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29 Jun 1998

Volume 72, Issue 26, pp. 3399-3517

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Theoretical investigation of edge dislocations in AlN

A. F. Wright and J. Furthmüller

Appl. Phys. Lett. 72, 3467 (1998); http://dx.doi.org/10.1063/1.121668 (3 pages) | Cited 24 times

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The structures and formation energies of neutral and charged edge dislocations in AlN are investigated via density-functional-theory calculations. Stoichiometric structures having full and open cores are considered as well as nonstoichiometric structures having aluminum or nitrogen vacancies along the dislocation core. Formation energies are found to depend strongly on the Fermi level, due to the presence of defect levels in the band gap, and on growth conditions for the case of the nonstoichiometric structures. A structure having aluminum vacancies along the dislocation core is predicted to be most stable in n-type material grown under nitrogen-rich conditions, whereas a nitrogen-vacancy structure is most stable in p-type material grown under aluminum-rich conditions. Estimates are also given for defect energy levels in the gap. © 1998 American Institute of Physics.
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61.72.J- Point defects and defect clusters
61.72.Lk Linear defects: dislocations, disclinations
61.72.Bb Theories and models of crystal defects
61.66.Bi Elemental solids
61.66.Dk Alloys
71.20.Nr Semiconductor compounds
72.80.Ey III-V and II-VI semiconductors
71.55.Eq III-V semiconductors

Recombination lifetime of In0.53Ga0.47As as a function of doping density

R. K. Ahrenkiel, R. Ellingson, S. Johnston, and M. Wanlass

Appl. Phys. Lett. 72, 3470 (1998); http://dx.doi.org/10.1063/1.121669 (3 pages) | Cited 39 times

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We have fabricated devices with the structure InP/In0.53Ga0.47As/InP, with a InGaAs doping range varying from 2×1014 to 2×1019 cm−3. These isotype double heterostructures were doped both n and p type and were used to measure the minority-carrier lifetime of InGaAs over this doping range. At the low doping end of the series, recombination is dominated by the Shockley–Read–Hall effect. At the intermediate doping levels, radiative recombination is dominant. At the highest doping levels, Auger recombination dominates as the lifetime varies with the inverse square of the doping concentration. From fitting these data, the radiative- and Auger-recombination coefficients are deduced. © 1998 American Institute of Physics.
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72.80.Ey III-V and II-VI semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
79.20.Fv Electron impact: Auger emission

Efficient 300 K light-emitting diodes at λ ∼ 5 and ∼ 8 μm from InAs/In(As1−xSbx) single quantum wells

P. J. P. Tang, H. Hardaway, J. Heber, C. C. Phillips, M. J. Pullin, R. A. Stradling, W. T. Yuen, and L. Hart

Appl. Phys. Lett. 72, 3473 (1998); http://dx.doi.org/10.1063/1.121670 (3 pages) | Cited 15 times

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300 K light-emitting diodes which emit at 5 and 8 μm with quasi-cw output powers of up to 50 and 24 μW, respectively, are reported. The devices have a single molecular beam epitaxy grown InAs/In(As, Sb) quantum well in the active region with a strong type-IIa band alignment giving mid-IR emission at energies up to 64% lower than the alloy band gap. The emission energies are shown to be in good agreement with a k⋅p bandstructure model where Qc, the ratio of the strained conduction-band offset to the band-gap difference between the two strained superlattice components, is found to be ∼ 2.0. © 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.)
78.66.Fd III-V semiconductors
78.60.Fi Electroluminescence
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

Small signal electron charge centroid model for quantization of inversion layer in a metal-on-insulator field-effect transistor

Ya-Chin King, Chenming Hu, Hiroshi Fujioka, and Shiroo Kamohara

Appl. Phys. Lett. 72, 3476 (1998); http://dx.doi.org/10.1063/1.121671 (3 pages) | Cited 3 times

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A simulator using a coupled Schrödinger equation, Poisson equation and Fermi–Dirac statistics to analyze inversion layer quantization is shown to match the measured capacitance versus voltage data of thin oxide gate metal-on-insulator capacitance closely. The effects of bias voltage, oxide thickness and doping concentration on the charge centroid are presented. A simple empirical model for the alternating current charge centroid of the inversion layer is proposed. This model predicts the in-version layer capacitance or charge centroid in terms of Tox (oxide thickness), Vt (threshold voltage), and Vg (gate voltage) explicitly. © 1998 American Institute of Physics.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling

Effects of alloy ambient on PdGe contacts on n-type GaAs

D. A. Ahmari, M. L. Hattendorf, D. F. Lemmerhirt, Q. Yang, Q. J. Hartmann, J. E. Baker, and G. E. Stillman

Appl. Phys. Lett. 72, 3479 (1998); http://dx.doi.org/10.1063/1.121672 (3 pages) | Cited 3 times

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A high concentration of hydrogen in the alloy ambient slows the formation of PdGe contacts and increases the resistance of the PdGe to GaAs etchants. The effects of alloy ambient on alloy formation, specific contact resistance, and chemical reactivity of PdGe contacts on n-type GaAs have been studied. A very low specific contact resistance of <1×10−7 Ω cm2 has been achieved on GaAs with PdGe contacts alloyed at 300 °C for 15 min in a hydrogen ambient. These results indicate that PdGe may be a desirable contact for GaAs-based transistors. © 1998 American Institute of Physics.
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73.40.Cg Contact resistance, contact potential
73.40.Ns Metal-nonmetal contacts
73.61.Ey III-V semiconductors

Direct correlation of transition metal impurities and minority carrier recombination in multicrystalline silicon

Scott A. McHugo, A. C. Thompson, I. Périchaud, and S. Martinuzzi

Appl. Phys. Lett. 72, 3482 (1998); http://dx.doi.org/10.1063/1.121673 (3 pages) | Cited 40 times

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Impurity and minority carrier lifetime distributions were studied in as-grown multicrystalline silicon used for terrestrial-based solar cells. Synchrotron-based x-ray fluorescence and the light beam induced current technique were used to measure impurity and lifetime distributions, respectively. The purpose of this work was to determine the spatial relation between transition metal impurities and minority carrier recombination in multicrystalline silicon solar cells. Our results reveal a direct correlation between chromium, iron, and nickel impurity precipitates with regions of high minority carrier recombination. The impurity concentration was typically 5×1016 atoms/cm2, indicating the impurity-rich regions possess nanometer-scale precipitates. These results provide the first direct evidence that transition metal agglomerates play a significant role in solar cell performance. © 1998 American Institute of Physics.
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73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
84.60.Jt Photoelectric conversion
72.80.Cw Elemental semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

SiGe-based semiconductor-on-insulator substrate created by low-energy separation-by-implanted-oxygen

S. Fukatsu, Yukari Ishikawa, T. Saito, and N. Shibata

Appl. Phys. Lett. 72, 3485 (1998); http://dx.doi.org/10.1063/1.121674 (3 pages) | Cited 33 times

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SiGe-based semiconductor-on-insulator (SOI) substrates have been successfully created by the separation-by-implanted-oxygen technique. Low-energy oxygen ion implantation was performed at 25 kV on a strain-relieved Si0.82Ge0.18 virtual substrate grown on Si(001). A good SOI geometry with a 25-nm top SiGe layer was obtained over a dose window of 2–2.5×1017 cm−2, and a flat SiGe surface and sharp SiGe/SiO2 interfaces were achieved at a low substrate temperature of 550°C. Compositional analysis shows that the top SiGe layer nearly conserves the same composition as the underlying alloy substrate. © 1998 American Institute of Physics.
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61.72.uf Ge and Si
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.40.Ry Impurity doping, diffusion and ion implantation technology

Ion-beam synthesis and structural characterization of ZnS nanocrystals in SiO2

C. Bonafos, B. Garrido, M. López, A. Romano-Rodriguez, O. González-Varona, A. Pérez-Rodríguez, and J. R. Morante

Appl. Phys. Lett. 72, 3488 (1998); http://dx.doi.org/10.1063/1.121675 (3 pages) | Cited 10 times

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In this letter, we report the ion-beam synthesis and the structural characterization of ZnS nanocrystals in SiO2. Both electron diffraction and x-ray diffraction measurements show the precipitation of ZnS nanocrystals having a wurtzite–2H structure and infrared spectroscopy confirms the presence of Zn–S bonding. Upon annealing, transmission electron microscopy observations show the Ostwald ripening of the precipitates coupled with a self-organization in two layers parallel to the free surface. This self-organization has been also detected by secondary ion mass spectroscopy, and its origin is discussed in terms of a pure Ostwald ripening process and/or a consequence of the implantation damage. © 1998 American Institute of Physics.
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61.72.up Other materials
61.80.Jh Ion radiation effects
61.46.-w Structure of nanoscale materials
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
64.75.-g Phase equilibria
78.30.Fs III-V and II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing

Influence of partial dopant ionization on the capacitance–voltage profiles of delta-doped structures

C. R. Moon, S. D. Kwon, H. Lim, and Byung-Doo Choe

Appl. Phys. Lett. 72, 3491 (1998); http://dx.doi.org/10.1063/1.121676 (3 pages)

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The effects of partial dopant ionization on the capacitance–voltage (C–V) characteristics of δ-doped structures have been investigated using self-consistent simulations. The simulation results show that partially ionized δ-doped dopants should produce a much sharper C–V profile compared with the case of fully ionized dopants. The results reveal also that the main factor which determines the spatial resolution and the full width at half maximum of the C–V peak is the spatial extent of the dopant profile rather than the spatial extent of the ground-state wave function. From this, it is suggested that the δ-doped C–V data should be interpreted always with the effect of partial ionization of δ-doped dopants. © 1998 American Institute of Physics.
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61.72.S- Impurities in crystals
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
85.40.Ry Impurity doping, diffusion and ion implantation technology
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.55.-i Impurity and defect levels

Near-field optical spectroscopy and imaging of single InGaAs/AlGaAs quantum dots

A. Chavez-Pirson, J. Temmyo, H. Kamada, H. Gotoh, and H. Ando

Appl. Phys. Lett. 72, 3494 (1998); http://dx.doi.org/10.1063/1.121638 (3 pages) | Cited 31 times

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We use near-field optical probing at low temperatures (T = 5 K) to image and examine the linear and nonlinear luminescence properties of single InGaAs/AlGaAs quantum dots grown on (311)B oriented GaAs substrates. The high spatial resolution of near-field “nanoprobing,” which is typically 200 nm or less, makes the observation of single dots at different locations on the sample possible, even though the spatial density of quantum dots is on the order of 100/μm2. We observe narrow excitonic emission lines at low excitation powers and, with increasing excitation, we observe biexcitonic emission strongly shifted (3 meV) to the low-energy side of the exciton emission. © 1998 American Institute of Physics.
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73.61.Ey III-V semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
71.35.-y Excitons and related phenomena

Giant magnetoresistance enhancement in inhomogeneous semiconductors

Tineke Thio and S. A. Solin

Appl. Phys. Lett. 72, 3497 (1998); http://dx.doi.org/10.1063/1.121639 (3 pages) | Cited 19 times

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We show that the low-field magnetoresistance (MR) of a semiconductor with inhomogeneities which are more conducting than the surrounding matrix is enhanced significantly compared to that of the homogeneous material. The enhancement results from a magnetic field induced geometric effect in which at high field the current is deflected around the conducting inhomogeneity. A model based on previous work by Wolfe et al. has been augmented to include the physical MR. The augmented model is used to account quantitatively for a 50-fold anomalous enhancement of the giant magnetoresistance (GMR) observed at low field in (near) zero-band-gap thin-film Hg1−xCdxTe (x ≈ 0.1). The practical implications of the GMR boost are noted. © 1998 American Institute of Physics.
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73.61.Ga II-VI semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Fq High-field and nonlinear effects
72.20.My Galvanomagnetic and other magnetotransport effects
72.80.Ey III-V and II-VI semiconductors
72.20.Ht High-field and nonlinear effects

Enhanced stability of deuterium in silicon

R. Biswas, Y.-P. Li, and B. C. Pan

Appl. Phys. Lett. 72, 3500 (1998); http://dx.doi.org/10.1063/1.121640 (3 pages) | Cited 20 times

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Tight-binding molecular dynamics has been used to simulate vibrationally excited Si–H and Si–D modes. Simulations find that vibrationally excited Si–D bending modes decay much more rapidly than Si–H bending modes, resulting in SiD bonds having much higher stability than SiH bonds. This provides a viable mechanism for reduced degradation in deuterated metal–oxide–semiconductor transistors and deuterated amorphous silicon devices. © 1998 American Institute of Physics.
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61.72.uf Ge and Si
61.50.Lt Crystal binding; cohesive energy
63.20.-e Phonons in crystal lattices

p-n junction peripheral current analysis using gated diode measurements

A. Czerwinski, E. Simoen, and C. Claeys

Appl. Phys. Lett. 72, 3503 (1998); http://dx.doi.org/10.1063/1.121641 (3 pages) | Cited 5 times

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A modified method for analysis of the current–voltage characteristics of a gated diode structure is proposed and validated in order to investigate the peripheral reverse current in a silicon p-n junction diode. The peripheral generation current in modern p-n diodes is attributed fully to surface generation underneath the thick field oxide surrounding the structure, which typically contains a high density of interface traps. For a gated diode structure, the current region observed for large gate voltages, VG, is linked to the generation associated with the depletion at the Si-thick SiO2 interface. It will be shown that, compared to the classical analysis, this current step is a better alternative to assess the peripheral generation. The 25 times higher sensitivity of gated diode measurements in this mode allows one to reduce the test device perimeter and dimensions, without penalizing the measurement resolution for interface states. The main advantage of the proposed method is related to the fact that for the peripheral current extraction, only the measurement of one diode is needed instead of the tedious measurements and analyses of a set of diodes. © 1998 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.Kk Junction diodes

Quantized conductance in quantum wires with gate-controlled width and electron density

B. E. Kane, G. R. Facer, A. S. Dzurak, N. E. Lumpkin, R. G. Clark, L. N. Pfeiffer, and K. W. West

Appl. Phys. Lett. 72, 3506 (1998); http://dx.doi.org/10.1063/1.121642 (3 pages) | Cited 7 times

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We describe quantum wires and point contacts fabricated in GaAs/AlxGa1−xAs heterostructures that are free of the disorder introduced by modulation doping and in which the electron density and the confining potential are separately adjustable by lithographically defined gates. We observe conductance plateaus quantized near even multiples of e2/h in 2 μm wires and up to 15 conductance steps in 5 μm wires at temperatures below 1 K. Near the conductance threshold the quantum point contact and the 2 μm wire both show additional structure below 2e2/h. © 1998 American Institute of Physics.
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73.61.Ey III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.23.-b Electronic transport in mesoscopic systems

Characteristics of InAs/AlGaAs self-organized quantum dot modulation doped field effect transistors

J. Phillips, K. Kamath, T. Brock, and P. Bhattacharya

Appl. Phys. Lett. 72, 3509 (1998); http://dx.doi.org/10.1063/1.121643 (3 pages) | Cited 21 times

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We have investigated the dc characteristics of InGaAs/AlGaAs modulation doped field effect transistors in which a layer of self-organized InAs quantum dots is inserted adjacent to the pseudomorphic quantum well channel. Distinct steps and a negative differential resistance are observed in the current–voltage characteristics at room temperature and lower temperatures. These are attributed to conduction through the bound states in the quantum dots. © 1998 American Institute of Physics.
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73.61.Ey III-V semiconductors
85.30.Tv Field effect devices
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
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