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8 Feb 1993

Volume 62, Issue 6, pp. 541-659

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Investigation of charge trapping centers in silicon nitride films with a laser‐microwave photoconductive method

Lei Zhong and Fumio Shimura

Appl. Phys. Lett. 62, 615 (1993); http://dx.doi.org/10.1063/1.108873 (3 pages) | Cited 10 times

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A new method using a laser microwave photoconductance (LMPC) technology for the investigation of charge trapping centers in silicon nitride films was demonstrated by studying the ultraviolet (UV) irradiation effect upon minority‐carrier recombination lifetime of silicon with the film. The lifetime is found dependent on the film thickness. UV irradiation dramatically decreases the lifetime for the samples with the thick film. The decreased lifetime is transient and recovers to the initial value after long time storage at room temperature. The recovery accelerates with increasing temperature. The lifetime behavior is correlated with the charge states of K centers in the nitride film. It is then shown that the electronic structure of the charge trapping centers can be studied by an investigation of the lifetime recovery process after UV irradiation with temperature controlled LMPC measurements.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Ng Insulators

Well resolved room‐temperature photovoltage spectra of GaAs‐GaInP quantum wells and superlattices

Xiaoguang He and Manijeh Razeghi

Appl. Phys. Lett. 62, 618 (1993); http://dx.doi.org/10.1063/1.108874 (3 pages) | Cited 12 times

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We report the first well resolved room‐temperature photovoltage spectra due to the sublevel transitions in the GaInP‐GaAs superlattices and multiquantum wells grown by low pressure metalorganic chemical vapor deposition. Sharp well resolved peaks attributed to exciton absorption of the electron‐to‐light hole and electron‐to‐heavy hole have been observed at room temperature. This indicates that GaAs‐GaInP is a promising material for the application of the modulators, optical switches, and optical bistable divices. Satisfactory agreements between experimental measurements and theoretical results have been obtained. These results demonstrate that photovoltage spectroscopy is a simple, but very powerful tool to study quantum confinement structures.  
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78.66.Fd III-V semiconductors
73.50.Pz Photoconduction and photovoltaic effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Voltage‐tunable dual‐mode operation InAlAs/InGaAs quantum well Infrared photodetector for narrow‐ and broadband detection at 10 μm

Y. H. Wang, Sheng S. Li, and Pin Ho

Appl. Phys. Lett. 62, 621 (1993); http://dx.doi.org/10.1063/1.108875 (3 pages) | Cited 15 times

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A new photoconductive (PC) and photovoltaic (PV) dual‐mode operation quantum well infrared photodetector using a lattice‐matched n‐type In0.52Al0.48As/In0.53Ga0.47As system has been developed for both the narrow‐band (Δλ/λp=7%) and broadband (Δλ/λp=24%) detection with a peak spectral response around λp=10 μm. The detection scheme utilizes a voltage‐tuned bound‐to‐miniband transition from the ground state in the In0.53Ga0.47As(110 Å) quantum well to the global miniband states in the InAlAs/InGaAs superlattice barrier layers. The detectivity D∗λ for the PV mode operation was found to be 5.7×109 cm √Hz/W at λp=10 μm and T=67 K, while D∗λ for the PC mode operation was found to be 5.8×109 √Hz/W at Vb =0.5 V, λp=10.3 μm, and T=67 K.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
73.50.Pz Photoconduction and photovoltaic effects

Continuous wave operation on extremely low‐temperature (375 °C)‐grown AlGaAs quantum‐well lasers

Sei‐ichi Miyazawa, Yoshinobu Sekiguchi, Masahiro Okuda, Mitsutoshi Hasegawa, and Hidetoshi Nojiri

Appl. Phys. Lett. 62, 624 (1993); http://dx.doi.org/10.1063/1.108876 (3 pages) | Cited 1 time

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We report on the continuous wave (cw) operation of AlGaAs single‐quantum‐well (SQW) lasers grown at a low temperature (375 °C) by molecular‐beam epitaxy (MBE). The threshold current and the differential quantum efficiency of the ridge‐waveguide laser were 10 mA and 82%, respectively. During the life test, no obvious degradation was observed beyond 2300 h under 8 mW cw operation at 50 °C. The cw operation of SQW lasers grown at low temperatures was achieved by the long baking of the MBE system and the reduction of the V/III flux ratio.
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42.55.Px Semiconductor lasers; laser diodes
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Optical absorption in quantum wells with two characteristic curvatures

N. F. Johnson and J. E. Vargas

Appl. Phys. Lett. 62, 627 (1993); http://dx.doi.org/10.1063/1.109616 (3 pages) | Cited 1 time

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Novel features are predicted in the infrared absorption spectrum of an interacting electron gas in a parabolic quantum well with two characteristic curvatures (biparabolic quantum well). A series of well‐defined absorption peaks appears below the frequency of the usual center‐of‐mass absorption. These subfundamental peaks correspond to modes of the coupled electron gas and light system, and lie beyond the usual treatment of light absorption within first‐order perturbation theory.
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78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.30.Fs III-V and II-VI semiconductors

Large electric field effects in YBa2Cu3O7−δ films containing weak links

J. Mannhart, J. Ströbel, J. G. Bednorz, and Ch. Gerber

Appl. Phys. Lett. 62, 630 (1993); http://dx.doi.org/10.1063/1.108877 (3 pages) | Cited 44 times

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The influence of applied electric fields on the transport properties of weak links in YBa2Cu3O7−δ films has been investigated. It is found that the critical temperature Tc0 of epitaxial films containing weak links can be reduced by 10 K with applied electric fields of 6 MV/cm. In one case, Tc0 shifts of up to 25–30 K were observed. These are by far the largest Tc shifts reported for any superconducting system.
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74.25.N- Response to electromagnetic fields
74.50.+r Tunneling phenomena; Josephson effects
74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors

Compositional effects in YxBayCuzO7−δ thin films prepared by metalorganic chemical vapor deposition

B. Schulte, M. Maul, P. Häussler, and H. Adrian

Appl. Phys. Lett. 62, 633 (1993); http://dx.doi.org/10.1063/1.108878 (3 pages) | Cited 12 times

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We report on effects of composition onto superconducting and structural properties of Y‐Ba‐Cu‐O thin films, prepared by a carrier‐gas free metalorganic chemical vapor deposition technique. Thin films with critical temperatures Tc≥90 K, transition widths ΔTc≤1 K, and critical current densities jc (T=77 K, B=0 T)≥106 A/cm2 can be prepared by this method. Here we report on a strong dependence of the Tc on the ratio of Ba/Cu. For Ba/Cu<2 the surfaces show CuO precipitates, increasing in quantity and size with increasing concentration of Cu. An excess of Y leads to oriented inclusions of cubic Y2O3. A deficit of Y and Cu causes an expansion of the c‐lattice parameter. To investigate the influence of Y2O3 and CuO precipitates on the pinning potential, resistive transitions in magnetic fields up to 12 T were measured and interpreted by a thermal activated flux‐creep model. These measurements indicate the inefficiency of both, inclusions and precipitates, on the enhancement of the pinning potential.
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74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.25.-q Properties of superconductors
74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors

High carrier‐to‐noise ratio achieved on magneto‐optic recording disks using a plurality of magneto‐optic recording layers

C.‐J. Lin

Appl. Phys. Lett. 62, 636 (1993); http://dx.doi.org/10.1063/1.108879 (3 pages) | Cited 2 times

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Very high carrier‐to‐noise ratios of 67 dB (30 kHz bandwidth) were achieved on magneto‐optic recording disks that utilize two thin magneto‐optic layers. This improvement came primarily from the reduction in the disk writing noise. We explain this noise reduction through the statistical averaging of the written magnetic transition positions in these two active layers. In principle the disk writing noise can be further reduced when more active layers are utilized in the disk structure.
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85.70.Sq Magnetooptical devices
75.70.-i Magnetic properties of thin films, surfaces, and interfaces
78.66.-w Optical properties of specific thin films

Epitaxial PtFe(001) thin films on MgO(001) with perpendicular magnetic anisotropy

B. M. Lairson, M. R. Visokay, R. Sinclair, and B. M. Clemens

Appl. Phys. Lett. 62, 639 (1993); http://dx.doi.org/10.1063/1.108880 (3 pages) | Cited 93 times

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We report a technique for producing the ordered PtFe intermetallic compound with perpendicular magnetic anisotropy and a preferred c‐axis orientation perpendicular to the film plane. PtFe alloys possess high magneto‐optic Kerr rotations and magnetizations, suggesting them as likely candidates for magneto‐optic and perpendicular magnetic recording.
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75.30.Gw Magnetic anisotropy
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Bb Fe and its alloys

Steplike behavior of photoluminescence peak energy and formation of p‐type porous silicon

Shu‐Lin Zhang, Kuok‐san Ho, Yongtian Hou, Bidong Qian, Peng Diao, and Shengmin Cai

Appl. Phys. Lett. 62, 642 (1993); http://dx.doi.org/10.1063/1.108881 (3 pages) | Cited 13 times

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The photoluminescence spectra from a series of porous silicon samples formed in HF concentrations at constant current density and fixed forming times, are presented. A novel steplike behavior of photoluminescence peak energy was observed. A formation mechanism based on the quantum confinement of porous Si walls has been proposed to explain the experimental results.
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78.55.Hx Other solid inorganic materials
81.65.-b Surface treatments
82.45.-h Electrochemistry and electrophoresis

Longitudinal expansion of space‐charge dominated drifting beam bunches with a parabolic line charge density distribution

J. G. Wang, D. X. Wang, and M. Reiser

Appl. Phys. Lett. 62, 645 (1993); http://dx.doi.org/10.1063/1.108882 (3 pages) | Cited 2 times

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An experiment was performed for the first time to demonstrate linear longitudinal space‐charge forces on drifting electron beam bunches with a parabolic line charge density distribution. The parabolic electron beam bunch was produced by a gridded electron gun and guided into a short transport channel consisting of an induction acceleration module and three matching lenses. The time‐resolved beam energy was measured at the end of the channel by both a retarding field energy analyzer and a deflecting field energy analyzer. The experimental results were compared with theory and good agreement was found.
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29.27.Bd Beam dynamics; collective effects and instabilities
29.27.Fh Beam characteristics
41.85.Ja Particle beam transport
41.85.Ew Particle beam profile, beam intensity

Memory effect of an organic photoconductor and its application to a neuron model

Akiteru Fujii, Mitsuru Yoneyama, Kei Ishihara, Shuichi Maeda, and Tetsuo Murayama

Appl. Phys. Lett. 62, 648 (1993); http://dx.doi.org/10.1063/1.108883 (3 pages) | Cited 6 times

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A new type of organic photoconductor composed of 9‐ethylcarbazole‐3‐carbaldehyde diphenylhydrazone (DPH) dispersed in a polycarbonate polymer (PCR) film, when in the presence of thio‐Michler’s ketone (TMK), was found to exhibit a sustained state of enhanced conductivity following visible irradiation. At room temperature, the enhanced current is observed to decay slowly over a period of a day and when heated it rapidly returns to its original state. A potential application of this ‘‘memory’’ effect to an artificial neuron model, using such memory‐type organic photoconductors as optically controllable interconnections, is discussed. A liquid‐crystal cell is used to demonstrate a nonlinear‐saturated response dependent on a weighted input electric signal.
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73.50.Pz Photoconduction and photovoltaic effects
73.61.Ph Polymers; organic compounds
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks

Switching characteristics of multi‐ion‐beam reactive sputter deposited Pb(Zr,Ti)O3 thin films

H. Hu and S. B. Krupanidhi

Appl. Phys. Lett. 62, 651 (1993); http://dx.doi.org/10.1063/1.108886 (3 pages) | Cited 2 times

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The switching of the multi‐ion‐beam reactive sputter deposited Pb(Zr0.5,Ti0.5)O3 thin films has been characterized by using several parameters such as switching time (ts), switched charge density (Qs), nonswitched charge density (Qns), and activation field (α). Comparison was made between films grown with and without low‐energy oxygen ion bombardment. It was found that while there is not much difference in ts between the two kinds of films, the bombarded films show higher Qs/Qns, lower ts/Qs, and lower α. These results are consistent with previous results on the remanent polarization (Pr) and coercive field (Ec) and indicate that the bombardment has induced changes towards facilitating the domain reversal in the films.
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77.80.Fm Switching phenomena
81.15.Cd Deposition by sputtering

Adhesion studies of Cu‐Cr alloys on Al2O3

Chin‐Jong Chan, Chin‐An Chang, Curtis E. Farrell, and Alex G. Schrott

Appl. Phys. Lett. 62, 654 (1993); http://dx.doi.org/10.1063/1.108888 (3 pages) | Cited 10 times

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Adhesion of Cu‐Cr alloys to c‐axis sapphire wafers has been studied. A large increase in peel strength was observed when the Cr content exceeded 15 at. % for the as‐deposited alloy films. The high measured peel strength can be attributed to Cr that segregates to the sapphire‐alloy interface due to its high free energy in the metastable alloy structure. Heat treatment was found to greatly enhance the adhesion of low Cr containing (15 at. %) Cu‐Cr alloys to c‐axis sapphire. Cr was found to segregate to the sapphire‐alloy interface or separate as spherical precipitates in the Cu matrix upon appropriate thermal treatment. Increase in peel strength between sapphire and the low Cr alloy interface was observed at annealing temperatures as low as 200 °C.
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68.35.Gy Mechanical properties; surface strains
68.08.Bc Wetting
68.35.Fx Diffusion; interface formation

Catalytic growth of carbon microtubules with fullerene structure

M. José‐Yacamán, M. Miki‐Yoshida, L. Rendón, and J. G. Santiesteban

Appl. Phys. Lett. 62, 657 (1993); http://dx.doi.org/10.1063/1.108857 (3 pages) | Cited 105 times

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A method to grow carbon microtubules with fullerene structure (buckytubes) has been identified. The method consists of the catalytic decomposition of acetylene over iron particles at 700 °C. Carbon microtubules of up to 50 μm in length are synthesized by this method. Electron diffraction and high resolution electron microscopy studies demonstrate that the structure of these microtubules corresponds to the helical structure recently reported by S. Iijima, Nature 354, 56(1991), prepared using an arc‐discharge evaporation method.
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81.10.-h Methods of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation
61.66.Bi Elemental solids
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