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15 Mar 2000

Volume 87, Issue 6, pp. 2673-3189

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Effect of ion induced damage on carrier lifetimes in strained CdZnSe/ZnSe quantum wells

L. M. Sparing, A. M. Mintairov, J. H. Hodak, I. B. Martini, G. V. Hartland, U. Bindley, S. Lee, J. K. Furdyna, J. L. Merz, and G. L. Snider

J. Appl. Phys. 87, 3063 (2000); http://dx.doi.org/10.1063/1.372300 (5 pages) | Cited 2 times

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Studies of the effects of reactive ion etching on molecular beam epitaxy grown CdxZn1−xSe/ZnSe strained quantum wells (QWs) using photoluminescence (PL) and time-resolved reflectivity measurements are reported. The shallow (50 nm cap layer) QW samples exhibit a blueshift in their PL peak position as a function of etch voltage up to a certain point, after which the blueshift is reduced. The reduction in the blueshift of the PL spectrum is strongly correlated with a reduction in the carrier lifetimes measured by transient reflectivity. From these experiments we suggest that the initial blueshift is a result of ion damage at the surface interacting with strain in the QW. On the other hand, the reduced carrier lifetime at higher voltages is a result of more severe structural damage in the QW. © 2000 American Institute of Physics.
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73.61.Ga II-VI semiconductors
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.47.-p Spectroscopy of solid state dynamics

Micromagnetic studies of read and write process in magnetoresistive random access memory

Dan Wei, C. K. Ong, and Zheng Yang

J. Appl. Phys. 87, 3068 (2000); http://dx.doi.org/10.1063/1.372301 (6 pages) | Cited 3 times

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A micromagnetic model is established to analyze the read and write processes in a magnetoresistance random access memories (MRAM) cell. The magnetoresistive curves of NiFeCo/interlayer/NiFeCo cells are analyzed and compared with available experiments. The switching fields of the two magnetic layers A and B in a MRAM cell are studied versus different geometrical parameters of a cell. The word current IwA and IwB corresponding, respectively, to the switching of films A and B, and the related error of IwA and IwB under a given sense current Is, are analyzed and compared with experiment. In a cell with a given width W, proper geometrical parameters such as the thickness of the magnetic layers and the aspect ratio (length over width) are found based on the analysis of the IwA−Is and IwB−Is curves. © 2000 American Institute of Physics.
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85.70.Ay Magnetic device characterization, design, and modeling
84.30.Sk Pulse and digital circuits
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.50.Bb Fe and its alloys
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

Regional approximation approach to space charge limited tunneling injection in polymeric devices

M. Koehler and I. A. Hümmelgen

J. Appl. Phys. 87, 3074 (2000); http://dx.doi.org/10.1063/1.372302 (6 pages) | Cited 9 times

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We developed a theory that explains the charge injection and transport in conjugated polymer films such as those used in organic light emitting diodes. Using the regional approximation the effect of the space charge on the current density of electrons tunneling from metal electrodes to the lowest unoccupied molecular orbital of a polymer film is calculated. The space charge is considered to decrease with increasing distance of the injecting electrode. If the space charge occupies only a limited region between the tunneling distance and the collecting electrode , the current (I) is found to depend on a power law of the applied voltage (V). However, if the space charge occupies all the region between the tunneling distance and the collecting electrode, I is found to vary exponentially on V for lower V values and follow approximately the law of Child at high V. The space charge limited tunneling current (SCTC) theory gives the same results of the space charge limited conduction theory when the energy barrier for charge carrier injection is small or when the polymer layer is thick. The SCTC theory is compared to the experimental data. It is shown that there is a good agreement between theory and experiment, concerning both current magnitude and current versus voltage dependence. © 2000 American Institute of Physics.
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72.20.Ht High-field and nonlinear effects
73.50.Fq High-field and nonlinear effects
78.66.Qn Polymers; organic compounds
73.40.Gk Tunneling
72.15.Nj Collective modes (e.g., in one-dimensional conductors)

Semitransparent cathodes for organic light emitting devices

P. E. Burrows, G. Gu, S. R. Forrest, E. P. Vicenzi, and T. X. Zhou

J. Appl. Phys. 87, 3080 (2000); http://dx.doi.org/10.1063/1.372303 (6 pages) | Cited 63 times

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We optimize transparent organic light emitting devices (TOLEDs) using compound cathodes consisting of a thermally evaporated metal contact layer capped with indium–tin–oxide (ITO). The ITO is sputtered at rates of up to 1.6 Å/s using a high power radio frequency magnetron process. With a Mg:Ag contact layer, we demonstrate a TOLED with 50% transparency and an operating voltage within 0.3 V of a device with identical organic layers and a conventional Mg:Ag cathode. The operational lifetime of the TOLED is shown to be equal to that of a similar, nontransparent device. We also study the effects of using different contact metals, including Ca, Al and LiF, on the operating characteristics of the TOLEDs. With a thin Ca contact layer, undoped TOLEDs with >80% peak transparency operating at (5.9±0.1) V at a brightness of >100 cd/m2 are demonstrated. These devices have application to transparent, head-up displays and to full color, stacked organic light emitting devices. © 2000 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.66.Qn Polymers; organic compounds
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Comparison of nonlinear and nonstationary response of conventional and resonant cavity enhanced p-i-n photodiode

Petar S. Matavulj, Dušan S. Golubović, and Jovan B. Radunović

J. Appl. Phys. 87, 3086 (2000); http://dx.doi.org/10.1063/1.372304 (7 pages)

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High-power illumination of a p-i-n photodiode results in nonlinear operating conditions and, of course, in nonlinear electric response. This article presents an investigation and comparison of the nonlinear response of conventional and resonant cavity enhanced (RCE) p-i-n photodiodes constructed using a two-valley semiconductor (GaAs). The presented results are obtained through numerical simulation of the complete phenomenological model for a two-valley semiconductor in the submicron region for several bias voltages and several values of Dirac pulse optical powers. The nonlinear behavior is analyzed through carrier transit and response time. Nonstationary effects exist in two-valley semiconductors in the presence of adequate perturbation of the electric field in the absorption layer. The present investigation shows that the RCE p-i-n photodiode reaches the nonlinear operating regime for smaller incident optical irradiances. © 2000 American Institute of Physics.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.30.De Semiconductor-device characterization, design, and modeling
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