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25 Jun 2001

Volume 78, Issue 26, pp. 4065-4199

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Band gap of amorphous and well-ordered Al2O3 on Ni3Al(100)

I. Costina and R. Franchy

Appl. Phys. Lett. 78, 4139 (2001); http://dx.doi.org/10.1063/1.1380403 (3 pages) | Cited 30 times

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The vibrational and electronic properties of amorphous and well-ordered alumina formed on Ni3Al(100) were investigated using high-resolution electron energy loss spectroscopy. The structure of well-ordered alumina was analyzed by low-energy electron diffraction. The amorphous Al2O3 films are prepared by adsorption of O2 at room temperature, while the well-ordered Al2O3 are obtained by direct oxidation of Ni3Al at 1150 K. The band gap energy is ∼3.2 and ∼4.3 eV for amorphous alumina and well-ordered alumina thin films respectively. The lowering of the band gap with respect to the bulk value of Al2O3 is associated with defect-induced states located in the band gap. © 2001 American Institute of Physics.
Show PACS
71.23.-k Electronic structure of disordered solids
68.47.Gh Oxide surfaces
68.55.-a Thin film structure and morphology
71.20.Ps Other inorganic compounds
71.55.Ht Other nonmetals
71.55.Jv Disordered structures; amorphous and glassy solids
79.20.Uv Electron energy loss spectroscopy
68.49.Jk Electron scattering from surfaces
68.43.Mn Adsorption kinetics
81.65.Mq Oxidation
63.20.-e Phonons in crystal lattices
63.50.-x Vibrational states in disordered systems

Positron annihilation study of Pd contacts on impurity-doped GaN

Jong-Lam Lee, Jong Kyu Kim, Marc H. Weber, and Kelvin G. Lynn

Appl. Phys. Lett. 78, 4142 (2001); http://dx.doi.org/10.1063/1.1380395 (3 pages) | Cited 6 times

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Pd contacts on both n-type and p-type GaN were studied using positron annihilation spectroscopy, and the results were used to interpret the role of Ga vacancies on the band bending below the contacts. The concentration of Ga vacancy in Si-doped GaN was higher than that in the Mg-doped one. In Si-doped GaN, implanted positrons were annihilated at the nearer surface region and the interface of Pd/n-type GaN was detected by positrons clearly shifted toward the surface of Pd. This suggests that Ga vacancies could act as an interface state, pinning the Fermi level at the interface of Pd with GaN, leading to the production of a negative electric field below the interface. © 2001 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
73.20.Hb Impurity and defect levels; energy states of adsorbed species
78.70.Bj Positron annihilation
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Dependence of GaN polarity on the parameters of the buffer layer grown by molecular beam epitaxy

D. Huang, P. Visconti, K. M. Jones, M. A. Reshchikov, F. Yun, A. A. Baski, T. King, and H. Morkoç

Appl. Phys. Lett. 78, 4145 (2001); http://dx.doi.org/10.1063/1.1380399 (3 pages) | Cited 35 times

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The polarity of GaN films grown using GaN and AlN buffer layers on sapphire substrates by molecular beam epitaxy were investigated by atomic force microscopy, hot wet chemical etching, and reflection high-energy electron diffraction. We found that the GaN films grown on high temperature AlN (>890 °C) and GaN (770–900 °C) buffer layers invariably show Ga and N polarity, respectively. However, the films grown using low temperature (∼500 °C) buffer layers, either GaN or AlN, could have either Ga or N polarity, depending on the growth rate of the buffer layer. © 2001 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
68.37.Ps Atomic force microscopy (AFM)
81.65.Cf Surface cleaning, etching, patterning

Emission wavelength control by potential notch in type-II InAs/GaSb/AlSb intersubband light-emitting structures

K. Ohtani, H. Sakuma, and H. Ohno

Appl. Phys. Lett. 78, 4148 (2001); http://dx.doi.org/10.1063/1.1381034 (3 pages)

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A potential notch in the well region is used to control the emission wavelength of type-II InAs/GaSb/AlSb intersubband light-emitting structures. Intersubband absorption measurements are performed to evaluate the subband structure of the active layers and are compared with theory. Type-II quantum cascade structures using these active layers are fabricated and midinfrared intersubband electroluminescence is observed. Calculation indicates that the active layer structure can emit electromagnetic waves in the THz region without employing a wide alloy well. © 2001 American Institute of Physics.
Show PACS
85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.67.De Quantum wells

Evidence of isoelectronic traps in molecular beam epitaxy grown Zn1−xBexSe: Temperature- and pressure-dependent photoluminescence studies

Bosang S. Kim, Igor L. Kuskovsky, C. Tian, Irving P. Herman, G. F. Neumark, S. P. Guo, and M. C. Tamargo

Appl. Phys. Lett. 78, 4151 (2001); http://dx.doi.org/10.1063/1.1381039 (3 pages) | Cited 3 times

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We have studied undoped Zn1−xBexSe alloys grown by molecular beam epitaxy by photoluminescence (PL) as a function of temperature and pressure. We suggest that there are isoelectronic excitonic traps in this material. The binding energy of the isoelectronic bound excitons is deep, between 40 and 50 meV. We have also shown that the temperature and pressure dependences of the Zn1−xBexSe PL are close to those of ZnSe. From this we conclude that the dominant excitonic recombination is of an “effective mass” type. © 2001 American Institute of Physics.
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78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
71.55.Gs II-VI semiconductors
71.35.Gg Exciton-mediated interactions
81.05.Dz II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Integrated porous-silicon light-emitting diodes: A fabrication process using graded doping profiles

G. Barillaro, A. Diligenti, F. Pieri, F. Fuso, and M. Allegrini

Appl. Phys. Lett. 78, 4154 (2001); http://dx.doi.org/10.1063/1.1381572 (3 pages) | Cited 5 times

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A fabrication process, compatible with an industrial bipolar+complementary metal–oxide–semiconductor (MOS)+diffusion MOS technology, has been developed for the fabrication of efficient porous-silicon-based light-emitting diodes. The electrical contact is fabricated with a double n+/p doping, achieving a high current injection efficiency and thus lower biasing voltages. The anodization is performed as the last step of the process, thus reducing potential incompatibilities with industrial processes. The fabricated devices show yellow-orange electroluminescence, visible with the naked eye in room lighting. A spectral characterization of light emission is presented and briefly discussed. © 2001 American Institute of Physics.
Show PACS
85.60.Jb Light-emitting devices
81.05.Rm Porous materials; granular materials
61.72.uf Ge and Si
85.40.Ry Impurity doping, diffusion and ion implantation technology
85.60.-q Optoelectronic devices
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