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15 Sep 2003

Volume 94, Issue 6, pp. 3675-4231

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Time and real space dependence of impact ionization events in low noise impact avalanche transit time diodes

K. P. D. Lim, P. A. Childs, and D. C. Herbert

J. Appl. Phys. 94, 3897 (2003); http://dx.doi.org/10.1063/1.1595140 (4 pages)

Online Publication Date: 29 August 2003

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Impact avalanche transit time (IMPATT) diodes are an important source of radio-frequency power at millimeter and submillimeter wavelengths. However, exploitation of these devices has been restricted, as they are commonly believed to suffer from high noise levels. In this article, we demonstrate that a heterostructure IMPATT diode has the potential for almost noise-free operation. Our analysis is based on a Monte Carlo simulation of oscillating IMPATT devices. © 2003 American Institute of Physics.
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
85.30.Kk Junction diodes
85.30.De Semiconductor-device characterization, design, and modeling

Photoluminescence fatigue and related degradation in thin-film photovoltaics

Diana Shvydka, C. Verzella, V. G. Karpov, and A. D. Compaan

J. Appl. Phys. 94, 3901 (2003); http://dx.doi.org/10.1063/1.1601687 (6 pages) | Cited 4 times

Online Publication Date: 29 August 2003

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We observe that junction photoluminescence (PL) intensity excited by a constant power laser beam in polycrystalline CdTe/CdS solar cells gradually decreases, which is similar to the PL fatigue in chalcogenide glasses. As a function of time, it was studied at different laser beam powers and temperatures for contact-free and metallized regions. We were able to discriminate between the fatigue per se and a concomitant short-time PL intensity drop due to the laser heating. The fatigue shows substantial variations between different spots on the sample. It is more profound at higher temperatures and laser beam powers where its value can be as large as 80% in 2 h. At low temperatures and beam powers, it saturates rather quickly not exceeding 10% of the initial PL intensity. We attribute the observed phenomenon to defect creation by the light-generated electrons and holes. The defects provide additional nonradiative recombination channels thus decreasing the PL. Simultaneously, this negative feedback makes the defect-generation rate slow down, so that the PL fatigue saturates. We propose a simple analytical model that fits the data. © 2003 American Institute of Physics.
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84.60.Jt Photoelectric conversion
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors

Pulsed laser deposition of Bi2Te3-based thermoelectric thin films

Raghuveer S. Makala, K. Jagannadham, and B. C. Sales

J. Appl. Phys. 94, 3907 (2003); http://dx.doi.org/10.1063/1.1600524 (12 pages) | Cited 34 times

Online Publication Date: 29 August 2003

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Thin films of p-type Bi0.5Sb1.5Te3, n-type Bi2Te2.7Se0.3, and n-type (Bi2Te3)90(Sb2Te3)5(Sb2Se3)5 (with 0.13 wt % SbI3) were deposited on substrates of mica and aluminum nitride (on silicon) using pulsed laser ablation at substrate temperatures between 300 °C to 500 °C. The films were characterized using x-ray diffraction and transmission electron microscopy for crystalline quality and epitaxial growth on the substrates. The surface morphology and microstructure were examined using scanning electron microscopy. X-ray mapping and energy-dispersive spectroscopy were performed to determine nonstoichiometry in the composition and homogeneity. The quality of the films, in terms of stoichiometric composition and crystal perfection, was studied as a function of growth temperature and laser fluence. The values of the Seebeck coefficient, electrical resistivity, and Hall mobility in the thin films were measured and compared with those in the bulk. Thermoelectric figure of merit of the films was evaluated from the measured parameters. Correlation of the thermoelectric properties, with the crystalline quality and stoichiometric composition of the films, showed the advantages of pulsed laser deposition of the multicomponent thermoelectric thin films. The results illustrate that laser physical vapor deposition is a suitable choice for deposition of multicomponent thermoelectric films. However, optimization of target composition, substrate temperature, and annealing of the films after deposition were found necessary to maintain the desired stoichiometry and low defect density. AlN/Si substrates provided better quality films compared to substrates of mica. Poor adhesion and cracking of the films on mica were found to be detrimental factors. Films deposited on AlN/Si substrates were found to show higher carrier mobility and higher values of Seebeck coefficient. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
72.20.Pa Thermoelectric and thermomagnetic effects
73.61.Le Other inorganic semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
68.37.Lp Transmission electron microscopy (TEM)
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments

Electronic structure of thin film silicon oxynitrides measured using soft x-ray emission and absorption

Cormac McGuinness, Dongfeng Fu, James E. Downes, Kevin E. Smith, Gregory Hughes, and Jason Roche

J. Appl. Phys. 94, 3919 (2003); http://dx.doi.org/10.1063/1.1599629 (4 pages) | Cited 12 times

Online Publication Date: 29 August 2003

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The elementally resolved electronic structure of a thin film silicon oxynitride gate dielectric used in commercial device fabrication has been measured using soft x-ray emission and absorption spectroscopies. The SiOxNy was grown by annealing SiO2 in NH3. Soft x-ray emission and soft x-ray absorption were used to measure the valence and conduction band partial density of states in the interfacial region of both the nitrogen and oxygen states. The elementally specific band gap for the O 2p states was measured to be 8.8 eV in the interfacial region, similar to that of pure SiO2. The elementally specific band gap for the N 2p states in the interfacial region was measured to be approximately 5 eV. © 2003 American Institute of Physics.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
71.20.Ps Other inorganic compounds
77.55.-g Dielectric thin films
78.70.En X-ray emission spectra and fluorescence
78.70.Dm X-ray absorption spectra
61.72.Cc Kinetics of defect formation and annealing

Electrically active sulfur-defect complexes in sulfur implanted diamond

R. Kalish, C. Uzan-Saguy, R. Walker, and S. Prawer

J. Appl. Phys. 94, 3923 (2003); http://dx.doi.org/10.1063/1.1598637 (8 pages) | Cited 7 times

Online Publication Date: 29 August 2003

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Single crystal type IIa 〈100〉 diamonds were implanted with sulfur, phosphorus, and argon ions under different implantation and annealing conditions. Shallow (sub-MeV) as well as deep (MeV) implantations into samples held at low (liquid nitrogen) ambient (room temperature) and high (400 °C) temperatures were employed. The implanted samples were subjected to postimplantation annealing up to 1000 °C. Following each processing step the samples were subjected to (i) Raman spectroscopy, in order to investigate the implantation related residual defects, and (ii) electrical (resistivity and sometimes Hall effect) measurements as function of temperature. The correlation between the results of these structural and electrical measurements and the comparison of results obtained under identical processing conditions for possible n-type dopant ion-implantations (S and P) and inert (Ar) ion-implantations, as controls, leads to the following conclusions: (a) Sulfur implanted samples always exhibit at least one order of magnitude higher conductivity than Ar control implanted samples. The activation energy associated with the S related conductivity is 0.32–0.37 eV whereas that of the Ar control is 0.5 to 0.6 eV. Hall effect shows, for selected cases, n-type conductivity with low carrier concentration and mobility. (b) Although the presence of some residual defects (mainly split interstitials) seems to accompany the appearance of the S related electrical activity, the level of residual damage in the S implanted samples is always less than that of the Ar control. (c) The electrical effects due to the implantation of S vanish upon annealing at temperatures in access of 800 °C. (d) No significant difference in the electrical properties between P and control Ar implantations are evident. It is concluded that a sulfur-defect related complex, which decomposes at T>800 °C, is responsible for the electrical effects in S implanted diamond. The presence of B contamination which has complicated the interpretation of experiments involving S doping during chemical vapor deposition diamond growth is excluded in the present work in which ion-implantation doping was employed.© 2003 American Institute of Physics.
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61.72.Yx Interaction between different crystal defects; gettering effect
72.80.Cw Elemental semiconductors
61.72.up Other materials
61.72.J- Point defects and defect clusters
78.30.Am Elemental semiconductors and insulators
72.20.My Galvanomagnetic and other magnetotransport effects
72.20.Fr Low-field transport and mobility; piezoresistance
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors

Band line-up determination at p- and n-type Al/4H-SiC Schottky interfaces using photoemission spectroscopy

J. Kohlscheen, Y. N. Emirov, M. M. Beerbom, J. T. Wolan, S. E. Saddow, G. Chung, M. F. MacMillan, and R. Schlaf

J. Appl. Phys. 94, 3931 (2003); http://dx.doi.org/10.1063/1.1599050 (8 pages) | Cited 13 times

Online Publication Date: 29 August 2003

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The band lineup of p- and n-type 4H–SiC/Al interfaces was determined using x-ray photoemission spectroscopy (XPS). Al was deposited in situ on ex situ cleaned SiC substrates in several steps starting at 1.2 Å up to 238 Å nominal film thickness. Before growth and after each growth step, the sample surface was characterized in situ by XPS. The analysis of the spectral shifts indicated that during the initial deposition stages the Al films react with the ambient surface contamination layer present on the samples after insertion into vacuum. At higher coverage metallic Al clusters are formed. The band lineups were determined from the analysis of the core level peak shifts and the positions of the valence bands maxima (VBM) depending on the Al overlayer thickness. Shifts of the Si 2p and C 1s XPS core levels occurred to higher (lower) binding energy for the p-(n-)type substrates, which was attributed to the occurrence of band bending due to Fermi-level equilibration at the interface. The hole injection barrier at the p-type interface was determined to be 1.83±0.1 eV, while the n-type interface revealed an electron injection barrier of 0.98±0.1 eV. Due to the weak features in the SiC valence bands measured by XPS, the VBM positions were determined using the Si 2p peak positions. This procedure required the determination of the Si 2p-to-VBM binding energy difference (99.34 eV), which was obtained from additional measurements. © 2003 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
73.61.Le Other inorganic semiconductors
79.60.Jv Interfaces; heterostructures; nanostructures
73.20.At Surface states, band structure, electron density of states

Electrical and chemical characterization of the Schottky barrier formed between clean n-GaN(0001) surfaces and Pt, Au, and Ag

K. M. Tracy, P. J. Hartlieb, S. Einfeldt, R. F. Davis, E. H. Hurt, and R. J. Nemanich

J. Appl. Phys. 94, 3939 (2003); http://dx.doi.org/10.1063/1.1598630 (10 pages) | Cited 40 times

Online Publication Date: 29 August 2003

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Platinum, gold, and silver formed abrupt, unreacted, smooth, and epitaxial metal–semiconductor interfaces when deposited from the vapor onto clean, n-type GaN(0001) films. The Schottky barrier heights, determined from data acquired using x-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, capacitance–voltage, and current–voltage measurements agreed to within the experimental error for each contact metal and had the values of 1.2±0.1, 0.9±0.1, and 0.6±0.1 eV for Pt, Au, and Ag, respectively. The band bending and the electron affinity at the clean n-GaN surface were 0.3±0.1 and 3.1±0.1 eV, respectively. The barrier height is proportional to the metal work function, indicating that the Fermi level is not pinned at the GaN surface. However, discrepancies to the Schottky–Mott model were found as evidenced by a proportionality factor of 0.44 between the work function of the metal and the resulting Schottky barrier height. The sum of these discrepancies constitute the interface dipole contributions to the Schottky barrier height which were measured to be ∼1.4, 1.3, and 0.7 eV for Pt, Au, and Ag, respectively. © 2003 American Institute of Physics.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
79.60.Jv Interfaces; heterostructures; nanostructures

Band offset measurements of the Si3N4/GaN (0001) interface

T. E. Cook, C. C. Fulton, W. J. Mecouch, R. F. Davis, G. Lucovsky, and R. J. Nemanich

J. Appl. Phys. 94, 3949 (2003); http://dx.doi.org/10.1063/1.1601314 (6 pages) | Cited 20 times

Online Publication Date: 29 August 2003

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X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy were used to measure electronic states as Si3N4 was deposited on clean GaN (0001) surfaces. The n-type (2×1018) and p-type (1×1017) GaN surfaces were atomically cleaned in NH3 at 860 °C, and the n-and p-type surfaces showed upward band bending of ∼0.2±0.1 eV and downward band bending of 1.1±0.1 eV, respectively, both with an electron affinity of 3.1±0.1 eV. Layers of Si (∼0.2 nm) were deposited on the clean GaN and nitrided using an electron cyclotron resonance N2 plasma at 300 °C and subsequently annealed at 650 °C for densification into a Si3N4 film. Surface analysis was performed after each step in the process, and yielded a valence band offset of 0.5±0.1 eV. Both interfaces exhibited type II band alignment where the valence band maximum of GaN lies below that of the Si3N4 valence band. The conduction band offset was deduced to be 2.4±0.1 eV, and a change of the interface dipole of 1.1±0.1 eV was observed for Si3N4/GaN interface formation. © 2003 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
79.60.Jv Interfaces; heterostructures; nanostructures
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.72.Cc Kinetics of defect formation and annealing

Determination of band offsets in semiconductor quantum well structures using surface photovoltage

Gh. Dumitras and H. Riechert

J. Appl. Phys. 94, 3955 (2003); http://dx.doi.org/10.1063/1.1603346 (5 pages) | Cited 16 times

Online Publication Date: 29 August 2003

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Surface photovoltage in semiconductor single quantum well structures is studied. The surface photovoltage spectra of such structures contain the essential information to enable the determination of band offsets. To estimate the band offsets only one sample is necessary, which is an advantage over other methods. The cases of type I- and type II-band alignment are discussed separately. Two particular single quantum well samples are studied by this measurement method. GaAs/In0.65Ga0.35As0.983N0.017/GaAs and GaAs/Ga0.7As0.3Sb/GaAs which are of type I and type II, respectively. The values 79/21 (type I) and 12/88 (type II) are obtained for the conduction/valence-band ratio ΔEC/ΔEV in the InGaAsN and GaAsSb quantum well structures, respectively. © 2003 American Institute of Physics.
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73.21.Fg Quantum wells
81.07.St Quantum wells
81.05.Ea III-V semiconductors
73.63.Hs Quantum wells
71.20.Nr Semiconductor compounds
72.40.+w Photoconduction and photovoltaic effects
73.25.+i Surface conductivity and carrier phenomena

Hydrogen plasma passivation effects on properties of p-GaN

A. Y. Polyakov, N. B. Smirnov, A. V. Govorkov, K. H. Baik, S. J. Pearton, B. Luo, F. Ren, and J. M. Zavada

J. Appl. Phys. 94, 3960 (2003); http://dx.doi.org/10.1063/1.1603343 (6 pages) | Cited 11 times

Online Publication Date: 29 August 2003

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The effects of hydrogen on the electrical and optical properties of p-GaN were investigated. Hydrogen is readily incorporated into the material at temperatures of 250–350 °C, which is consistent with the low activation energy for diffusion reported by Seager et al. [J. Appl. Phys. 92, 7246 (2002)] in GaN p-n junctions. From comparison with the results of earlier experiments, hydrogen diffusivity appears to be a strong function of the hydrogen concentration incorporated into the material during growth. More than an order of magnitude decrease in hole concentration was observed after the hydrogen plasma treatment and from the measurements of the temperature dependence of conductivity. This is the result of hydrogen passivation of acceptors rather than of increased compensation by donor centers. Hydrogen treatment was also shown to lead to a strong suppression of 0.3 eV and 0.6 eV traps and to a strong increase in the magnitude of the photocurrent which are the results of passivation of deep-level defects by hydrogen. At the same time, hydrogen plasma treatment led to a strong increase in the concentration of 0.4 eV hole traps. © 2003 American Institute of Physics.
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81.65.Rv Passivation
81.05.Ea III-V semiconductors
68.47.Fg Semiconductor surfaces
71.55.Eq III-V semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Ey III-V and II-VI semiconductors
52.77.-j Plasma applications
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.40.+w Photoconduction and photovoltaic effects

Arsenic pressure dependence of carrier lifetime and annealing dynamics for low-temperature grown GaAs studied by pump–probe spectroscopy

R. Yano, Y. Hirayama, S. Miyashita, N. Uesugi, and S. Uehara

J. Appl. Phys. 94, 3966 (2003); http://dx.doi.org/10.1063/1.1602569 (6 pages) | Cited 7 times

Online Publication Date: 29 August 2003

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Reflection-type degenerate pump-probe spectroscopy was performed for low-temperature grown (LT-) GaAs to study the effects of arsenic pressure during crystal growth and annealing on carrier lifetime and to ascertain the annealing dynamics. It was found that a sample grown under a high arsenic pressure has a shorter carrier lifetime for both as-grown and anneal conditions. It was also found that the carrier decay times of samples changed drastically when the annealing temperature was above 550 °C. We determined the annealing dynamics of LT-GaAs based on a model in which AsGa antisite defects trap photoexcited carriers. An Arrhenius plot of the carrier decay rate vs. annealing temperature in the high temperature regime gave an energy EPA that was different from the true activation energy. The annealing time dependences of EPA obtained by the two diffusion models (self diffusion and VGa vacancy assisted diffusion of defects) were compared with EPAs of our data and other works, which proved that the annealing dynamics of AsGa antisite defects was dominated by VGa vacancy assisted diffusion. © 2003 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
61.72.Cc Kinetics of defect formation and annealing
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
61.72.J- Point defects and defect clusters
66.30.Lw Diffusion of other defects

Theoretical model for polarization superlattices: Energy levels and intersubband transitions

B. K. Ridley, W. J. Schaff, and L. F. Eastman

J. Appl. Phys. 94, 3972 (2003); http://dx.doi.org/10.1063/1.1601686 (7 pages) | Cited 20 times

Online Publication Date: 29 August 2003

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A theoretical model for stress-free polarization superlattices composed of wurtzite semiconductors is described, which exploits Airy function solutions of the Schrödinger equation for a superlattice in the absence of free carriers. The theory is applied to several stress-free structures consisting of AlN barriers and GaN wells. The part played by the crystal-field splitting of the valence band and its dependence on biaxial elastic strain in determining the conduction-band offset is fully taken into account. Electric fields were determined from the spontaneous and nonlinear piezoelectric polarization. Energy bands, transition energies between subbands 1 and 2, and associated eigenfunctions are calculated, and the sensitivity to the conduction-band discontinuity explored. Intersubband radiative and nonradiative transition rates are estimated taking into account the Bloch-function overlap integrals and the role of intervalley scattering. Upper limits to technologically useful subband separations set by conduction-band offsets and the energy of conduction-band valleys are discussed. An upper limit of around 1.5 eV for the energy of the second subband is indicated. © 2003 American Institute of Physics.
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73.21.Cd Superlattices
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
77.22.Ej Polarization and depolarization
77.65.Ly Strain-induced piezoelectric fields
71.70.Ch Crystal and ligand fields

Noise power spectrum of a long-channel current line with electron traps: Slave-boson mean field theory

Tetsufumi Tanamoto, Ryuji Ohba, Ken Uchida, and Shinobu Fujita

J. Appl. Phys. 94, 3979 (2003); http://dx.doi.org/10.1063/1.1603342 (5 pages) | Cited 1 time

Online Publication Date: 29 August 2003

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We calculated the noise power spectrum of a one-dimensional free electron system corresponding to a long-channel current line when there are several electron traps near the current line. The calculation was performed starting from the Anderson Hamiltonian in the framework of the slave-boson mean field theory. When there is a single trap, the noise power spectrum shows a peak structure. When there are two traps and the distance between the two traps is less than the Fermi momentum, the peak of the noise power is enhanced because of interference between the two traps. When there are multiple traps, the noise power is analytically found to have an ω−2 dependence in the low-frequency limit and an ω−1/2 dependence in the high-frequency limit. These results are applicable to the noise analysis of nanodevices such as a single-electron transistor (SET) if the traps are regarded as the SET islands. © 2003 American Institute of Physics.
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72.70.+m Noise processes and phenomena
85.35.Gv Single electron devices
85.65.+h Molecular electronic devices
85.30.De Semiconductor-device characterization, design, and modeling
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.10.Pm Fermions in reduced dimensions (anyons, composite fermions, Luttinger liquid, etc.)
73.23.-b Electronic transport in mesoscopic systems
73.63.-b Electronic transport in nanoscale materials and structures

Effect of electromechanical coupling on the strain in AlGaN/GaN heterojunction field effect transistors

B. Jogai, J. D. Albrecht, and E. Pan

J. Appl. Phys. 94, 3984 (2003); http://dx.doi.org/10.1063/1.1603953 (6 pages) | Cited 20 times

Online Publication Date: 29 August 2003

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The strain in AlGaN/GaN heterojunction field-effect transistors (HFETs) is examined theoretically in the context of the fully coupled equation of state for piezoelectric materials. Using a simple analytical model, it is shown that, in the absence of a two-dimensional electron gas (2DEG), the out-of-plane strain obtained without electromechanical coupling is in error by about 30% for an Al fraction of 0.3. This result has consequences for the calculation of quantities that depend directly on the strain tensor. These quantities include the eigenstates and electrostatic potential in AlGaN/GaN heterostructures. It is shown that for an HFET, the electromechanical coupling is screened by the 2DEG. Results for the electromechanical model, including the 2DEG, indicate that the standard (decoupled) strain model is a reasonable approximation for HFET calculations. The analytical results are supported by a self-consistent Schrödinger–Poisson calculation that includes the fully coupled equation of state together with the charge-balance equation. © 2003 American Institute of Physics.
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77.65.Ly Strain-induced piezoelectric fields
77.65.Bn Piezoelectric and electrostrictive constants
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
85.30.Tv Field effect devices

Spin-polarized electron tunneling across a Si delta-doped GaMnAs/n-GaAs interface

S. E. Andresen, B. S. Sørensen, F. B. Rasmussen, P. E. Lindelof, J. Sadowski, C. M. Guertler, and J. A. C. Bland

J. Appl. Phys. 94, 3990 (2003); http://dx.doi.org/10.1063/1.1602945 (5 pages) | Cited 2 times

Online Publication Date: 29 August 2003

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We study the spin-polarized tunneling of electrons from the valence band of GaMnAs into the conduction band of n-type GaAs with Si delta-doping at the interface. The injection of spin-polarized electrons is detected as circular polarized emission from a GaInAs/GaAs quantum well light emitting diode, corresponding to magneto-optical Kerr effect loops. The angular momentum selection rules are simplified by the strain-induced heavy-hole/light-hole splitting, allowing a direct relation between circular polarization and spin-polarization. Comparison with the influence of Zeeman splitting allow us to conclude a spin-injection from the majority spin-band. © 2003 American Institute of Physics.
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72.25.Mk Spin transport through interfaces
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
75.50.Pp Magnetic semiconductors
61.72.S- Impurities in crystals
75.47.Pq Other materials
85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.07.St Quantum wells
78.67.De Quantum wells
73.63.Hs Quantum wells
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
78.20.Ls Magneto-optical effects
85.75.Mm Spin polarized resonant tunnel junctions

Composition dependence of the interband critical points in Si1−xGex alloys: A fractional–dimensional space approach

Keyu Tao, Yueli Zhang, Dang Mo, Naokatsu Sano, and Tadaaki Kaneko

J. Appl. Phys. 94, 3995 (2003); http://dx.doi.org/10.1063/1.1604478 (6 pages) | Cited 1 time

Online Publication Date: 29 August 2003

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The fractional–dimensional space approach is used to analyze the compositional dependence of direct interband transitions in Si1−xGex. The pertinent critical point (CP) parameters are obtained, and a CP structure, identified as E1′, is found. With regard to the CP energy, general agreement with the results obtained by the standard treatment is achieved. The other CP parameters, such as dimensionality, lifetime broadening, and amplitude, directly show an effect of a residual oxide overlayer. Our research shows that the fractional–dimensional space approach has the advantages of directness, flexibility, and sensitivity which provide a straightforward and rapid analysis of critical points, especially useful for deformed optical spectra. © 2003 American Institute of Physics.
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78.20.Bh Theory, models, and numerical simulation
71.20.Nr Semiconductor compounds
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