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Journal ArticleDOI

Scattering of electrons at threading dislocations in GaN

04 Jun 1998-Journal of Applied Physics (American Institute of Physics)-Vol. 83, Iss: 7, pp 3656-3659
TL;DR: In this paper, a model to explain the observed low transverse mobility in GaN by scattering of electrons at charged dislocation lines is proposed and the statistics of trap occupancy at different doping levels are investigated.
Abstract: A model to explain the observed low transverse mobility in GaN by scattering of electrons at charged dislocation lines is proposed. Filled traps along threading dislocation lines act as Coulomb scattering centers. The statistics of trap occupancy at different doping levels are investigated. The theoretical transverse mobility from Coulomb scattering at charged traps is compared to experimental data. Due to the repulsive potential around the charged dislocation lines, electron transport parallel to the dislocations is unaffected by the scattering at charged dislocation lines.
Citations
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Journal ArticleDOI
TL;DR: In this article, the authors investigated the role of spontaneous and piezoelectric polarization on the carrier confinement at GaN/AlGaN and AlGaN/GaN interfaces.
Abstract: Carrier concentration profiles of two-dimensional electron gases are investigated in wurtzite, Ga-face AlxGa1−xN/GaN/AlxGa1−xN and N-face GaN/AlxGa1−xN/GaN heterostructures used for the fabrication of field effect transistors. Analysis of the measured electron distributions in heterostructures with AlGaN barrier layers of different Al concentrations (0.15

2,581 citations

Journal ArticleDOI
TL;DR: The role of extended and point defects, and key impurities such as C, O, and H, on the electrical and optical properties of GaN is reviewed in this article, along with the influence of process-induced or grown-in defects and impurities on the device physics.
Abstract: The role of extended and point defects, and key impurities such as C, O, and H, on the electrical and optical properties of GaN is reviewed. Recent progress in the development of high reliability contacts, thermal processing, dry and wet etching techniques, implantation doping and isolation, and gate insulator technology is detailed. Finally, the performance of GaN-based electronic and photonic devices such as field effect transistors, UV detectors, laser diodes, and light-emitting diodes is covered, along with the influence of process-induced or grown-in defects and impurities on the device physics.

1,693 citations

Journal ArticleDOI
14 Aug 1998-Science
TL;DR: In this paper, high efficiency light-emitting diodes emitting amber, green, blue, and ultraviolet light have been obtained through the use of an InGaN active layer instead of a GaN active layers.
Abstract: REVIEW High-efficiency light-emitting diodes emitting amber, green, blue, and ultraviolet light have been obtained through the use of an InGaN active layer instead of a GaN active layer. The localized energy states caused by In composition fluctuation in the InGaN active layer are related to the high efficiency of the InGaN-based emitting devices. The blue and green InGaN quantum-well structure light-emitting diodes with luminous efficiencies of 5 and 30 lumens per watt, respectively, can be made despite the large number of threading dislocations (1 x 10(8) to 1 x 10(12) cm-2). Epitaxially laterally overgrown GaN on sapphire reduces the number of threading dislocations originating from the interface of the GaN epilayer with the sapphire substrate. InGaN multi-quantum-well structure laser diodes formed on the GaN layer above the SiO2 mask area can have a lifetime of more than 10,000 hours. Dislocations increase the threshold current density of the laser diodes.

1,675 citations

Journal ArticleDOI
TL;DR: In this paper, a combination of high resolution x-ray diffraction, atomic force microscopy, Hall effect, and capacitance-voltage profiling measurements is used to calculate the polarization induced sheet charge bound at the AlGaN/GaN interfaces.
Abstract: Two dimensional electron gases in Al x Ga 12x N/GaN based heterostructures, suitable for high electron mobility transistors, are induced by strong polarization effects. The sheet carrier concentration and the confinement of the two dimensional electron gases located close to the AlGaN/GaN interface are sensitive to a large number of different physical properties such as polarity, alloy composition, strain, thickness, and doping of the AlGaN barrier. We have investigated these physical properties for undoped and silicon doped transistor structures by a combination of high resolution x-ray diffraction, atomic force microscopy, Hall effect, and capacitance‐voltage profiling measurements. The polarization induced sheet charge bound at the AlGaN/GaN interfaces was calculated from different sets of piezoelectric constants available in the literature. The sheet carrier concentration induced by polarization charges was determined

1,439 citations

Journal ArticleDOI
TL;DR: The wet etching of GaN, AlN, and SiC is reviewed in this paper, including conventional etching in aqueous solutions, electrochemical etch in electrolytes and defect-selective chemical etched in molten salts.
Abstract: The wet etching of GaN, AlN, and SiC is reviewed including conventional etching in aqueous solutions, electrochemical etching in electrolytes and defect-selective chemical etching in molten salts. The mechanism of each etching process is discussed. Etching parameters leading to highly anisotropic etching, dopant-type/bandgap selective etching, defect-selective etching, as well as isotropic etching are discussed. The etch pit shapes and their origins are discussed. The applications of wet etching techniques to characterize crystal polarity and defect density/distribution are reviewed. Additional applications of wet etching for device fabrication, such as producing crystallographic etch profiles, are also reviewed.

680 citations

References
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Journal ArticleDOI
TL;DR: In this article, the authors investigated native defects and native defect impurity complexes as candidate sources for the yellow luminescence in GaN and found strong evidence that the Ga vacancy (VGa) is responsible.
Abstract: We have investigated native defects and native defect‐impurity complexes as candidate sources for the yellow luminescence in GaN. Using state‐of‐the‐art first‐principles calculations, we find strong evidence that the Ga vacancy (VGa) is responsible. The dependence of the VGa formation energy on Fermi level explains why the yellow luminescence is observed only in n‐type GaN. The VGa defect level is a deep acceptor state, consistent with recent pressure experiments. Finally we show that the formation of VGa is enhanced by the creation of complexes between VGa and donor impurities.

1,032 citations

Journal ArticleDOI
TL;DR: In this article, the electrical, optical, and structural properties of light emitting diodes (LEDs) fabricated from the III-V nitride material system have been studied.
Abstract: The electrical, optical, and structural properties of light emitting diodes (LEDs) fabricated from the III–V nitride material system have been studied. LEDs with external quantum efficiencies as high as 4% were characterized by transmission electron microscopy and found to contain dislocation densities in excess of 2×1010 cm−2. A comparison to other III–V arsenide and phosphide LEDs shows that minority carries in GaN‐based LEDs are remarkably insensitive to the presence of structural defects. Dislocations do not act as efficient nonradiative recombination sites in nitride materials. It is hypothesized that the benign character of dislocations arises from the ionic nature of bonding in the III–V nitrides.

952 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown that the simple theory of lattice scattering alone cannot explain the temperature dependence of the resistivity of germanium semiconductors and that another probable source of resistance is scattering by ionized impurity centers.
Abstract: Experiments by Lark-Horovitz and collaborators on the Hall effect and resistivity of germanium semiconductors have shown that the simple theory of lattice scattering alone cannot explain the temperature dependence of the resistivity. Another probable source of resistance is scattering by ionized impurity centers. This resistance can be calculated by using the Rutherford scattering formula. Evaluation of the collision terms in the Lorentz-Boltzmann equation of state is made by assuming that scattering of an electron by one ion is approximately independent of all other ions. This results in a resistivity given by (in ohm cm): $\ensuremath{\rho}=2.11\ifmmode\times\else\texttimes\fi{}{10}^{2}{\ensuremath{\kappa}}^{\ensuremath{-}2}{T}^{\ensuremath{-}\frac{3}{2}}\mathrm{ln}{1+36{\ensuremath{\kappa}}^{2}{d}^{2}{(\mathrm{kT})}^{2}{e}^{\ensuremath{-}4}}$ where $d$ is half the average distance between impurity ions and $\ensuremath{\kappa}$ the dielectric constant of the semiconductor.

712 citations

Journal ArticleDOI
TL;DR: In this paper, the theory of dislocation density measurement from rocking curves is extended to the case of (001) zinc-blende semiconductors, and it is shown that the measurement of several ( hkl ) rocking curve widths with a particular X-ray wavelength allows the calculation of the dislocations density by two independent techniques, thus allowing for a check of self-consistency.

426 citations

Journal ArticleDOI
TL;DR: In this paper, a simple model was proposed to identify dislocation acceptors with dangling unpaired electrons on the edge of the extra atomic plane of a dislocation having some edge component.
Abstract: Dislocations have a large effect on the electrical properties of germanium. Experiments show that dislocations act as acceptor centres. This paper discusses a simple model (due to W. Shockley) which identifies dislocation acceptors with the dangling unpaired electrons on the edge of the extra atomic plane of a dislocation having some edge component. In n-type germanium the line of acceptors along a dislocation accepts electrons and becomes negatively charged. The electrostatic energy in the resulting space charge region is found and shown to be a dominant factor in determining the occupation of dislocation acceptors. Formulas are given for the temperature variation of the average electron concentration in n-type material that has been lightly deformed by plastic bending. Experiments are suggested to test the theory and determine exactly the energy level of the dislocation acceptors.

391 citations