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5 Apr 1999

Volume 74, Issue 14, pp. 1933-2093

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Nonlinear optical absorption and temporal response of arsenic- and oxygen-implanted GaAs

M. J. Lederer, B. Luther-Davies, H. H. Tan, C. Jagadish, M. Haiml, U. Siegner, and U. Keller

Appl. Phys. Lett. 74, 1993 (1999); http://dx.doi.org/10.1063/1.123724 (3 pages) | Cited 16 times

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We have measured the nonlinear optical absorption of arsenic and oxygen implanted epitaxial GaAs for a range of ion doses and annealing temperatures. The response time, τA, and a parameter, Mmax, which characterizes the performance of the structures as modulators, are both reduced by implantation, and correspondingly the nonbleachable losses are increased. We show that similar combinations of (τA, Mmax) can be achieved using either ion species and various combinations of dose and annealing temperatures. Furthermore, the data were all located on a well-defined curve in the (τA, Mmax) plane, provided amorphization, which occurs at high implant doses, was avoided. We deduce that there exists a limit to the modulation if a specific response time is required. © 1999 American Institute of Physics.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
78.66.Fd III-V semiconductors
42.70.Mp Nonlinear optical crystals
78.47.-p Spectroscopy of solid state dynamics
81.40.Gh Other heat and thermomechanical treatments
81.40.Tv Optical and dielectric properties related to treatment conditions
61.72.uj III-V and II-VI semiconductors

Application of a new airbridge-gate structure for high-performance Ga0.51In0.49P/In0.15Ga0.85As/GaAs pseudomorphic field-effect transistors

Wen-Chau Liu, Wen-Lung Chang, Hsi-Jen Pan, Kuo-Hui Yu, Shung-Ching Feng, and Wen-Shiung Lour

Appl. Phys. Lett. 74, 1996 (1999); http://dx.doi.org/10.1063/1.123725 (3 pages) | Cited 3 times

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A new high-performance Ga0.51In0.49P/In0.15Ga0.85As/GaAs pseudomorphic heterostructure field-effect transistor, based on a novel airbridge-gate structure with multiple piers, has been fabricated successfully. Due to the employment of high Schottky barrier GaInP layer and the newly designed double delta-doped sheets (D3S) InGaAs channel, the high gate-to-drain breakdown voltage and broad and linear transconductance are obtained simultaneously. Moreover, the use of airbridge-gate technique not only suppresses the parasitic capacitance, but also exhibits a wide and flat operation regime of the current gain cutoff frequency fT and maximum oscillation frequency fmax. © 1999 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.Tv Field effect devices
73.30.+y Surface double layers, Schottky barriers, and work functions
73.61.Ey III-V semiconductors

DX centers in GaAs/Si-δ/AlAs heterostructure

R. H. Miwa and T. M. Schmidt

Appl. Phys. Lett. 74, 1999 (1999); http://dx.doi.org/10.1063/1.123726 (3 pages) | Cited 8 times

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Microscopic mechanisms of impurity spreading in GaAs/Si-δ/AlAs heterostructure have been investigated using an ab initio pseudopotential total energy calculation. Our results showed that silicon atoms can move from the δ-doped plane occupying interstitial positions, favored by the high doped concentration, forming DX centers. The silicon impurity position, out of the δ plane in the AlAs layers, presents an energetically stable configuration, and in the GaAs layers, presents a metastable configuration. As a consequence a silicon doping limit is reached due to the presence of localized deep states inside the band gap, when silicon atoms are in interstitial positions. © 1999 American Institute of Physics.
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73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
71.15.Nc Total energy and cohesive energy calculations
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
73.61.Ey III-V semiconductors
61.72.J- Point defects and defect clusters

Free-carrier screening of polarization fields in wurtzite GaN/InGaN laser structures

Fabio Della Sala, Aldo Di Carlo, Paolo Lugli, Fabio Bernardini, Vincenzo Fiorentini, Reinhard Scholz, and Jean-Marc Jancu

Appl. Phys. Lett. 74, 2002 (1999); http://dx.doi.org/10.1063/1.123727 (3 pages) | Cited 129 times

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The free-carrier screening of macroscopic polarization fields in wurtzite GaN/InGaN quantum well lasers is investigated via a self-consistent tight-binding approach. We show that the high carrier concentrations found experimentally in nitride laser structures effectively screen the built-in spontaneous and piezoelectric polarization fields, thus inducing a “field-free” band profile. Our results explain some heretofore puzzling experimental data on nitride lasers, such as the unusually high lasing excitation thresholds and emission blue shifts for increasing excitation levels. © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.66.Fd III-V semiconductors
73.61.Ey III-V semiconductors
73.20.At Surface states, band structure, electron density of states
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
31.15.xr Self-consistent-field methods

Bonding constraints and defect formation at interfaces between crystalline silicon and advanced single layer and composite gate dielectrics

G. Lucovsky, Y. Wu, H. Niimi, V. Misra, and J. C. Phillips

Appl. Phys. Lett. 74, 2005 (1999); http://dx.doi.org/10.1063/1.123728 (3 pages) | Cited 76 times

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An increasingly important issue in semiconductor device physics is understanding of how departures from ideal bonding at silicon–dielectric interfaces generate electrically active defects that limit performance and reliability. Building on previously established criteria for formation of low defect density glasses, constraint theory is extended to crystalline silicon–dielectric interfaces that go beyond Si–SiO2 through development of a model that quantifies average bonding coordination at these interfaces. This extension is validated by application to interfaces between Si and stacked silicon oxide/nitride dielectrics demonstrating that as in bulk glasses and thin films, an average coordination, Nav, greater than three yields increasing defective interfaces. © 1999 American Institute of Physics.
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68.35.Ct Interface structure and roughness
85.30.De Semiconductor-device characterization, design, and modeling
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.20.Hb Impurity and defect levels; energy states of adsorbed species
61.50.Lt Crystal binding; cohesive energy
61.72.-y Defects and impurities in crystals; microstructure

Ultraviolet Raman stress mapping in silicon

M. Holtz, J. C. Carty, and W. M. Duncan

Appl. Phys. Lett. 74, 2008 (1999); http://dx.doi.org/10.1063/1.123729 (3 pages) | Cited 14 times

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We report micro-Raman stress imaging in silicon structures using 351 nm excitation. This excitation has an extremely shallow optical penetration depth ( ≈ 5 nm) in silicon. It should also ultimately provide higher spatial resolution compared to visible wavelengths used in micro-Raman studies. As a test we examine a wafer which consists of a patterned nitride/polycrystalline silicon/oxide/substrate “stack” with neighboring regions of device-quality silicon covered only by a thin oxide layer. We obtain two-dimensional images with spatial resolutions ranging from 1 to 4 μm. The smallest Raman shift reliably detectable is found to be ±0.07 cm−1, corresponding to a stress magnitude of 35 MPa. Stresses on the order of 140 MPa are observed beneath the stack region. The contrasting linewidths between the substrate and polycrystalline silicon provide a complementary image. © 1999 American Institute of Physics.
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81.05.Cy Elemental semiconductors
78.30.Am Elemental semiconductors and insulators
78.40.Fy Semiconductors
81.70.Fy Nondestructive testing: optical methods

Characterization of carrier-trapping phenomena in ultrathin chemical oxides using x-ray photoelectron spectroscopy time-dependent measurements

Y. Hagimoto, T. Fujita, K. Ono, H. Fujioka, M. Oshima, K. Hirose, and M. Tajima

Appl. Phys. Lett. 74, 2011 (1999); http://dx.doi.org/10.1063/1.123730 (3 pages) | Cited 5 times

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We report a technique to characterize carrier-trapping phenomena in SiO2 by measuring the Si 2p core-level energy of Si substrates covered with thin SiO2 layers as a function of x-ray irradiation time. It is found that the Si 2p peak energy, which corresponds to the band bending at the SiO2/Si interface, changes as the x-ray irradiation time increases. We attribute this to carrier-trapping phenomena in SiO2. By using this technique, it is found that the carrier-trapping phenomena differ remarkably among several chemical oxides. We also discuss the atomic structure of the traps that cause the trapping phenomena. © 1999 American Institute of Physics.
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79.60.Jv Interfaces; heterostructures; nanostructures
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Three color coherent generation and control of current in low-temperature-grown GaAs

J. M. Fraser, A. Haché, A. I. Shkrebtii, J. E. Sipe, and H. M. van Driel

Appl. Phys. Lett. 74, 2014 (1999); http://dx.doi.org/10.1063/1.123731 (3 pages) | Cited 8 times

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We demonstrate coherent generation and control of electrical currents in low-temperature-grown GaAs at 300 K using three phase-related, 150 fs pulses derived from a parametric process. Interference between single photon (0.8 μm) and nondegenerate two photon (1.4 and 1.8 μm) absorption amplitudes generates ballistic electrical currents whose beam polarization dependence is in agreement with a simple Fermi’s golden rule calculation. © 1999 American Institute of Physics.
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72.40.+w Photoconduction and photovoltaic effects
42.65.Yj Optical parametric oscillators and amplifiers
73.23.-b Electronic transport in mesoscopic systems

Modeling of the effects of dose, dose rate, and implant temperature on transient enhanced diffusion

Lourdes Pelaz, G. H. Gilmer, V. C. Venezia, H.-J. Gossmann, M. Jaraiz, and J. Barbolla

Appl. Phys. Lett. 74, 2017 (1999); http://dx.doi.org/10.1063/1.123742 (3 pages) | Cited 25 times

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Atomistic simulations are used to study the effects of implant parameters on transient enhanced diffusion (TED). We analyze 10 keV Si implants in a wide range of doses from 108 to 1014 ions/cm2, dose rates from 1010 to 1014 ions/cm2 s, and implant temperature from room temperature to 1000 °C. Different regimes with different dependence of TED on these parameters are observed. For high doses, high dose rates, and low implant temperatures, the Frenkel pairs are accumulated during ion implantation, and the resulting damage is very dense. During the postimplant annealing, the recombination of Frenkel pairs is efficient, and the extra interstitials generated by the implanted ions provide the main contribution to the enhanced diffusivity. For low doses, low dose rates, and high implant temperatures, there is little interaction between neighboring cascades during annealing. The recombination of Frenkel pairs is not complete, and many interstitials and vacancies from each cascade survive recombination and contribute significantly to TED. © 1999 American Institute of Physics.
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66.30.H- Self-diffusion and ionic conduction in nonmetals
66.30.Dn Theory of diffusion and ionic conduction in solids
61.72.uf Ge and Si
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments

Direct observation of strained substrate in graded Si1−xGex/Si heterostructures

M. Tao and J. W. Lyding

Appl. Phys. Lett. 74, 2020 (1999); http://dx.doi.org/10.1063/1.123743 (3 pages) | Cited 1 time

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Cross-sectional scanning tunneling microscopy is used to study strain relaxation in a graded Si1−xGex/Si heterostructure. Two strain relaxation mechanisms are observed on the (111) cleaved surface. One is through stressing the substrate, and the strained region in the substrate can extend several hundred Angstroms from the interface. The other strain relaxation mechanism is through defect formation, i.e., atomic steps, on the cleaved surface. This is analogous to misfit dislocations in bulk strain relaxation. Interaction between these two strain relaxation mechanisms is also observed, with the presence of atomic steps reducing the strained region in the substrate. © 1999 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.35.Ct Interface structure and roughness

Aluminum gallium nitride short-period superlattices doped with magnesium

A. Saxler, W. C. Mitchel, P. Kung, and M. Razeghi

Appl. Phys. Lett. 74, 2023 (1999); http://dx.doi.org/10.1063/1.123744 (3 pages) | Cited 19 times

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Short-period superlattices consisting of alternating layers of GaN:Mg and AlGaN:Mg were grown by low-pressure organometallic vapor phase epitaxy. The electrical properties of these superlattices were measured as a function of temperature and compared to conventional AlGaN:Mg layers. It is shown that the optical absorption edge can be shifted to shorter wavelengths while lowering the acceptor ionization energy by using short-period superlattice structures instead of bulk-like AlGaN:Mg. © 1999 American Institute of Physics.
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73.61.Ey III-V semiconductors
78.40.Fy Semiconductors
78.66.Fd III-V semiconductors
73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Light-induced mobility enhancement in delta-doped GaAs/In0.26Ga0.74As/GaAs quantum wells grown by molecular beam epitaxy on GaAs(001)

M. Zervos, M. Elliott, and D. I. Westwood

Appl. Phys. Lett. 74, 2026 (1999); http://dx.doi.org/10.1063/1.123745 (3 pages) | Cited 10 times

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We have studied persistent photoconductivity in 80 Å strained GaAs/In0.26Ga0.74As/GaAs quantum wells grown by molecular beam epitaxy at 480 °C by measuring the Shubnikov de Haas and Hall effects at 4.2 K. Each quantum well was δ doped with Si to 2×1012 cm−2 either (i) at the center of the quantum well, (ii) at the lower interface, or (iii) the bottom barrier. The free-carrier density after exposure to 654 nm red light with above-band-gap energy did not exceed significantly the intended δ-doping level, but the Hall mobility increased dramatically and was accompanied by stronger Shubnikov de Haas oscillations. We attribute this to electron–hole pair generation and separation and/or the photoionization of deep states, which create a positive space charge in the surface depletion region. This leads to electrostatic bandbending, which converts the quantum well from being asymmetric in the dark to square-like after illumination and shifts the charge distribution away from the δ layer, improving the mobility. This hypothesis is corroborated by the light insensitivity of both an identical heterostructure δ doped to 2×1012 cm−2 in the top barrier and an equivalent set of heterostructures δ doped with Si to 4.5×1012 cm−2. © 1999 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.50.Pz Photoconduction and photovoltaic effects
72.20.My Galvanomagnetic and other magnetotransport effects
73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Effects of As/P exchange reaction on the formation of InAs/InP quantum dots

Sukho Yoon, Youngboo Moon, Tae-Wan Lee, Euijoon Yoon, and Young Dong Kim

Appl. Phys. Lett. 74, 2029 (1999); http://dx.doi.org/10.1063/1.123746 (3 pages) | Cited 54 times

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InAs self-assembled quantum dots (SAQDs) were grown on InP at various temperatures and V/III ratios by metalorganic chemical vapor deposition. The density, size distribution, and shape of the InAs SAQDs changed significantly with temperature and V/III ratio. Careful analysis of the total volume of the dots grown at various conditions showed that the volume far exceeded the amount of deposition supplied from the gas-phase sources. The amount of excess InAs and the aspect ratio (height/lateral size) of the SAQD increased with temperature and V/III ratio, strongly suggesting that the As/P exchange reaction at the surface played an important role in the kinetics of SAQD formation. Insertion of a lattice-matched InGaAs buffer layer suppressed the excess InAs formation, and lowered the aspect ratio, confirming the effect of the As/P exchange reaction. © 1999 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Characterization of electronic states in molecular beam epitaxy grown GaN by optical admittance spectroscopy: Comparison of different nitrogen plasma sources

A. Krtschil, H. Witte, M. Lisker, J. Christen, U. Birkle, S. Einfeldt, and D. Hommel

Appl. Phys. Lett. 74, 2032 (1999); http://dx.doi.org/10.1063/1.123747 (3 pages) | Cited 2 times

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Optical transitions between the bands and electronic states in n-type GaN layers grown by molecular beam epitaxy on sapphire substrates using an electron cyclotron resonance (ECR) or a radio frequency (rf) nitrogen plasma source were investigated by means of optical admittance spectroscopy. The spectra of all layers similarly consist of a band gap region, a blue and a yellow band, and several defect-to-band transitions. However, in rf grown layers distinct transitions are separable, whereas ECR grown samples reveal broad bands, originating from potential fluctuations due to structural inhomogeneities induced by the ECR source. A defect at 0.82 eV is found characteristic for all ECR samples. © 1999 American Institute of Physics.
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71.55.Gs II-VI semiconductors
73.61.Ga II-VI semiconductors
78.66.Hf II-VI semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Cathodoluminescence mapping of epitaxial lateral overgrowth in gallium nitride

S. J. Rosner, G. Girolami, H. Marchand, P. T. Fini, J. P. Ibbetson, L. Zhao, S. Keller, U. K. Mishra, S. P. DenBaars, and J. S. Speck

Appl. Phys. Lett. 74, 2035 (1999); http://dx.doi.org/10.1063/1.123748 (3 pages) | Cited 36 times

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The dislocation arrangements in gallium nitride (GaN) films prepared by lateral epitaxial overgrowth (LEO) have been studied by cathodoluminescence mapping and transmission electron microscopy. A very low density of electrically active defects (<10−6 cm−2) in the laterally overgrown material is observed. Individual electrically active defects have been observed that propagate laterally from the line of stripe coalescence into the overgrown material. Additionally, by mapping wavelength-resolved luminescence in an InGaN quantum well grown on top of the overgrown material, these defects are shown to be limited to the underlying material and do not propagate normal to the surface, as in other GaN films. In the seed region, threading dislocation image widths are seen to be nearly identical in the quantum well and the underlying GaN, indicating a comparable upper limit (∼200 nm) for minority carrier diffusion length in InGaN and GaN. Additionally, it is shown that, through processing variation, these lateral defects can be avoided in LEO films and that wavelength-resolved cathodoluminescence is an excellent large-area method for rapidly and quantitatively observing variations in process development. © 1999 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
78.66.Fd III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.61.Ey III-V semiconductors

Evolution of {311} type defects in boron-doped structures: Experimental evidence of boron–interstitial cluster formation

A. D. Lilak, S. K. Earles, M. E. Law, and K. S. Jones

Appl. Phys. Lett. 74, 2038 (1999); http://dx.doi.org/10.1063/1.123749 (3 pages) | Cited 12 times

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Boron-doped well structures formed in Czochralski silicon are subjected to a self-implant and various anneals to form a population of type {311} defects. Quantitative transmission electron microscopy is then used to measure the residual interstitials trapped in the {311} defects as a function of boron concentration and anneal temperature. We have found a strong tendency for increased dissolution rates of {311} type defects at boron concentrations above 1018 cm−3, providing direct evidence for the formation of boron–interstitial clusters. By profiling the samples with secondary ion mass steptroscopy and comparing the results to spreading resistance measurements the degree of deactivation can be determined. © 1999 American Institute of Physics.  
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61.72.Yx Interaction between different crystal defects; gettering effect
61.72.J- Point defects and defect clusters
61.80.Jh Ion radiation effects
61.72.Cc Kinetics of defect formation and annealing
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.S- Impurities in crystals
61.82.Fk Semiconductors
61.72.uf Ge and Si

Self-assembled InSb quantum dots grown on GaSb: A photoluminescence, magnetoluminescence, and atomic force microscopy study

E. Alphandéry, R. J. Nicholas, N. J. Mason, B. Zhang, P. Möck, and G. R. Booker

Appl. Phys. Lett. 74, 2041 (1999); http://dx.doi.org/10.1063/1.123750 (3 pages) | Cited 34 times

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We report a study of self-assembled quantum dots (QDs) of InSb embedded in a GaSb matrix grown by metalorganic vapor phase deposition. Growth temperatures and deposition times have been optimized for maximal photoluminescence peak intensities. Photoluminescence (PL), magneto-PL, and atomic force microscopy (AFM) have been performed to estimate the size of the QDs. The quantum dots luminesce in the midinfrared at around 0.73 eV. The application of magnetic fields up to 15 T both parallel and perpendicular to the growth direction enhanced the wetting layer and bulk PL intensity and enabled an estimate to be made of the QD height and widths as 2–4 and 20–30 nm, respectively. These sizes were confirmed by AFM. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.20.Ls Magneto-optical effects
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
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