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15 Jan 2008

Volume 103, Issue 2, Articles (02xxxx)

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Degradation of GaN-based quantum well light-emitting diodes

L. X. Zhao, E. J. Thrush, C. J. Humphreys, and W. A. Phillips

J. Appl. Phys. 103, 024501 (2008); http://dx.doi.org/10.1063/1.2829781 (6 pages) | Cited 6 times

Online Publication Date: 17 January 2008

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Electrical and optical properties of AlGaN/InGaN-based near-ultraviolet (UV) multiquantum well light-emitting diodes have been studied during operation at high junction temperatures. Light output decreased exponentially by 40% in the first 30 h after which there was no obvious change. The current-voltage characteristics were almost ideal before degradation, with an ideality factor of approximately 2. During degradation, an additional contribution to the current becomes apparent at voltages of below 2.5 V, with a temperature-independent logarithmic slope of the current-voltage characteristic, suggesting an additional transport mechanism by tunneling through defects created during degradation. The evolution of the additional current component corresponded to the two different stages observed in the reduction of the light emission with stress time. Generation of defects with similar effects on forward and reverse bias currents could be correlated with the rapid degradation during the first 30 h, but for the second stage, the change in the I-V characteristics did not correlate with the change in light emission. Electroluminescence spectra showed that the emission peaks shifted to slightly lower energies during degradation.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.40.Gk Tunneling

Monte Carlo analysis of noise spectra in self-switching nanodiodes

I. Iñiguez–de-la-Torre, J. Mateos, D. Pardo, and T. González

J. Appl. Phys. 103, 024502 (2008); http://dx.doi.org/10.1063/1.2832505 (6 pages) | Cited 8 times

Online Publication Date: 18 January 2008

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By means of a semiclassical two-dimensional Monte Carlo technique, we analyze current noise spectra of InAlAs/InGaAs-based submicron self-switching diodes. Shot noise (at low bias) and diffusion noise in the series resistance (at high bias) are found to dominate the current noise at low frequency (in the plateau beyond the 1/f range). Two peaks of different origins, which may limit the device performance, are found in the noise spectra at higher frequencies. The dependence of the amplitude and frequency of these peaks on the topology of the diodes is analyzed and discussed. Design indications to improve the noise performance of the devices are provided.
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85.30.Kk Junction diodes
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
85.35.-p Nanoelectronic devices

Implications of changes in the injection mechanisms on the low temperature electroluminescence in InGaN/GaN light emitting diodes

M. Pavesi, M. Manfredi, F. Rossi, M. Meneghini, G. Meneghesso, E. Zanoni, and U. Zehnder

J. Appl. Phys. 103, 024503 (2008); http://dx.doi.org/10.1063/1.2831226 (5 pages) | Cited 1 time

Online Publication Date: 22 January 2008

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The presence of traps is sometimes favorable, and sometimes detrimental to the electrical transport and optical efficiency in III-nitride quantum heterostructures. This work presents the results of a joint analysis of electrical features and electroluminescence in InGaN/GaN-based blue light emitting diodes; a detailed and exhaustive reading of the carrier injection mechanisms highlights the central role of trap centers near the active region. Some suggestions will be eventually advanced as to the design of devices with better emission performances.
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85.60.Jb Light-emitting devices

Lifetime and resistivity modifications induced by helium implantation in silicon: Experimental analysis with an ac profiling technique

S. Daliento, L. Mele, P. Spirito, L. Gialanella, and B. N. Limata

J. Appl. Phys. 103, 024504 (2008); http://dx.doi.org/10.1063/1.2832637 (8 pages) | Cited 1 time

Online Publication Date: 22 January 2008

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The effect of He ion bombardment on silicon based devices can be seen observing a change of their electric properties, that are relevant for their application, as well as through the modification of some local properties, in particular, resistivity and recombination lifetime, that in turn reflect the microscopic modification of their structure. The knowledge of the relation between these two aspects of the modifications induced by ion implantation would represent a powerful tool to design new devices and processes. This paper presents the results of an experimental analysis, where the modifications of the electrical properties of power devices, induced by helium implantation, were correlated to both the local recombination lifetime and the resistivity depth profile measured using a differential ac technique. Various measurements were performed for a wide range of temperatures to obtain information on the energy levels of the recombination centers which are responsible for the observed variations of the local properties of the device. The investigation was performed varying both the beam energy (from 3.5 to 5.8 MeV) and dose (1×108–5×1011 ions/cm2), providing a complete picture of the implantation effects. Finally, an application to the switching behavior of a fast recovery power diode is presented.
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81.05.Cy Elemental semiconductors
72.80.Cw Elemental semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
61.80.Jh Ion radiation effects
61.72.uf Ge and Si

Theory of a quasihomogeneous field-effect transistor

Z. S. Gribnikov, G. I. Haddad, and J. Eizenkop

J. Appl. Phys. 103, 024505 (2008); http://dx.doi.org/10.1063/1.2830714 (7 pages) | Cited 1 time

Online Publication Date: 23 January 2008

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We consider the stationary characteristics and high-frequency conductance of dual-gate field-effect transistors with a substantially inhomogeneous capacitive connection between gates and a current-conducting channel for an electron enhancement control mode. In most cases, such transistors are quasihomogeneous because their stationary JV-characteristics are not different from characteristics of perfectly homogeneous devices, which can be described by a certain effective channel length. But a nonstationary small-signal conductance of such transistors with the same stationary characteristics can be noticeably different since it is dependent on detailed space distributions of the capacitive inhomogeneity. In particular, a high-frequency gate current can depend on the stationary current direction in channels with symmetrical stationary characteristics. We discuss in detail the cases when a specific channel-gate capacitance increases or decreases monotonically along the channel current direction. Then high-frequency gate currents depend substantially on the stationary channel current direction (in spite of the same stationary JV-characteristics for both directions).
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85.30.Tv Field effect devices

Characterization of high-temperature PbTe p-n junctions prepared by thermal diffusion and by ion implantation

A. V. Butenko, R. Kahatabi, E. Mogilko, R. Strul, V. Sandomirsky, Y. Schlesinger, Z. Dashevsky, V. Kasiyan, and S. Genikhov

J. Appl. Phys. 103, 024506 (2008); http://dx.doi.org/10.1063/1.2832634 (6 pages) | Cited 5 times

Online Publication Date: 23 January 2008

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Two types of high-quality PbTe p-n junctions, prepared by thermal diffusion of In4Te3 gas [thermally diffused junction (TDJ)] and by ion implantation [implanted junction (IJ)] of indium (In-IJ) and zinc (Zn-IJ), have been characterized. Capacitance-voltage and current-voltage characteristics have been measured over a temperature range from ∼ 10 to  ∼ 180 K. The saturation current density J0 in both diode types was ∼ 10−5 A/cm2 at 80 K, while at 180 K, J0 ∼ 10−1 A/cm2 in TDJ and ∼ 1 A/cm2 in both IJ diodes. At 80 K, the reverse current started to increase markedly at a bias of ∼ 400 mV for TDJ and at ∼ 550 mV for IJ. The ideality factor was about 1.5–2 for both diode types at 80 K. Both diode types were linearly graded. The height of the junction barrier, the concentration and the concentration gradient of the impurities, and the temperature dependence of the static dielectric constant have been determined. The zero-bias resistance times area product (R0Ae) at 80 K is 850 Ω cm2 for TDJ, 250 Ω cm2 for In-IJ, and ∼ 80 Ω cm2 for Zn-IJ, while at 180 K, R0Ae ∼ 0.38 Ω cm2 for TDJ and ∼ 0.1 Ω cm2 for both IJ diodes. The estimated detectivity is D* ∼ 1011 cm Hz1/2/W at T = 80 K, determined mainly by background radiation, while at T = 180 K, D* decreases to 5×109–1010 cm Hz1/2/W and is determined by the Johnson noise.
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66.30.Xj Thermal diffusivity
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
77.22.Ch Permittivity (dielectric function)
61.72.up Other materials

The morphology control of pentacene for write-once-read-many-times memory devices

Jian Lin and Dongge Ma

J. Appl. Phys. 103, 024507 (2008); http://dx.doi.org/10.1063/1.2836793 (4 pages) | Cited 14 times

Online Publication Date: 28 January 2008

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We realized write-once-read-many-times (WORM) memory devices based on pentacene and demonstrated that the morphology control of the vacuum deposited pentacene thin film is greatly important for achieving the unique nonvolatile memory properties. The resulted memory devices show a high ON/OFF current ratio (104), long retention time (over 12 h), and good storage stability (over 240 h). The reduction of the barrier height caused by a large interface dipole and the damage of the interface dipole under a critical bias voltage have been used to explain the transition processes. The achievement of excellent WORM memory based on pentacene opens up a new application field for organic materials.
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84.30.Sk Pulse and digital circuits

Schrödinger equation Monte Carlo in two dimensions for simulation of nanoscale metal-oxide-semiconductor field effect transistors

Wanqiang Chen, Leonard F. Register, and Sanjay K. Banerjee

J. Appl. Phys. 103, 024508 (2008); http://dx.doi.org/10.1063/1.2809403 (15 pages) | Cited 4 times

Online Publication Date: 29 January 2008

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A quantum transport simulator, Schrödinger equation Monte Carlo in two dimensions (SEMC-2D), is presented that provides a rigorous yet reasonably computationally efficient quantum mechanical treatment of real scattering processes within quantum transport simulations of nanoscale metal-oxide-semiconductor field effect transistors (MOSFETs). This work represents an extension of an early version of SEMC for simulating quantum transport and scattering in quasi-one-dimensional device geometries such as encountered in conventional and quantum-cascade lasers. In many respects SEMC is simply a variation on nonequilibrium Green’s function techniques, with scattering as well as carrier injection into the simulation region treated via Monte Carlo techniques. In this regard, SEMC also represents a quantum analog of semiclassical Monte Carlo. Scattering mechanisms considered include crystal momentum randomizing acoustic and optical intra- and intervalley scattering (and intra- and intersubband scattering), and nonrandomizing surface roughness scattering. Simulation results for nanoscale dual-gate MOSFET geometries are provided that illustrate the method and the continuing need for accurate modeling of scattering even in nanoscale MOSFETs.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
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