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15 Mar 2000

Volume 87, Issue 6, pp. 2673-3189

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Reversible variation of donor concentrations in high-purity InP by thermal treatment

Eishi Kubota, Koshi Ando, and Syoji Yamada

J. Appl. Phys. 87, 2885 (2000); http://dx.doi.org/10.1063/1.372273 (5 pages) | Cited 1 time

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The donor concentration in high-purity InP bulk crystals was found to be reversibly changed by thermal treatment. At a level of 0.5–2.0×1015 cm−3, the concentration decreased below 340 °C and increased above 380 °C. Far-infrared photoconductivity measurements revealed that shallow donors with a binding energy of ∼7.5 meV were made to disappear and appear by low and high temperature treatment, respectively. Two possible mechanisms responsible for these phenomena are discussed in connection with the extrinsic and intrinsic donor origin. One probable mechanism is that shallow extrinsic donors, assigned to Si, are electrically passivated by some kind of defect, such as atomic hydrogen, and reactivated by low and high temperature treatment, respectively. © 2000 American Institute of Physics.
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71.55.Eq III-V semiconductors
72.40.+w Photoconduction and photovoltaic effects
72.80.Ey III-V and II-VI semiconductors

Empirical low-field mobility model for III–V compounds applicable in device simulation codes

M. Sotoodeh, A. H. Khalid, and A. A. Rezazadeh

J. Appl. Phys. 87, 2890 (2000); http://dx.doi.org/10.1063/1.372274 (11 pages) | Cited 41 times

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A Caughey–Thomas-like mobility model with temperature and composition dependent coefficients is used in this work to describe the dependence of electron and hole mobilities on temperature, doping concentration, and alloy composition. Appropriate parameter sets are given for a large number of III–V binary and ternary compounds, including: GaAs, InP, InAs, AlAs, GaP, Al0.3Ga0.7As, In0.52Al0.48As, In0.53Ga0.47As, and In0.49Ga0.51P. Additionally, physically justifiable interpolation schemes are suggested to find the mobilities of various ternary and quaternary compounds (such as AlxGa1−xAs, In1−xGaxP, In1−xGaxAs, In1−xAlxAs, and In1−xGaxAsyP1−y) in the entire range of composition. The models are compared with numerous measured Hall data in the literature and very good agreement is observed. The limitations of the present model are also discussed. The results of this work should be extremely useful in device simulation packages, which are currently lacking a reliable mobility model for the above materials. © 2000 American Institute of Physics.
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72.80.Ey III-V and II-VI semiconductors
72.20.Ee Mobility edges; hopping transport
72.20.Fr Low-field transport and mobility; piezoresistance
85.30.De Semiconductor-device characterization, design, and modeling
61.66.Bi Elemental solids
61.66.Dk Alloys
72.20.My Galvanomagnetic and other magnetotransport effects

Modulated photoconductivity study of electron drift mobility in amorphous silicon

K. Hattori, M. Iida, T. Hirao, and H. Okamoto

J. Appl. Phys. 87, 2901 (2000); http://dx.doi.org/10.1063/1.372275 (9 pages) | Cited 4 times

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The modulated photoconductivity technique, a convenient means of measuring the drift mobility of photocarriers, has been applied to investigate carrier transport in hydrogenated amorphous silicon. The frequency resolved spectra of drift mobility that can be obtained from the measurements were analyzed in accordance with a generalized transport model that included possible carrier interactions between localized states through tunneling transitions. Theory suggests that a tunneling-assisted thermalization of nonequilibrium carriers appreciably affects the transport process. The experimental results are reasonably accounted for by the introduced model, leading to quantitative assessments for transport mechanisms. © 2000 American Institute of Physics.
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72.80.Cw Elemental semiconductors
72.80.Ng Disordered solids
72.40.+w Photoconduction and photovoltaic effects
72.20.Ee Mobility edges; hopping transport
72.20.Fr Low-field transport and mobility; piezoresistance
71.55.Jv Disordered structures; amorphous and glassy solids
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Annealing kinetics of {311} defects and dislocation loops in the end-of-range damage region of ion implanted silicon

L. S. Robertson, K. S. Jones, L. M. Rubin, and J. Jackson

J. Appl. Phys. 87, 2910 (2000); http://dx.doi.org/10.1063/1.372276 (4 pages) | Cited 21 times

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The evolution of both {311} defects and dislocation loops in the end-of-range (EOR) damage region in silicon amorphized by ion implantation was studied by ex situ transmission electron microscopy (TEM). The amorphization of a (100) n-type Czochralski wafer was achieved with a 20 keV 1×1015/cm2 Si+ ion implantation. The post-implantation anneals were performed in a furnace at 750 °C for times ranging from 10 to 370 min. After annealing the specimen for 10 min, the microstructure showed a collection of both {311} defects and small dislocation loops. The evolution of a specific group of defects was studied by repeated imaging of the same region after additional annealing. Quantitative TEM showed that {311} defects followed one of two possible evolutionary pathways as annealing times progressed; unfaulting to form dislocation loops or dissolving and releasing interstitials. Results indicate that in this temperature regime, {311} defects are the preferential site for dislocation loop nucleation. © 2000 American Institute of Physics.
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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.uf Ge and Si
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors

Electrical conductivity effects in polyethylene terephthalate films

E. Neagu, P. Pissis, and L. Apekis

J. Appl. Phys. 87, 2914 (2000); http://dx.doi.org/10.1063/1.372277 (9 pages) | Cited 21 times

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Electrical conductivity effects in biaxially stretched polyethylene terephthalate (PET) films of 6 μm thickness and 68% degree of crystallinity were investigated by means of dielectric relaxation spectroscopy in the frequency range 10−2–106 Hz and at temperatures higher than the glass transition temperature (∼85 °C) up to 190 °C. The formalisms of complex permittivity, electric modulus, and impedance were employed to analyze the experimental data. The results are discussed in terms of dc conductivity, conductivity current relaxation, interfacial Maxwell–Wagner–Sillars polarization, ρ peak, space-charge polarization, and electrode polarization. They are compared with the predictions of models for the electrical and dielectric properties of ion-conducting polymers. The dc conductivity values determined from dc measurement, from ac conductivity plots and from complex impedance plots agree well with each other. Their temperature dependence is described by the Vogel–Tammann–Fulcher equation and classifies PET as a fragile system. © 2000 American Institute of Physics.
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73.61.Ph Polymers; organic compounds
77.22.Gm Dielectric loss and relaxation
77.22.Ch Permittivity (dielectric function)
77.22.Ej Polarization and depolarization
77.22.Jp Dielectric breakdown and space-charge effects

Effect of arsenic precipitates on Fermi level in GaAs grown by molecular-beam epitaxy at low temperature

Y. H. Chen, Z. G. Wang, and Z. Yang

J. Appl. Phys. 87, 2923 (2000); http://dx.doi.org/10.1063/1.372278 (3 pages) | Cited 3 times

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A simple model is presented to discuss the effect of As precipitates on the Fermi level in GaAs grown by molecular-beam epitaxy at low temperature (LT-GaAs). This model implements the compensation between point defects and the depletion of arsenic precipitates. The condition that the Fermi level is pinned by As precipitates is attained. The shifts of the Fermi level in LT-GaAs with annealing temperature are explained by our model. Additionally, the role of As precipitates in conventional semi-insulating GaAs is discussed. © 2000 American Institute of Physics.
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71.55.Eq III-V semiconductors
73.61.Ey III-V semiconductors
64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation
71.20.Nr Semiconductor compounds

Raman scattering from Ge nanostructures grown on Si substrates: Power and limitations

A. V. Kolobov

J. Appl. Phys. 87, 2926 (2000); http://dx.doi.org/10.1063/1.372279 (5 pages) | Cited 51 times

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The analysis of Raman spectra obtained for different germanium nanostructures grown on silicon substrates is presented. Comparison of these spectra with a Raman spectrum of a silicon wafer reveals a one-to-one correspondence of features located around 229, 300, and 435 cm−1. It is argued that the peaks observed at these frequencies and often ascribed to Ge nanostructures are, in fact, coming from the Si substrate. The erroneous ascription of the peaks makes the corresponding conclusions incorrect. © 2000 American Institute of Physics.
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78.66.Db Elemental semiconductors and insulators
78.30.Am Elemental semiconductors and insulators
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Schottky barrier studies on single crystal ZnTe and determination of interface index

S. Bhunia and D. N. Bose

J. Appl. Phys. 87, 2931 (2000); http://dx.doi.org/10.1063/1.372280 (5 pages) | Cited 4 times

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Detailed studies on metal-(111) p-ZnTe Schottky barriers have been carried out using In, Ag, Al, and Cu as barrier metals. Weak dependence of barrier height on metal work function was observed. The highest and lowest barrier heights of 0.99 and 0.80 eV were found for In and Cu respectively which had lowest and highest work functions. The ideality factor n was found to vary between 1.84 for In and 2.13 for Al contacts. The Fermi level was found to be pinned effectively by interface states, the density of which was calculated to be 4.7×1013 states/cm2/eV. From the current–voltage characteristics measured between 250 and 350 K, the effective Richardson constant A∗∗ was determined to be 72±6 A/cm2/K2. This agrees very well with the theoretically calculated value of A∗∗ for a hole effective mass mh∗=0.6m0. The temperature variation of barrier height was also determined from the capacitance–voltage characteristics. The interface index a parameter used to describe the pinning strength of semiconductors was found to be 0.34 for ZnTe. © 2000 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
73.30.+y Surface double layers, Schottky barriers, and work functions
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
73.20.At Surface states, band structure, electron density of states

Intersubband electroabsorption spectra of semiconductor quantum wells

David M.-T. Kuo and Yia-Chung Chang

J. Appl. Phys. 87, 2936 (2000); http://dx.doi.org/10.1063/1.372281 (5 pages) | Cited 1 time

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The electroabsorption spectra of semiconductor quantum wells due to intersubband (including bound to continuum) transitions are studied theoretically within the effective-mass model. Interesting oscillatory behavior in the absorption spectra due to the Franz–Keldysh effect is explored. The calculated absorption spectra due to the electric field modulation are found in good agreement with available experimental data. © 2000 American Institute of Physics.
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78.20.Jq Electro-optical effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.66.Fd III-V semiconductors
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Pressure sensors based on silicon doped GaAs–AlAs superlattices

J. L. Robert, F. Bosc, J. Sicart, V. Mosser, and J. Lasseur

J. Appl. Phys. 87, 2941 (2000); http://dx.doi.org/10.1063/1.372282 (6 pages) | Cited 2 times

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We show how GaAs–AlAs short period superlattices, in place of AlGaAs thin layers, improve the performances of n-type III–V semiconductors as pressure sensing material. Pressure induced electron capture on relaxed silicon donor sites (so called DX center) is responsible for the high pressure coefficient of resistance (30% per kbar). In comparison to AlGaAs, band gap engineering is employed to optimize both pressure and temperature sensitivities of GaAs–AlAs pseudoalloys between 0 and 200 °C under pressures up to 2000 bars. An electrical characterization is made by performing resistance and Hall effect measurements as functions of hydrostatic pressure and temperature on two microstructures forming the monolithic transducer. The heterostructures consist of (GaAs)9–(AlAs)4 superlattices doped with silicon at concentrations of 1.4×1017 and 2×1018 cm−3, respectively. Accurate pressure measurements (resolution less than 0.2 bar) are performed on two resistors patterned on these microstructures. Monolithic microsensors can be designed on such a stacked GaAs–AlAs two-resistor microstructure. © 2000 American Institute of Physics.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
73.61.Ey III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
72.20.My Galvanomagnetic and other magnetotransport effects
07.07.Mp Transducers

Multiquantum well gain modeling using a Green’s function-based fractional dimensional approach

M. Vallone, D. Campi, and C. Cacciatore

J. Appl. Phys. 87, 2947 (2000); http://dx.doi.org/10.1063/1.372283 (9 pages) | Cited 3 times

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In this article we investigate semiconductor optical amplifiers (SOAs), based on strained InGaAs quantum wells. Their optical properties are computed and discussed using a new, analytical model of the gain, based on a Green’s function formalism developed in a space with a noninteger effective dimensionality, comprised between 2 and 3. Starting from the Bethe Salpeter Equation, a closed-form expression for the interband density of states in presence of carrier plasma of arbitrary density is obtained. The influence of the nonperfect two-dimensionality of quantum wells is shown to have a great influence on gain and ASE spectral shapes, making it necessary to account for it in most cases of practical interest. Experimental optical properties of SOAs are reported and modeled in the described formalism. © 2000 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Optical properties of InGaAs/InAIAs diffused double quantum wells

Wallace C. H. Choy

J. Appl. Phys. 87, 2956 (2000); http://dx.doi.org/10.1063/1.372284 (11 pages) | Cited 5 times

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The effects of interdiffusion on the subbands and optical properties of InGaAs/InAIAs double quantum well (QW) have been theoretically studied. The results show that since a double QW (DQW) can be diffused to become an effectively single QW structure, the characteristic features in the subbands structure and optical properties of a strongly coupled DQW structure and that of a single QW structure can be obtained by a suitable annealing time. Moreover, the increase in separation between the first symmetric and antisymmetric heavy hole subbands and the increase in the spin splitting of the valence subbands of the diffused DQW, due to an applied electric field, diminish when annealing time increases. In optimizing the In0.53(AlaGa1−a)0.47As/In0.52Al0.48As DQW structure, the results show that symmetric DQW with no Al content in wells can provide large material gain and radiative spontaneous recombination rate. With interdiffusion, the material gain and recombination rate reduce but the reduction saturates when the DQW structure is diffused to effectively become a single graded QW. By subjecting the DQW and an as-grown single QW to the same annealing conditions (where the summation of the width of the two wells and the separation barrier of the DQW equals the well width of the single QW), the diffused DQW can provide a larger material gain and radiative recombination rate than the diffused single QW when the annealing time is short. Therefore, the short-time diffused DQW is more useful for laser applications. Besides, since Al diffuses into the wells, the transition energy of the QW structure increases so that the operating wavelength of the optical devices can be adjusted. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
78.40.Fy Semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.72.Cc Kinetics of defect formation and annealing
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation

Mechanism for the generation of interface state precursors

J. F. Zhang, H. K. Sii, R. Degraeve, and G. Groeseneken

J. Appl. Phys. 87, 2967 (2000); http://dx.doi.org/10.1063/1.372285 (11 pages) | Cited 16 times

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The generation of interface states plays an important role in the degradation of submicrometer devices. Previous attention was mainly focused on the conversion between interface states and their precursors. The total number of defects, which is the sum of precursors and interface states, is often implicitly assumed to be constant. However, recent work indicates that this number could be increased. The mechanism for the generation of new precursors is still not clear and the objective of this article is to throw light on it. The work is concentrated on investigating the roles played by hydrogen and the holes trapped in the oxide. It is found that, although the H2 or the trapped hole alone does not create precursors, their simultaneous presence causes the damage. The hydrogen species can be either supplied externally or released within the device. The generation is thermally activated, but saturates at a defect-limited level. The generation kinetics is studied and the rate limiting mechanism is discussed. Efforts have been made to unveil the differences between the generated precursors and those originally in the device, in terms of their existing forms, thermal stability, annealing behavior, dependence on the hole fluence, and the hydrogen involvement. It is concluded that they originate from different defects. © 2000 American Institute of Physics.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling
73.20.At Surface states, band structure, electron density of states
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