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16 Nov 1998

Volume 73, Issue 20, pp. 2857-3009

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Cracking behavior of xerogel silica films on silicon substrates

L. A. Chow, Y. H. Xu, B. Dunn, K. N. Tu, and C. Chiang

Appl. Phys. Lett. 73, 2944 (1998); http://dx.doi.org/10.1063/1.122638 (3 pages) | Cited 10 times

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An analysis of the cracking behavior of sol–gel derived silica, “xerogel,” films on silicon substrates is presented. At the onset of film cracking, xerogel films on 〈100〉 Si substrates show a crosshatched crack pattern, while such films on 〈111〉 Si substrates show a random pattern. This is explained by the fact that for an isotropic film the critical film thickness for cracking decreases for increasing substrate compliance. For a 〈100〉 Si wafer, the directions of highest compliance in the plane of the wafer are in the 〈100〉 directions, which lead to cracks in the film parallel to them. A 〈111〉 Si substrate is isotropic in the plane of the wafer and, hence, there is no preferred direction for film cracking. A random pattern is the result. © 1998 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
62.20.M- Structural failure of materials
81.05.Rm Porous materials; granular materials
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.

Lateral etching and filling of high aspect ratio nanometer-size cavities for silicon device structures

C. A. King, Y. O. Kim, and K. K. Ng

Appl. Phys. Lett. 73, 2947 (1998); http://dx.doi.org/10.1063/1.122639 (3 pages) | Cited 2 times

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We study a process technique involving SiO2 lateral etching coupled with amorphous Si (α-Si) refilling as a possible alternative to improve performance and lower costs for bipolar complementary metal–oxide semiconductor technologies. We investigated the lateral etching of oxide layers with thicknesses between 50 and 2.5 nm confined between a Si substrate and a multilayer stack composed of polycrystalline Si, WSix, and Si3N4. We found that the lateral etching of SiO2 proceeds even with the smallest thickness (2.5 nm) to create extremely small cavities. The etch extent (fixed time) dependence with SiO2 thickness suggests that capillary action may be an important mechanism. Using standard amorphous Si deposition techniques, we refilled all the small cavities without void formation as witnessed from transmission electron micrographs.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
81.65.Cf Surface cleaning, etching, patterning
85.40.Hp Lithography, masks and pattern transfer

Carrier pocket engineering to design superior thermoelectric materials using GaAs/AlAs superlattices

T. Koga, X. Sun, S. B. Cronin, and M. S. Dresselhaus

Appl. Phys. Lett. 73, 2950 (1998); http://dx.doi.org/10.1063/1.122640 (3 pages) | Cited 39 times

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A large enhancement in the thermoelectric figure of merit for the whole superlattice, Z3DT, is predicted for short-period GaAs/AlAs superlattices relative to bulk GaAs. Various superlattice parameters (superlattice growth direction, superlattice period, and layer thicknesses) are explored to optimize Z3DT, including quantum well states formed from carrier pockets at various high symmetry points in the Brillouin zone. The highest room-temperature Z3DT obtained in the present calculation is 0.41 at the optimum carrier concentration for either (001)- or (111)-oriented GaAs (20 Å)/AlAs (20 Å) superlattices, which is about 50 times greater than the corresponding ZT for bulk GaAs. © 1998 American Institute of Physics.
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73.50.Lw Thermoelectric effects
73.61.Ey III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Low resistance Pd/Au ohmic contacts to p-type GaN using surface treatment

Jong Kyu Kim, Jong-Lam Lee, Jae Won Lee, Hyun Eoi Shin, Yong Jo Park, and Taeil Kim

Appl. Phys. Lett. 73, 2953 (1998); http://dx.doi.org/10.1063/1.122641 (3 pages) | Cited 111 times

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Ohmic contact to p-type GaN with the lowest contact resistivity was developed by the surface treatment prior to Pd/Au metal deposition. The contact resistivity drastically decreased from 2.9×10−2 to 4.3×10−4 Ω cm2 by the surface treatment using aqua regia. The surface treatment plays a role in removing the surface oxide formed on p-type GaN during epitaxial growth, and subsequently in reducing the barrier height for holes at the interface of Pd/p-type GaN, resulting in the good ohmic contacts to p-type GaN. © 1998 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
81.05.Ea III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning
73.61.Ey III-V semiconductors

Nonconservative Ostwald ripening of dislocation loops in silicon

Y. L. Huang, M. Seibt, and B. Plikat

Appl. Phys. Lett. 73, 2956 (1998); http://dx.doi.org/10.1063/1.122642 (3 pages) | Cited 3 times

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We have investigated the effects of the proximity of the surface on the ripening behavior of dislocation loops in preamorphized silicon. Starting from well-defined initial conditions, we have varied the location depth of the loops by successive chemical removal of surface layers and measured changes of the size–distribution function during subsequent annealing by means of transmission electron microscopy. Our results show that the amount of Si atoms bound in the loops is not conserved during annealing and that the loop location depth has a prominent effect on the ripening kinetics. Both these observations prove the nonconservative nature of Ostwald ripening of dislocation loops near wafer surfaces. In addition, we observed different ripening kinetics for annealing in vacuum and in Ar which show that different boundary conditions at the surface are established during annealing in these two ambients. © 1998 American Institute of Physics.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Cc Kinetics of defect formation and annealing
61.72.uf Ge and Si
61.82.Fk Semiconductors
61.80.Jh Ion radiation effects

Selective carrier injection into V-groove quantum wires

H. Weman, E. Martinet, A. Rudra, and E. Kapon

Appl. Phys. Lett. 73, 2959 (1998); http://dx.doi.org/10.1063/1.122643 (3 pages) | Cited 14 times

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We have observed selective carrier injection into GaAs/AlGaAs V-groove quantum wires (QWRs) via self-ordered vertical quantum wells (VQWs). Room-temperature I–V characteristics of QWR diodes show a turn-on voltage lower by 0.2 V as compared with planar QW diodes, consistent with the band-gap reduction of 0.2 eV at the vertical QW. This selective injection results in narrow linewidth electroluminescence (∼5 nm at 300 K) emanating exclusively from the QWR from 10 K up to 300 K. © 1998 American Institute of Physics.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.60.Fi Electroluminescence
78.55.Cr III-V semiconductors

Mechanism of photoluminescence of Si nanocrystals fabricated in a SiO2 matrix

K. S. Zhuravlev, A. M. Gilinsky, and A. Yu. Kobitsky

Appl. Phys. Lett. 73, 2962 (1998); http://dx.doi.org/10.1063/1.122644 (3 pages) | Cited 23 times

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The luminescence properties of silicon nanocrystals fabricated by Si ion implantation into a SiO2 matrix and subsequent thermal annealing have been studied. To identify the mechanism of photoluminescence of Si nanocrystals, the dependencies of the steady-state photoluminescence on temperature and excitation power density, and the time-resolved photoluminescence have been investigated. The experimental results point to the mechanism of recombination via the levels of centers which are presumably localized at the silicon nanocrystal–silicon dioxide boundary. © 1998 American Institute of Physics.  
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78.55.Ap Elemental semiconductors
78.47.-p Spectroscopy of solid state dynamics
73.20.At Surface states, band structure, electron density of states
81.07.-b Nanoscale materials and structures: fabrication and characterization

Solid-immersion photoluminescence microscopy of carrier diffusion and drift in facet-growth GaAs quantum wells

Masahiro Yoshita, Motoyoshi Baba, Shyun Koshiba, Hiroyuki Sakaki, and Hidefumi Akiyama

Appl. Phys. Lett. 73, 2965 (1998); http://dx.doi.org/10.1063/1.122645 (3 pages) | Cited 15 times

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Carrier diffusion and drift in facet-growth quantum wells (QWs) on mesa-patterned substrates by molecular beam epitaxy was studied by high-resolution microscopic photoluminescence spectroscopy and imaging using a solid immersion lens at low temperatures. Under point excitation, excitation-position-dependent anisotropic carrier migration was observed, which was explained by carrier diffusion and drift due to spatial change in the quantization energy in QWs. © 1998 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
73.61.Ey III-V semiconductors
81.05.Ea III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
07.60.Pb Conventional optical microscopes

Photoluminescence of GaN: Effect of electron irradiation

I. A. Buyanova, Mt. Wagner, W. M. Chen, B. Monemar, J. L. Lindström, H. Amano, and I. Akasaki

Appl. Phys. Lett. 73, 2968 (1998); http://dx.doi.org/10.1063/1.122646 (3 pages) | Cited 27 times

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The effect of electron irradiation on the optical properties of GaN material with various electrical conductivity (i.e., n type, compensated, and p type) is studied in detail by photoluminescence (PL) spectroscopy. Electron irradiation with a dose <1017 cm−2 is found to have a minor effect on photoluminescence, indicating a high radiation resistance of GaN. For higher doses, two major effects of electron irradiation on PL properties can be distinguished, i.e., radiation-induced quenching of the PL, likely caused by a radiation-induced formation of competing recombination channels, and radiation-induced formation/activation of new optically active centers. © 1998 American Institute of Physics.
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78.55.Cr III-V semiconductors
61.82.Fk Semiconductors
61.80.Fe Electron and positron radiation effects
78.66.Fd III-V semiconductors

An equation for thermionic currents in vacuum energy conversion diodes

Albert C. Marshall

Appl. Phys. Lett. 73, 2971 (1998); http://dx.doi.org/10.1063/1.122647 (3 pages) | Cited 2 times

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Apparent thermionic emission constants A∗ are commonly reported with values deviating from the theoretical value of 120 A/cm2 K2. For thermionic energy conversion diodes, using A∗ in the conventional equation for predicting net currents is found to violate basic physics laws and may result in poor predictive accuracy. A general equation for vacuum energy conversion diodes is proposed to prevent misuse of A∗. © 1998 American Institute of Physics.
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84.60.Ny Thermionic conversion
84.47.+w Vacuum tubes

Nanoscale surface clustering on CdTe epilayers

L. Marsal, H. Mariette, Y. Samson, J. L. Rouvière, and E. Picard

Appl. Phys. Lett. 73, 2974 (1998); http://dx.doi.org/10.1063/1.122648 (3 pages) | Cited 14 times

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We have studied the surface morphology of two dimensional CdTe films grown by atomic layer epitaxy on CdZnTe buffers. Atomic force microscopy observations in air show a strong evolution of the surface after the growth by forming clusters of around 20 nm in diameter and 3 nm in height. The size increase of these clusters as time proceeds is directly related to the formation of tellurium and cadmium oxides on the surface as revealed by x-ray photoelectron spectroscopy data. This nanoscale clustering then occurs ex situ, due to exposure to atmosphere which induces an oxidation of the CdTe epilayers. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.05.Dz II-VI semiconductors
81.65.Mq Oxidation
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Neutralized (NH4)2S solution passivation of III–V phosphide surfaces

Z. L. Yuan, X. M. Ding, B. Lai, X. Y. Hou, E. D. Lu, P. S. Xu, and X. Y. Zhang

Appl. Phys. Lett. 73, 2977 (1998); http://dx.doi.org/10.1063/1.122649 (3 pages) | Cited 12 times

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Synchrotron radiation photoelectron spectroscopy has been used to investigate III–V phosphide GaP and InP (100) surfaces treated with a neutralized (NH4)2S solution. Compared to the conventional basic (NH4)2S solution treatment, a thick sulfide layer with P–S bond and strong Ga–S (In–S) bond of high thermal stability is formed on the neutralized (NH4)2S-treated GaP (InP) (100) surfaces. The possible passivation mechanisms of the two (NH4)2S solutions to III–V phosphide surfaces are also discussed. © 1998 American Institute of Physics.
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81.65.Rv Passivation
81.05.Ea III-V semiconductors
79.60.Bm Clean metal, semiconductor, and insulator surfaces
73.20.-r Electron states at surfaces and interfaces

Depth profiling of vacancy clusters in MeV-implanted Si using Au labeling

V. C. Venezia, D. J. Eaglesham, T. E. Haynes, Aditya Agarwal, D. C. Jacobson, H.-J. Gossmann, and F. H. Baumann

Appl. Phys. Lett. 73, 2980 (1998); http://dx.doi.org/10.1063/1.122650 (3 pages) | Cited 51 times

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A technique for profiling the clustered-vacancy region produced by high-energy ion implantation into silicon is described and tested. This technique takes advantage of the fact that metal impurities, such as Au, are trapped in the region of excess vacancies produced by MeV Si implants into silicon. In this work, the clustered-vacancy regions produced by 1-, 2-, and 8-MeV Si implants into silicon have been labeled with Au diffused in from the front surface at 750 °C. The trapped Au was profiled with Rutherford backscattering spectrometry. The dynamics of the clustered-vacancy region were monitored for isochronal annealing at 750–1000 °C, and for isothermal annealing at 950 °C, for 10–600 s. Cross-sectional transmission electron microscopy analysis revealed that after the drive-in anneal, the Au in the region of vacancy clusters is in the form of precipitates. The results demonstrate that the Au-labeling technique offers a convenient and potentially quantitative tool for depth profiling vacancies in clusters. © 1998 American Institute of Physics.
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61.72.Yx Interaction between different crystal defects; gettering effect
61.72.uf Ge and Si
61.72.J- Point defects and defect clusters
61.82.Fk Semiconductors
61.80.Jh Ion radiation effects
61.72.Cc Kinetics of defect formation and annealing
64.75.-g Phase equilibria
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis

Ultrafast detection and autocorrelation of picosecond THz radiation pulses with a GaAs/AlAs superlattice

S. Winnerl, W. Seiwerth, E. Schomburg, J. Grenzer, K. F. Renk, C. J. G. M. Langerak, A. F. G. van der Meer, D. G. Pavel’ev, Yu. Koschurinov, A. A. Ignatov, B. Melzer, V. Ustinov, S. Ivanov, and P. S. Kop’ev

Appl. Phys. Lett. 73, 2983 (1998); http://dx.doi.org/10.1063/1.122651 (3 pages) | Cited 14 times

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We used a wide miniband GaAs/AlAs superlattice (at room temperature) for detection and autocorrelation of picosecond THz radiation pulses (frequency 4.3 THz) from a free-electron laser. The detection was based on a THz-field induced change in conductivity of the superlattice, and the correlation on the nonlinearity of the conductivity change at strong THz-pulse-power. The nonlinear conductivity change was due to two effects, which we attribute to dynamical localization of miniband electrons and to ionization of deep impurity centers. © 1998 American Institute of Physics.
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73.50.Fq High-field and nonlinear effects
73.61.Ey III-V semiconductors
71.55.Eq III-V semiconductors
85.60.Gz Photodetectors (including infrared and CCD detectors)

Indium transient enhanced diffusion

P. B. Griffin, M. Cao, P. Vande Voorde, Y.-L. Chang, and W. M. Greene

Appl. Phys. Lett. 73, 2986 (1998); http://dx.doi.org/10.1063/1.122652 (3 pages) | Cited 22 times

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Indium, an acceptor dopant in silicon, is a large atom with a low diffusion coefficient potentially suitable for doping the channel of transistors. Systematic experiments are described which measure the susceptibility of indium to transient enhanced diffusion caused by ion implant damage introduced during the transistor fabrication process. We find that indium diffusion is dramatically enhanced by a source of interstitials and that the amount of enhancement is comparable to that seen for boron. Indium is preferable as a channel dopant not because of its diffusion behavior, but rather because a narrow ion implanted distribution can be obtained using the heavy indium ion, giving a more steeply retrograde profile than can be achieved by boron doping. These results help clarify the physics of indium and boron doping in small devices. © 1998 American Institute of Physics.
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66.30.J- Diffusion of impurities
61.72.uf Ge and Si
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
85.40.Ry Impurity doping, diffusion and ion implantation technology
72.80.Cw Elemental semiconductors
81.05.Cy Elemental semiconductors
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