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12 Nov 2001

Volume 79, Issue 20, pp. 3215-3366

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Stress control in GaN grown on silicon (111) by metalorganic vapor phase epitaxy

Eric Feltin, B. Beaumont, M. Laügt, P. de Mierry, P. Vennéguès, H. Lahrèche, M. Leroux, and P. Gibart

Appl. Phys. Lett. 79, 3230 (2001); http://dx.doi.org/10.1063/1.1415043 (3 pages) | Cited 70 times

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The strain in GaN epitaxial layers grown on silicon (111) substrates by metalorganic vapor phase epitaxy has been investigated. The insertion of AlN/GaN superlattices was found to decrease the stress sufficiently for avoiding crack formation in an overgrown thick (2.5 μm) GaN layer. X-ray diffraction and photoluminescence measurements are used to determine the effect of these AlN/GaN superlattices on the strain in the subsequent GaN layers. A reduction of threading dislocation density is also observed by transmission electron microscopy and atomic force microscopy when such superlattices are used. Strong band edge photoluminescence of GaN on Si(111) was observed with a full width at half maximum of the bound exciton line as low as 6 meV at 10 K. The 500 arcsec linewidth on the (002) x-ray rocking curve also attests the high crystalline quality of GaN on Si (111), when using these AlN/GaN superlattices. © 2001 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.55.Cr III-V semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Lk Linear defects: dislocations, disclinations
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Aluminum-induced crystallization of hydrogenated amorphous germanium thin films

I. Chambouleyron, F. Fajardo, and A. R. Zanatta

Appl. Phys. Lett. 79, 3233 (2001); http://dx.doi.org/10.1063/1.1415772 (3 pages) | Cited 16 times

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Al-induced crystallization of co sputtered hydrogenated amorphous germanium films, deposited at 220 °C, onto crystalline silicon substrates is investigated by Raman and infrared spectroscopies as a function of the Al concentration (2×10−6<[Al/Ge]<2.5×10−2). Aluminum induces partial crystallization of the films for metal concentrations smaller than ∼1.3 at. %. A sort of explosive crystallization of the films occurs within a narrow Al concentration range ( ∼ 1.3<[Al/Ge]< ∼ 1.8 at. %). Raman spectra do not display any crystallization signal for metal concentrations above this narrow range. Data of the extended x-ray absorption fine structure of the coordination and of the local order around gallium, in Ga-doped a-Ge:H, are used to propose an overall picture of the microscopic mechanisms behind these results. A comparative analysis suggests that the crystallization seeds are fourfold-coordinated Al atoms sitting at the center of perfect tetrahedral Ge sites. © 2001 American Institute of Physics.
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78.66.Jg Amorphous semiconductors; glasses
78.66.Db Elemental semiconductors and insulators
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.30.Am Elemental semiconductors and insulators
78.70.Dm X-ray absorption spectra

Electromigration critical length effect in Cu/oxide dual-damascene interconnects

Ki-Don Lee, Ennis T. Ogawa, Hideki Matsuhashi, Patrick R. Justison, Kil-Soo Ko, Paul S. Ho, and Volker A. Blaschke

Appl. Phys. Lett. 79, 3236 (2001); http://dx.doi.org/10.1063/1.1418034 (3 pages) | Cited 27 times

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Electromigration tests at temperatures between 340 and 400 °C and current densities between 1.0 and 3.0 MA/cm2 have been performed to determine the temperature dependence of the critical length effect in 0.5-μm-wide Cu/oxide dual-damascene interconnects with 0.1 μm silicon nitride (SiNx) passivation. A focused-ion-beam-induced contrast imaging technique is used to locate failure sites of critical length test structures. Statistical analysis [E. T. Ogawa et al., Appl. Phys. Lett. 78, 18 (2001)] yields a threshold-length product (jL)c, of 3700 A/cm, and a temperature dependence is not observed within the temperature range 340–400 °C. © 2001 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Qa Electromigration

The nature of arsenic incorporation in GaN

A. Bell, F. A. Ponce, S. V. Novikov, C. T. Foxon, and I. Harrison

Appl. Phys. Lett. 79, 3239 (2001); http://dx.doi.org/10.1063/1.1418030 (3 pages) | Cited 3 times

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A systematic study of the nature of arsenic incorporation in GaN grown by molecular-beam epitaxy is presented. The samples were grown with concentrations of arsenic ranging from 3.4×1017 to 4.2×1018 cm−3. Secondary ion mass spectroscopy data show that increasing the As concentration has the effect of increasing the amount of As in the nitrogen site as compared to As in the gallium site. This trend is used to explain the reduction in carrier mobility with increasing As concentration. © 2001 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
81.05.Ea III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.S- Impurities in crystals
73.61.Ey III-V semiconductors
85.40.Ry Impurity doping, diffusion and ion implantation technology
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
73.50.Dn Low-field transport and mobility; piezoresistance

Atomistic evolution of Si1–x–yGexCy thin films on Si(001) surfaces

Akira Sakai, Yuji Torige, Masahisa Okada, Hiroya Ikeda, Yukio Yasuda, and Shigeaki Zaima

Appl. Phys. Lett. 79, 3242 (2001); http://dx.doi.org/10.1063/1.1418447 (3 pages) | Cited 6 times

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The initial growth process of Si1−x−yGexCy thin films on Si(001) surfaces is examined by scanning tunneling microscopy. The surface morphology of the film critically depends on the C fraction in the film. Evidence is presented on an atomic scale that the epitaxial growth of Si1−x−yGexCy films with large C fractions is dominated by phase separation between Si–C and Si–Ge, concomitant with C condensation on the surface of the growing films. We find that the addition of a thin (1–2 ML) SiGe interlayer between the Si1−x−yGexCy film and the Si substrate drastically improves the film structure, leading to a planar morphology even with large C fractions present in the film. © 2001 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
64.75.-g Phase equilibria
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.35.B- Structure of clean surfaces (and surface reconstruction)

Optical and electrical properties of Al-rich AlGaN alloys

J. Li, K. B. Nam, J. Y. Lin, and H. X. Jiang

Appl. Phys. Lett. 79, 3245 (2001); http://dx.doi.org/10.1063/1.1418255 (3 pages) | Cited 48 times

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AlxGa1−xN alloys with x up to 0.7 were grown by metalorganic chemical vapor deposition and their optical properties were investigated by deep UV time-resolved photoluminescence (PL) spectroscopy. Our results revealed that both the activation energy of the PL emission intensity and the PL decay lifetime exhibit sharp increases at x of around 0.4. The results can be understood in terms of the sharp increase of the impurity binding energy or the carrier/exciton localization energy around x = 0.4. A three orders of magnitude increase in resistivity of undoped AlGaN alloys at x of around 0.4 was also observed, which further corroborated the optical results. © 2001 American Institute of Physics.
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78.55.Cr III-V semiconductors
72.80.Ey III-V and II-VI semiconductors
78.47.-p Spectroscopy of solid state dynamics
72.20.Fr Low-field transport and mobility; piezoresistance

Femtosecond laser triggering of a sub-100 picosecond jitter high-voltage spark gap

B. M. Luther, L. Furfaro, A. Klix, and J. J. Rocca

Appl. Phys. Lett. 79, 3248 (2001); http://dx.doi.org/10.1063/1.1419036 (3 pages) | Cited 9 times

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We have demonstrated sub-100 ps jitter operation of a pressurized high-voltage air spark gap triggered by a femtosecond Ti:Sapphire laser. Time delay statistical fluctuations with a standard deviation as low as +−σ = 0.037 ns were obtained. © 2001 American Institute of Physics.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.75.Kq Plasma switches (e.g., spark gaps)
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.62.-b Laser applications

Stable island arrays by height-constrained Stranski–Krastanov growth

J. Liang and Z. Suo

Appl. Phys. Lett. 79, 3251 (2001); http://dx.doi.org/10.1063/1.1415403 (3 pages) | Cited 3 times

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In the Stranski–Krastanov system, the lattice mismatch between the film and the substrate causes the film to break into islands. During annealing, both surface energy, and elastic energy drive the islands to coarsen: some islands enlarge and others shrink, keeping the total island volume constant. The islands produced this way are usually uneven in size and spacing. Motivated by several related studies, we suggest that stable, uniform islands should form when a stiff ceiling is placed at a small gap above the film. After contacting the ceiling, the islands are constrained to grow laterally and remain coherent with the substrate, preventing further stress relaxation. In fact, we show that the role of elasticity is reversed: with the ceiling, the total elastic energy stored in the system increases as the islands coarsen laterally. On the other hand, the total surface energy decreases as the islands coarsen. Consequently, the islands select an equilibrium size to minimize the combined elastic energy and surface energy. We estimate the equilibrium island size by analyzing an idealized model.© 2001 American Institute of Physics.
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68.55.A- Nucleation and growth
68.43.Jk Diffusion of adsorbates, kinetics of coarsening and aggregation
68.35.Md Surface thermodynamics, surface energies
68.60.Bs Mechanical and acoustical properties
68.65.Hb Quantum dots (patterned in quantum wells)
62.20.D- Elasticity

Crystal-polarity dependence of Ti/Al contacts to freestanding n-GaN substrate

Joon Seop Kwak, K. Y. Lee, J. Y. Han, J. Cho, S. Chae, O. H. Nam, and Y. Park

Appl. Phys. Lett. 79, 3254 (2001); http://dx.doi.org/10.1063/1.1419053 (3 pages) | Cited 42 times

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The effect of crystal polarity on the electrical properties of Ti/Al contacts to n-GaN substrate has been investigated. The Ti/Al contacts prepared on Ga-face n-GaN substrate became ohmic with a contact resistivity of 2×10−5 Ω cm2 after annealing at temperatures higher than 600 °C for 30 s. On the contrary, the contacts on N-face n-GaN substrate exhibited nonlinear current–voltage curve and high Schottky barrier heights over 1 eV were measured at the same annealing conditions. These results could be explained by opposite piezoelectric-field at GaN/AlN heterostructure resulted from different polarity of the GaN substrate. © 2001 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
81.05.Ea III-V semiconductors
73.40.Cg Contact resistance, contact potential
61.72.Cc Kinetics of defect formation and annealing
73.30.+y Surface double layers, Schottky barriers, and work functions

Evidence of electron-emission-enhanced nucleation of diamonds in microwave plasma-enhanced chemical vapor deposition

Kuoguang Perng, Kuo-Shung Liu, and I-Nan Lin

Appl. Phys. Lett. 79, 3257 (2001); http://dx.doi.org/10.1063/1.1419233 (3 pages) | Cited 1 time

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The bias-enhanced nucleation (BEN) of diamonds on a Si substrate, using a SiO2 mask and microwave plasma-enhanced chemical vapor deposition (MPE-CVD), was examined. Experimental results indicate that the electron-emission-enhanced nucleation mechanism proposed herein governs the nucleation of diamonds on the partially patterned SiO2/Si substrate. The variation of nucleation density on the partially patterned SiO2/Si substrate also reveals that the BEN of diamonds in the MPE-CVD process follows the proposed mechanism. © 2001 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.U- Carbon/carbon-based materials
81.05.Cy Elemental semiconductors
68.55.A- Nucleation and growth
52.77.Dq Plasma-based ion implantation and deposition
85.40.Hp Lithography, masks and pattern transfer

Use of TiN(O)/Ti as an effective intermediate stress buffer and diffusion barrier for Cu/parylene-n interconnects

Kaustubh S. Gadre, T. L. Alford, and J. W. Mayer

Appl. Phys. Lett. 79, 3260 (2001); http://dx.doi.org/10.1063/1.1416156 (3 pages) | Cited 5 times

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Copper and parylene-n (Pa-n) are studied for ultralarge scale integration circuits because of their low electrical resistivity, resistance to electromigration and low dielectric constant, chemical inertness, and compatibility with current integrated circuit manufacturing, respectively. Copper diffusion observed at and above 300 °C in Pa-n correlates to an increase in the crystallinity of the α phase and subsequent transformation to the more open structure of β parylene. Titanium nitride (oxygen) [TiN(O)]/titanium (Ti) bilayers are successfully implemented as a diffusion barrier. TiN is proven to be a very good diffusion barrier up to 500 °C for copper due to its large negative heat of formation and hence its thermal stability. Incorporation of an intermediate titanium layer reduced the residual stress and thermal mismatch between Pa-n and TiN. Without the Ti layer thermal cracking of TiN occurred. The presence of the buffer layer had no detrimental effects on the overall resistivity. The effectiveness of the barrier is attributed to stuffing of the grain boundaries with oxygen and nitrogen. This results in the elimination of rapid diffusion paths. This work provides the foundation for future implementation of Cu/Pa-n for higher temperature microelectronics. © 2001 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
73.40.Ns Metal-nonmetal contacts
85.40.Ls Metallization, contacts, interconnects; device isolation
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