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14 Aug 2000

Volume 77, Issue 7, pp. 921-1064

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Yellow luminescence and Fermi level pinning in GaN layers

I. Shalish, L. Kronik, G. Segal, Yoram Shapira, M. Eizenberg, and J. Salzman

Appl. Phys. Lett. 77, 987 (2000); http://dx.doi.org/10.1063/1.1288813 (3 pages) | Cited 13 times

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A correlation between Fermi level pinning and yellow luminescence in Pt/n-GaN junctions has been studied using Schottky barrier measurements by internal photoemission spectroscopy and complementary deep level spectroscopies. The results show that illumination by photons with energies in the yellow luminescence range causes an unpinning of the interface Fermi level, accompanied by a significant increase of the Schottky barrier height from ∼1 to ∼1.9 eV. This strongly suggests the presence of acceptor states related to the yellow luminescence at the Pt/GaN interface. These states are charged in equilibrium and pin the interface Fermi level but can be optically discharged, resulting in a nearly unpinned interface. © 2000 American Institute of Physics.
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78.55.Cr III-V semiconductors
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
73.40.Ns Metal-nonmetal contacts
73.30.+y Surface double layers, Schottky barriers, and work functions
78.70.-g Interactions of particles and radiation with matter
73.20.At Surface states, band structure, electron density of states

Polarization-induced electron populations

B. K. Ridley

Appl. Phys. Lett. 77, 990 (2000); http://dx.doi.org/10.1063/1.1288817 (3 pages) | Cited 18 times

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Electron populations induced by spontaneous and piezoelectric polarization in semiconductor heterostructures can be estimated simply by using elementary electrostatic theory. The method is illustrated for the AlGaN/GaN system in which the AlGaN barrier is either undoped, or doped n type, and the effect of a GaN overlayer is described. © 2000 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
77.22.Ej Polarization and depolarization
77.65.-j Piezoelectricity and electromechanical effects
73.61.Ey III-V semiconductors

Hydrogen effects on ZnSe/GaAs interface: A photoreflectance study

E. D. Sim, J. H. Song, S. K. Chang, and H. K. Kim

Appl. Phys. Lett. 77, 993 (2000); http://dx.doi.org/10.1063/1.1288814 (3 pages) | Cited 3 times

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ZnSe/GaAs heteroepitaxial structures were prepared by metalorganic chemical vapor deposition with the use of thermal cleaning treatments at varying hydrogen flow rates in preparing the substrate. The photoreflectance spectra for the samples prepared revealed Franz–Keldysh oscillation (FKO) signals with the superimposition of free exciton transition features. The FKO signals changed depending on the hydrogen flow rate while the exciton transition features remained unchanged. Fitting through Aspnes’ and Franz–Keldysh’s model showed that the built-in electric field at the interface increased as the hydrogen flow rate decreased. These results imply that the hydrogen flow rate in the course of thermal etching plays a crucial role in the change of the energy-band profile at the interface. © 2000 American Institute of Physics.
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78.66.Hf II-VI semiconductors
78.66.Fd III-V semiconductors
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Ea III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning
81.15.Kk Vapor phase epitaxy; growth from vapor phase
71.35.-y Excitons and related phenomena

Reconstruction of an InP(001) surface grown by metalorganic vapor phase epitaxy in atmospheric hydrogen environment

T. Kawamura, Y. Watanabe, Y. Utsumi, K. Uwai, J. Matsui, Y. Kagoshima, Y. Tsusaka, and S. Fujikawa

Appl. Phys. Lett. 77, 996 (2000); http://dx.doi.org/10.1063/1.1289034 (3 pages) | Cited 1 time

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A reconstructed surface of InP (001) substrate, grown by metalorganic vapor phase epitaxy under atmospheric hydrogen environment, is investigated by using grazing incident x-ray diffraction. Fractional-order diffractions of (n/2 m) were observed, showing the existence of a (2×1) domain on the surface. Calculations based on the P-dimer model suggest that there are P dimers whose bonding is parallel to the [math10] direction and indium displacement in the second layer. © 2000 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.05.Ea III-V semiconductors
68.55.-a Thin film structure and morphology

Transport and quantum electron mobility in the modulation Si δ-doped pseudomorphic GaAs/In0.2Ga0.8As/Al0.2Ga0.8As quantum well grown by metalorganic vapor phase epitaxy

Adam Babiński, J. Siwiec-Matuszyk, J. M. Baranowski, G. Li, and C. Jagadish

Appl. Phys. Lett. 77, 999 (2000); http://dx.doi.org/10.1063/1.1289035 (3 pages) | Cited 2 times

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A study of transport and quantum mobility of electrons in two-dimensional electron gas (2DEG) in the modulation Si δ-doped pseudomorphic GaAs/In0.2Ga0.8As/Al0.2Ga0.8As quantum well (QW) grown by metalorganic vapor phase epitaxy is presented. Well-resolved Shubnikov–de Haas oscillations of the magnetoresistivity observed at T = 4.2 K suggest that the 2DEG with high electron mobility (μt ≈ 46 000 cm2/V s) formed in the QW with no significant parallel conduction. A persistent photoconductivity effect resulted in an increase in electron sheet density. An increase of transport and quantum mobilities up to the onset of the second subband occupancy was observed. Further illumination resulted in a decrease of both mobilities. Strong dependence of the quantum mobility on the thermal history of the investigated sample was attributed to the effect of actual distribution of ionized centers in the sample. © 2000 American Institute of Physics.
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73.61.Ey III-V semiconductors
81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Pz Photoconduction and photovoltaic effects
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Spatial pattern formation of optically excited carriers in photoconductive switches

M. Bieler, G. Hein, K. Pierz, U. Siegner, and M. Koch

Appl. Phys. Lett. 77, 1002 (2000); http://dx.doi.org/10.1063/1.1289037 (3 pages) | Cited 9 times

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We have spatially resolved the photoluminescence patterns emitted from a GaAs/Al0.3Ga0.7As quantum well after femtosecond laser excitation for different electric bias fields applied in the plane of the well. These patterns demonstrate substantially different electron–hole dynamics across the excitation laser spot. The density dependence of screening combines with the lateral variation of the carrier density to produce the observed effects. These results prove that the spatial variation of the carrier dynamics is to be taken into account for the optimization of photoconductive switches as ultrafast voltage pulse sources or THz emitters. © 2000 American Institute of Physics.
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85.60.-q Optoelectronic devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
73.61.Ey III-V semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
73.50.Pz Photoconduction and photovoltaic effects
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Time-resolved photoluminescence of GaN/Al0.5Ga0.5N quantum wells

J. C. Harris, T. Someya, S. Kako, K. Hoshino, and Y. Arakawa

Appl. Phys. Lett. 77, 1005 (2000); http://dx.doi.org/10.1063/1.1289041 (3 pages) | Cited 15 times

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We report photoluminescence (PL) and time-resolved PL measurements of GaN/AlxGa1−xN multiple quantum wells with barriers of high aluminum content, x = 0.5. In wells of width 1–2 nm, low temperature recombination appears to be dominated by radiative processes with lifetimes ∼0.5 ns. Dependence of lifetime on emission energy is very small compared to InGaN quantum wells, indicating that carrier localization is very slight and interface quality is high. In 4 nm wells, PL emission at an energy below the bulk GaN band gap and long recombination lifetimes result from the polarization field across the wells. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Electron cyclotron resonance plasma etching of GaSb-based alloys

R. U. Ahmad, G. Nagy, R. M. Osgood, G. W. Turner, M. J. Manfra, and J. W. Chludzinski

Appl. Phys. Lett. 77, 1008 (2000); http://dx.doi.org/10.1063/1.1289058 (3 pages) | Cited 1 time

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Electron cyclotron resonance plasma etching is used to fabricate submicrometer-scale GaInAsSb/AlGaAsSb multiple-quantum-well structures. Smooth and anisotropic features at low substrate bias were obtained under appropriate conditions. The etch quality was investigated with photoluminescence spectroscopy; luminescence data from the etched features agree well with a model that assumes a low-damage etching process. © 2000 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.05.Ea III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)

Current conduction mechanism of Si/Ti-based Ohmic contacts to n-GaN

Dae-Woo Kim and Hong Koo Baik

Appl. Phys. Lett. 77, 1011 (2000); http://dx.doi.org/10.1063/1.1289057 (3 pages) | Cited 17 times

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We have investigated the Ohmic contact formation mechanism of Si/Ti-based contacts to n-GaN. The Si/Ti contact system was selected because Ti silicides have a low work function and also Si has been used widely as an n-type dopant. Our experimental results show that the Ohmic behavior of Si/Ti-based contacts were attributed to the low barrier height of the Ti silicide/GaN interface. The contact resistance of Si/Ti-based Ohmic contacts decreased exponentially with the measuring temperature. It can be concluded that current flows over the low barrier height by thermionic emission. © 2000 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
68.35.Fx Diffusion; interface formation
85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Ny Chemical interdiffusion; diffusion barriers
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
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