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9 Jul 2001

Volume 79, Issue 2, pp. 145-277

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Nitrogen-related complexes in gallium arsenide

J. E. Lowther, S. K. Estreicher, and H. Temkin

Appl. Phys. Lett. 79, 200 (2001); http://dx.doi.org/10.1063/1.1383280 (3 pages) | Cited 9 times

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A first-principles pseudopotential method has been used to study some potentially important metastable defects in N-doped GaAs. Formation energies have been obtained and related to those of As and Ga vacancies in the intrinsic material. Of the structures considered, two are identified that crucially depend on overall material stoichiometry. These are N on a Ga site (NGa) or a NN dimer on an As site (NNAs). NGa has a partly shallow energy-level structure with a fully occupied level lying near the valence-band edge, whereas NNAs has localized character with a midgap deep level. Both defects may be responsible for the onset of a reduction in the apparent band gap that has been recently observed in heavily N-doped GaAs prior to alloying. © 2001 American Institute of Physics.
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71.55.Eq III-V semiconductors
61.72.J- Point defects and defect clusters
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
61.66.Bi Elemental solids
61.66.Dk Alloys

Solving the structural model for the Si(001)–In(4×3) surface

T. M. Schmidt, J. L. P. Castineira, and R. H. Miwa

Appl. Phys. Lett. 79, 203 (2001); http://dx.doi.org/10.1063/1.1383275 (3 pages) | Cited 8 times

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The atomic geometry, energetic, and scanning tunneling microscopy (STM) simulations of the In-induced Si(001)-(4×3) surface have been investigated using first-principles total energy calculations. We have studied three distinct (4×3) structural models, which have been proposed based on STM and x-ray diffraction experiments. The energetic stability calculations indicate that the (4×3) model formed by In–Si–In mixed trimer is the most stable structure. In addition, we have simulated the STM images (for occupied states) of these three models. Our STM image for the In–Si–In mixed trimer structure presents a good agreement with the experimentally observed single central protrusion localized on the top-layer Si atom. Also, the calculated equilibrium atomic geometry of the In–Si–In mixed trimer model presents a good agreement with the experimentally obtained x-ray diffraction results. The other two proposed models are energetically less favorable by as much as 0.2 eV/(1×1) compared to the mixed trimer model. © 2001 American Institute of Physics.
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68.43.Fg Adsorbate structure (binding sites, geometry)
81.05.Cy Elemental semiconductors
71.15.Nc Total energy and cohesive energy calculations
68.35.Md Surface thermodynamics, surface energies
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.35.B- Structure of clean surfaces (and surface reconstruction)

High temperature semiconducting characteristics of magnesium-doped α-Al2O3 single crystals

M. Tardío, R. Ramírez, R. González, Y. Chen, and M. R. Kokta

Appl. Phys. Lett. 79, 206 (2001); http://dx.doi.org/10.1063/1.1384481 (3 pages) | Cited 5 times

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In the temperature interval 300–773 K, ac and dc electrical measurements show a phenomenally large enhancement of the electrical conductivity of otherwise excellent insulator Al2O3 crystals when doped with magnesium impurities. The conductivity increases linearly with the concentration of hole-trapped [Mg]0 centers and is four times higher in the direction parallel to the crystallographic c axis than in the perpendicular direction. The conductivity activation energy is 0.68 eV, independent of both [Mg]0 content and crystallographic orientation. Electroluminescence experiments indicate that holes are the majority carriers. These results favor the small-polaron-motion mechanism. © 2001 American Institute of Physics.
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72.80.Jc Other crystalline inorganic semiconductors
78.60.Fi Electroluminescence
72.20.Fr Low-field transport and mobility; piezoresistance
71.55.Ht Other nonmetals

Nonlinear current–voltage relations in polycrystalline perovskite manganites ceramics

John Philip and T. R. N. Kutty

Appl. Phys. Lett. 79, 209 (2001); http://dx.doi.org/10.1063/1.1384474 (3 pages) | Cited 11 times

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Highly nonlinear current–voltage (J∝Eα) relations with voltage-limiting characteristics are observed for Mg-doped lanthanum calcium manganite polycrystalline ceramics with nonlinearity coefficient, α = 2–9 at low-electric-field strengths of 2–5 V/mm, below magnetic transition temperatures. The current density increases with external magnetic field, so that magnetically tunable low-voltage varistors are realized. The α increases on annealing at 1375 K in atmospheres of lower pO2, and becomes more pronounced with decreasing grain size, indicating that nonlinear behavior is related to the outdiffusion of oxygen through the grain-boundary-layer regions. The increasing deficiency in Mn3+/Mn4+ pairs reduces the hole-hopping probability leading to insulating barriers in the grain-boundary-layer regions. The barrier height is lowered by the external electric field, facilitating the charge-carrier movement between the grains. Since the conduction is due to spin-polarized tunneling, the external magnetic field increases the current. © 2001 American Institute of Physics.
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75.47.Gk Colossal magnetoresistance
61.72.Cc Kinetics of defect formation and annealing
61.72.Mm Grain and twin boundaries

Role of holes in the isotope effect and mechanisms for the metal–oxide–semiconductor device degradation

Zhi Chen, Pradeep Garg, Vijay Singh, and Sundar Chetlur

Appl. Phys. Lett. 79, 212 (2001); http://dx.doi.org/10.1063/1.1384900 (3 pages) | Cited 2 times

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An experiment that incorporates the deuterium isotope effect into the “hole trapping and electron filling” scenario in silicon metal–oxide–semiconductor (MOS) devices is presented. It is suggested that Lai’s physical model is only partially true in order to explain all of the observed MOS device degradation phenomena. The isotope effect is exclusively due to hot electrons, not hot holes. Holes might break the Si–O bonds to generate interface traps at VG near VT. The dominant degradation mechanism is the electron-stimulated Si–H bond breaking, although electron trapping also plays a role in degradation. © 2001 American Institute of Physics.
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85.30.Tv Field effect devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Formation mechanism of V defects in the InGaN/GaN multiple quantum wells grown on GaN layers with low threading dislocation density

H. K. Cho, J. Y. Lee, G. M. Yang, and C. S. Kim

Appl. Phys. Lett. 79, 215 (2001); http://dx.doi.org/10.1063/1.1384906 (3 pages) | Cited 52 times

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V-defect formation of the InxGa1−xN/GaN multiple quantum wells (MQWs) grown on GaN layers with different threading dislocation (TD) densities was investigated. From cross-sectional transmission electron microscopy, we found that all V defects are not always connected with TDs at their bottom. By increasing the indium composition in the InxGa1−xN well layer or decreasing the TD density of the thick GaN layer, many V defects are generated from the stacking mismatch boundaries induced by stacking faults which are formed within the MQW due to the strain relaxation. Also, TD density in the thick GaN layer affects not only the origin of V-defect formation but also the critical indium composition of the InxGa1−xN well on the formation of V defects. © 2001 American Institute of Physics.
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68.65.Fg Quantum wells
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Nn Stacking faults and other planar or extended defects

Ti/Al/Pt/Au and Al ohmic contacts on Si-substrated GaN

Z. M. Zhao, R. L. Jiang, P. Chen, D. J. Xi, H. Q. Yu, B. Shen, R. Zhang, Y. Shi, S. L. Gu, and Y. D. Zheng

Appl. Phys. Lett. 79, 218 (2001); http://dx.doi.org/10.1063/1.1385189 (3 pages) | Cited 8 times

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Al and Ti/Al/Pt/Au ohmic contacts on GaN epitaxial layers were studied. The epilayers were grown on Si (111) substrates by low-pressure metalorganic chemical vapor deposition. Al/GaN contacts achieved a minimum contact resistivity of 7.5×10−3 Ω cm2 after annealing in N2 ambient at 450 °C for 3 min. Further annealing degraded the contacts. Ti/Al/Pt/Au and GaN contacts achieved a minimum contact resistivity of 8.4×10−5 Ω cm2 after annealing in N2 at 650 °C for 20 s. The Ti/Al/Pt/Au contacts on GaN showed a better thermal stability than Al/GaN contacts. After annealing at 600 °C for 30 min. they were still ohmic contacts. The mechanisms for ohmic contact formation of Ti/Al/Pt/Au contacts were also analyzed. © 2001 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
61.72.Cc Kinetics of defect formation and annealing
73.40.Cg Contact resistance, contact potential

Epitaxy of InAs quantum dots on self-organized two-dimensional InAs islands by atmospheric pressure metalorganic chemical vapor deposition

T. S. Yeoh, C. P. Liu, R. B. Swint, A. E. Huber, S. D. Roh, C. Y. Woo, K. E. Lee, and J. J. Coleman

Appl. Phys. Lett. 79, 221 (2001); http://dx.doi.org/10.1063/1.1379981 (3 pages) | Cited 16 times

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Fully coherent InAs quantum dots and InAs quantum dots grown on self-organized two-dimensional (2D) islands by atmospheric pressure metalorganic chemical vapor deposition are investigated. The significantly lower critical thickness window of between 1 and 2.0 monolayers for fully coherent dots is attributed to the suppression of a segregated indium floating layer. An InAs quantum dot density of 4.7×1010 cm−2 was achieved on GaAs, and a highly localized InAs quantum dot density of over 5×1012 cm−2 was achieved on 2D InAs islands. © 2001 American Institute of Physics.
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81.07.Ta Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
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