grown by molecular beam epitaxy using Schottky barrier diodes

M. Misra, A. V. Sampath, and T. D. Moustakas

Appl. Phys. Lett. 76, 1045 (2000); http://dx.doi.org/10.1063/1.125933 (3 pages) | Cited 19 times

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In this letter, the lateral and vertical transport in lightly doped n−-GaN films, grown by plasma assisted molecular beam epitaxy, were investigated in order to explore the role of electron scattering by charged dislocations. Lateral transport constants were determined by Hall effect measurements on n−-GaN films. The doping concentration and mobility of the investigated films was 1–2×1017 cm−3 and 150–200 cm2/V s, respectively. Vertical transport was studied by etching mesa structures and forming Schottky barrier diodes. The diodes exhibit near ideal forward current–voltage characteristics with reverse saturation current densities in the 1–10×10−9  A cm−2 range. The doping concentrations as well as the barrier height of the diodes were determined from capacitance–voltage measurements to be 8–9×1016 cm−3 and 0.95–1.0 V, respectively. The analysis of the reverse saturation current, using the diffusion theory, leads to vertical mobility values of 950 cm2/V s. The significant increase in mobility for vertical transport is attributed to reduction in scattering by charged dislocations. © 2000 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.Hi Molecular, atomic, ion, and chemical beam epitaxy
85.30.Kk Junction diodes
81.05.Ea III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.50.Bk General theory, scattering mechanisms
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
81.65.Cf Surface cleaning, etching, patterning
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