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30 Mar 1998

Volume 72, Issue 13, pp. 1527-1658

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High-power, continuous-wave, singly resonant, intracavity optical parametric oscillator

T. J. Edwards, G. A. Turnbull, M. H. Dunn, M. Ebrahimzadeh, and F. G. Colville

Appl. Phys. Lett. 72, 1527 (1998); http://dx.doi.org/10.1063/1.120572 (3 pages) | Cited 14 times

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A high-power continuous-wave optical parametric oscillator based on the nonlinear material KTiOAsO4 and pumped internal to a tunable Ti:sapphire laser is described. The use of the intracavity pumping approach has enabled operation of a singly resonant oscillator (SRO), resulting in the generation of as much as 1.46 W of infrared power in a 11.5-mm-long crystal. Amplitude-stable signal and idler outputs, each in excess of 500 mW, over the respective wavelength ranges of 1.11–1.20 and 2.44–2.86 μm have been extracted from the SRO. We demonstrate up to 90% down-conversion of the optimum Ti:sapphire output power to the SRO, confirming our recent theoretical predictions. The performance characteristics of the device demonstrate that practical, stable, and efficient operation of continuous-wave SROs at watt-level output power can be readily achieved in conventional birefringent materials by exploiting the intracavity pumping approach. © 1998 American Institute of Physics.
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42.65.Yj Optical parametric oscillators and amplifiers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.60.Pk Continuous operation
42.70.Mp Nonlinear optical crystals
42.60.Fc Modulation, tuning, and mode locking

Optical modes within III-nitride multiple quantum well microdisk cavities

R. A. Mair, K. C. Zeng, J. Y. Lin, H. X. Jiang, B. Zhang, L. Dai, A. Botchkarev, W. Kim, H. Morkoç, and M. A. Khan

Appl. Phys. Lett. 72, 1530 (1998); http://dx.doi.org/10.1063/1.120573 (3 pages) | Cited 35 times

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Optical resonance modes have been observed in optically pumped microdisk cavities fabricated from 50 Å/50 Å GaN/AlxGa1−xN(x ∼ 0.07) and 45 Å/45 Å InxGa1−xN/GaN(x ∼ 0.15) multiple quantum well structures. Microdisks, approximately 9 μm in diameter and regularly spaced every 50 μm, were formed by an ion beam etch process. Individual disks were pumped at 300 and 10 K with 290 nm laser pulses focused to a spot size much smaller than the disk diameter. Optical modes corresponding to (i) the radial mode type with a spacing of 49–51 meV (both TE and TM) and (ii) the Whispering Gallery mode with a spacing of 15–16 meV were observed in the GaN microdisk cavities. The spacings of these modes are consistent with those expected for modes within a resonant cavity of cylindrical symmetry, refractive index, and dimensions of the microdisks under investigation. The GaN-based microdisk cavity is compared with its GaAs counterpart and implications regarding future GaN-based microdisk lasers are discussed. © 1998 American Institute of Physics.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Sa Microcavity and microdisk lasers
78.66.Fd III-V semiconductors
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.05.Ea III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Influence of humidity on refractive index of polymers for optical waveguide and its temperature dependence

Toshio Watanabe, Naoki Ooba, Yasuhiro Hida, and Makoto Hikita

Appl. Phys. Lett. 72, 1533 (1998); http://dx.doi.org/10.1063/1.120574 (3 pages) | Cited 16 times

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Humidity dependence of the refractive index of deuterated polymethylmethacylate (d-PMMA) is examined at a wavelength of 1.3 μm using the return loss method. The refractive index of d-PMMA increases as humidity increases at room temperature, while it decreases as humidity increases at temperatures higher than 60 °C. This humidity dependence was ascribed to the counterbalance between moisture sorption and swelling. Some hydrophobic polymers, such as silicone resin and fluorinated epoxy resin were affected by humidity to a lesser degree than d-PMMA. © 1998 American Institute of Physics.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.Jk Polymers and organics
42.79.Gn Optical waveguides and couplers
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Semiconducting polymer distributed feedback lasers

M. D. McGehee, M. A. Díaz-García, F. Hide, R. Gupta, E. K. Miller, D. Moses, and A. J. Heeger

Appl. Phys. Lett. 72, 1536 (1998); http://dx.doi.org/10.1063/1.121679 (3 pages) | Cited 136 times

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We have fabricated photopumped distributed feedback lasers by spin-casting thin films of the semiconducting polymer poly(2-butyl,5-(2′-ethyl-hexyl)-1,4-phenylenevinylene) over gratings in silicon oxide. The lasers have two modes that each have a linewidth of 0.2 nm. The lasing wavelength was tuned from 540 to 583 nm by adjusting the period of the gratings. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.79.Dj Gratings
42.60.Fc Modulation, tuning, and mode locking

Characterization of AlGaInN diode lasers with mirrors from chemically assisted ion beam etching

M. Kneissl, D. P. Bour, N. M. Johnson, L. T. Romano, B. S. Krusor, R. Donaldson, J. Walker, and C. Dunnrowicz

Appl. Phys. Lett. 72, 1539 (1998); http://dx.doi.org/10.1063/1.120575 (3 pages) | Cited 47 times

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Current-injection InGaAlN heterostructure laser diodes grown by metalorganic chemical vapor deposition on sapphire substrates are demonstrated with mirrors fabricated by chemically assisted ion beam etching. Due to the independent control of physical and chemical etching, smooth vertical sidewalls with a root-mean-squared roughness of 4–6 nm have been achieved. The diodes lased under pulsed current-injection conditions at wavelengths in the range from 419 to 423 nm. The lowest threshold current density was 25 kA/cm2. Lasing was observed in both gain-guided and ridge-waveguide test diodes, with cavity lengths from 300 to 1000 μm; and output powers of 10–20 mW were achieved. Laser performance is illustrated with light output-current and current–voltage characteristics and with a high-resolution optical spectrum.© 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.79.Bh Lenses, prisms and mirrors
81.65.Cf Surface cleaning, etching, patterning
42.86.+b Optical workshop techniques

An efficient all-solid-state ultraviolet laser source

A. H. Kung, Lee Jr-i, and Poe-Jou Chen

Appl. Phys. Lett. 72, 1542 (1998); http://dx.doi.org/10.1063/1.120576 (3 pages)

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Stable high-power operation in the uv is achieved from a commercial multi-kHz diode-pumped multimode Q-switched Nd:YAG laser by fourth-harmonic generation in an external cavity. Over 640 mW at 266 nm in a TEM00 beam and an internal conversion efficiency of 30% were obtained. A lifetime of one-billion shots at several hundred mW and a long-term power stability of ±1% were recorded, demonstrating that this source has the potential of stable long-term operation using readily available components. © 1998 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Sub-pJ operation of broadband asymmetric Fabry–Perot all-optical gate with coupled cavity structure

Tomoyuki Akiyama, Masahiro Tsuchiya, and Takeshi Kamiya

Appl. Phys. Lett. 72, 1545 (1998); http://dx.doi.org/10.1063/1.120577 (3 pages) | Cited 6 times

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We report on all-optical gating characteristics of a novel low-temperature-grown asymmetric Fabry–Perot (AFP) device, in which improvement of performance with respect to conventional AFP all-optical switches is achieved by a short and coupled cavity configuration. Sub-pJ ( ∼ 800 fJ) operation is realized with a high contrast ratio (>10 dB) over a broad wavelength range (∼7 nm). Even for 250 fJ pump pulses, a contrast ratio of >6 dB is obtained over a 4 nm wavelength range. © 1998 American Institute of Physics.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.79.-e Optical elements, devices, and systems

Room-temperature persistent spectral hole burning in Sm-doped KLaF4 crystals

Nobuhiro Kodama, Tomoko Takahashi, and Kazuyuki Hirao

Appl. Phys. Lett. 72, 1548 (1998); http://dx.doi.org/10.1063/1.120578 (2 pages) | Cited 1 time

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Persistent spectral hole burning is observed at room temperature in the excitation spectrum for the 7F0→5D0 transition of Sm2+ in KLaF4 single crystals. The hole width and depth are about 10 cm−1 and 18% of the total intensity, respectively. It is concluded that the dominant burning mechanism in this crystal is a photoionization of electron trapping at a site other than Sm3+ ions because of the absence of an antihole around the burned hole. © 1998 American Institute of Physics.
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42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency

Si/SiGe resonant-cavity photodiodes for optical storage applications

M. Seto, W. B. de Boer, V. S. Sinnis, A. P. Morrison, W. Hoekstra, and S. de Jager

Appl. Phys. Lett. 72, 1550 (1998); http://dx.doi.org/10.1063/1.121111 (3 pages) | Cited 2 times

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We report on a resonant cavity photodiode with a Si/SiGe Bragg mirror grown by low temperature chemical vapor deposition suitable for short wavelength detection around 600–700 nm. The presence of Fabry-Pérot oscillations in the spectral response of the photodiode are indicative of its wavelength selectivity. © 1998 American Institute of Physics.
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85.60.Dw Photodiodes; phototransistors; photoresistors
42.79.Vb Optical storage systems, optical disks
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.79.Bh Lenses, prisms and mirrors

Differential gain and threshold current of 1.3 μm tensile-strained InGaAsP multi quantum well buried-heterostructure lasers grown by metalorganic molecular beam epitaxial growth

Masayuki Itoh, Hideo Sugiura, Hiroshi Yasaka, Yasuhiro Kondo, Kenji Kishi, Mitsuo Fukuda, and Yoshio Itaya

Appl. Phys. Lett. 72, 1553 (1998); http://dx.doi.org/10.1063/1.121112 (3 pages) | Cited 3 times

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The laser characteristics of 1.3 μm tensile-strained InGaAsP/InP multi quantum well (MQW) lasers were studied. The tensile strain of well layers ranged from 0.5% to 1.8%. The level of the strain dependence of the threshold current shows that the threshold current decreases drastically with increase in the tensile strain from 0.5% to 1.3%, while it stays almost constant in the 1.45%–1.8% range. Among all the samples, the 1.3% tensile-strained MQW laser shows superior performance in terms of minimum threshold current and maximum differential gain (∂g/∂N). The 1.3% tensile strain is the optimum level for the tensile-strained MQW buried-heterostructure lasers. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

A fiber laser for effective generation of tunable single- and dual-wavelength mode-locked optical pulses

Y. Zhao and C. Shu

Appl. Phys. Lett. 72, 1556 (1998); http://dx.doi.org/10.1063/1.121113 (3 pages) | Cited 8 times

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A scheme to produce wavelength-tunable pulses with gigahertz bit rate is demonstrated by active mode locking of a fiber laser. Fiber gratings are used in the setup to play the simultaneous roles of wavelength selective mirrors, tunable optical filters, and output fiber couplers. Single- and dual-wavelength picosecond pulses are generated with a flexibility of switching between the outputs by polarization adjustment. A strain tuning process is successfully developed and a total operating range of 13.62 nm towards both shorter and longer wavelengths is demonstrated. Our experimental observations are in good agreement with the calculated results. © 1998 American Institute of Physics.
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42.55.Wd Fiber lasers
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.Dj Gratings
42.79.Bh Lenses, prisms and mirrors
42.79.Ci Filters, zone plates, and polarizers
42.81.Qb Fiber waveguides, couplers, and arrays

Polymeric wavelength filters with polymer gratings

Min-Cheol Oh, Myung-Hyun Lee, Joo-Heon Ahn, Hyung-Jong Lee, and Seon Gyu Han

Appl. Phys. Lett. 72, 1559 (1998); http://dx.doi.org/10.1063/1.121114 (3 pages) | Cited 33 times

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Wavelength filters with Bragg gratings are demonstrated based on low-loss polymer waveguides and high-refractive-index polymer gratings. Two kinds of fluorinated polymers, perfluorocyclobutane and fluorinated poly(arylene ethers) are used for the low-loss waveguide operating around the 1.55 μm wavelength. The polymer grating is made of Resole, and it is successfully integrated in the polymer waveguides. In order to fabricate the Bragg gratings on the polymer waveguides, we use a phase mask and a Hg lamp in a mask aligner as the illuminating source instead of the laser. This method provides uniform gratings on a large area as well as the alignment capability. In the fabricated wavelength filters, the reflectivity at the Bragg wavelength is 30 dB, the 3 dB bandwidth is as narrow as 0.6 nm, and the insertion loss is 3.7 dB. © 1998 American Institute of Physics.
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42.79.Ci Filters, zone plates, and polarizers
42.70.Jk Polymers and organics
42.79.Dj Gratings
42.79.Gn Optical waveguides and couplers

Temporal solitary subpicosecond pulse propagation in a dye-doped polymer slab waveguide with a negative nonlinear refractive index

Shiro Yamakawa, Keigo Hamashima, Takeshi Kinoshita, and Keisuke Sasaki

Appl. Phys. Lett. 72, 1562 (1998); http://dx.doi.org/10.1063/1.121115 (3 pages) | Cited 5 times

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Subpicosecond (150 fs) temporal solitary pulse propagation is observed in an azo-dye-Disperse Red 1 doped (DR1) polymer waveguide. The negative nonlinear refractive index enables the generation of bright soliton in the medium with positive group velocity dispersion. Moreover, the pulse narrowing up to 97 fs based on the high-order soliton is observed. The magnitude of the nonlinear refractive index of the DR1-doped PMMA (poly[methyl methacrylate] film is estimated by cross-correlation measurement and the assumption-free pulse-form retrieval technique.© 1998 American Institute of Physics.
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42.70.Jk Polymers and organics
42.81.Dp Propagation, scattering, and losses; solitons
42.81.Qb Fiber waveguides, couplers, and arrays
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.65.Tg Optical solitons; nonlinear guided waves

1.3 μm InGaAsP/InP lasers on GaAs substrate fabricated by the surface activated wafer bonding method at room temperature

TaekRyong Chung, Naoe Hosoda, Tadatomo Suga, and Hideki Takagi

Appl. Phys. Lett. 72, 1565 (1998); http://dx.doi.org/10.1063/1.121116 (2 pages) | Cited 20 times

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InGaAsP/InP strained-layer quantum well ridge waveguide lasers of 1.3 μm have been successfully bonded to a GaAs substrate by surface activated wafer direct bonding at room temperature. In this method, the surfaces of two wafers are activated by Ar fast atom beam irradiation and joined under high vacuum conditions. In most cases a high bonding strength was attained. No microcracks and voids were observed by transmission electron microscopy at the bonded interface. A low threshold current density of about 500 A/cm2 has been achieved. This technique is very promising to realize monolithic integration of optoelectronic integrated circuits for optical communication and interconnections. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
81.05.Ea III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
68.35.Gy Mechanical properties; surface strains
42.86.+b Optical workshop techniques
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Acoustic time reversal with mode conversion at a solid-fluid interface

Carsten Draeger, Didier Cassereau, and Mathias Fink

Appl. Phys. Lett. 72, 1567 (1998); http://dx.doi.org/10.1063/1.121117 (3 pages) | Cited 8 times

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Acoustic time-reversal experiments are mostly carried out in fluid media. This letter presents experiments proving the capability of a time-reversal mirror to obtain simultaneous focusing of both propagation modes inside a solid. The mirror is located in a surrounding fluid and records the longitudinal and transverse wavefronts (created by a laser impact on the solid) after conversion into pressure waves at the solid-fluid interface. We show that the time-reversed pressure wavefronts are reconverted mostly to their original propagation mode and focus simultaneously at the location of the laser impact. © 1998 American Institute of Physics.
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62.65.+k Acoustical properties of solids
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
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Fractional dissociation efficiency measurements of D2 in a helical resonator D2–N2 gas mixture discharge

B. N. Ganguly and P. Bletzinger

Appl. Phys. Lett. 72, 1570 (1998); http://dx.doi.org/10.1063/1.121145 (2 pages) | Cited 2 times

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Very high fractional dissociation efficiency of D2 has been measured in an inductive-mode helical resonator discharge in a % D2–% N2 gas mixture at 1 Torr pressure. For high N2 dilution, nearly 100% D2 dissociation is obtained compared to 13% for pure D2 at a constant power. The high D2 dissociation efficiency appears to be achieved through the multiquantum vibrational energy transfer from N2 to D2 populating the dissociative D2 (b 3Σu+) state at a large internuclear distance.
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82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
52.80.-s Electric discharges
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
34.50.Ez Rotational and vibrational energy transfer
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In situ growth of highly oriented Pb(Zr0.5Ti0.5)O3 thin films by low-temperature metal–organic chemical vapor deposition

G.-R. Bai, I-Fei Tsu, A. Wang, C. M. Foster, C. E. Murray, and V. P. Dravid

Appl. Phys. Lett. 72, 1572 (1998); http://dx.doi.org/10.1063/1.121118 (3 pages) | Cited 20 times

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Highly oriented, polycrystalline Pb(Zr0.5Ti0.5)O3 (PZT) thin films were successfully grown on RuO2/SiO2/(001)Si using metal–organic chemical vapor deposition (MOCVD) at 525 °C. The orientation of the PZT film was controlled by using MOCVD-deposited highly textured RuO2 bottom electrodes. A (001)-oriented PZT film was observed for growth on (101)-textured RuO2. In contrast, for (110) RuO2, the growth of (001) PZT was greatly suppressed while the growth of both (110) and (111) were enhanced, resulting in a poorly (001)-textured polycrystalline film. The as-grown PZT films exhibited a dense columnar microstructure with an average grain size of 150–250 nm. Both PZT films showed excellent ferroelectric properties without any postgrowth annealing. The (001) highly oriented PZT films showed significantly higher values of remnant polarization (Pr = 49.7 μC/cm2) and saturation polarization (Ps = 82.5 μC/cm2). In comparison, for the PZT films grown on (110) RuO2, Pr and Ps were 21.5 and 35.4 μC/cm2, respectively. © 1998 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
68.55.-a Thin film structure and morphology
77.22.Ej Polarization and depolarization

Atom-resolved electronic spectra for Alq3 from theory and experiment

A. Curioni, W. Andreoni, R. Treusch, F. J. Himpsel, E. Haskal, P. Seidler, C. Heske, S. Kakar, T. van Buuren, and L. J. Terminello

Appl. Phys. Lett. 72, 1575 (1998); http://dx.doi.org/10.1063/1.121119 (3 pages) | Cited 8 times

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The electronic structure of Alq3 is investigated using density functional theory-based calculations, photoemission and near-edge x-ray absorption fine structure. The distinct features of the observed spectra are understood in terms of contributions from the different atoms and molecular orbitals. Fingerprints of the molecular bonding and of the individual atoms are identified. These results are meant to be a reference for the monitoring of chemical processes that Alq3 may undergo during fabrication or degradation of light-emitting devices, and for the understanding of the effects of ligand or metal substitution. © 1998 American Institute of Physics.
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71.20.Rv Polymers and organic compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
79.60.Fr Polymers; organic compounds
78.70.Dm X-ray absorption spectra

Atomistic studies of segregation and diffusion in Al-Cu grain boundaries

X.-Y. Liu, Wei Xu, S. M. Foiles, and J. B. Adams

Appl. Phys. Lett. 72, 1578 (1998); http://dx.doi.org/10.1063/1.121120 (3 pages) | Cited 24 times

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The segregation of Cu atoms at Al [110] Σ11 and [001] Σ5 tilt grain boundaries was studied. Cu atoms were found to segregate to asymmetric sites at the Σ11 boundary and form zig-zag planar aggregates at the interface. Segregation is dominated by atomic size and local hydrostatic stress. Cu atoms prefer to occupy the prime diffusion path sites at both grain boundaries. Cu segregation raises the vacancy formation and diffusion activation energies at Σ11 grain boundaries, thus slowing the rate of atomic diffusion. © 1998 American Institute of Physics.
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61.72.Mm Grain and twin boundaries
66.30.Lw Diffusion of other defects
64.75.-g Phase equilibria
61.72.J- Point defects and defect clusters

Characteristics of scanning-probe lithography with a current-controlled exposure system

Masayoshi Ishibashi, Seiji Heike, Hiroshi Kajiyama, Yasuo Wada, and Tomihiro Hashizume

Appl. Phys. Lett. 72, 1581 (1998); http://dx.doi.org/10.1063/1.121121 (3 pages) | Cited 18 times

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Characteristics of atomic force microscopy lithography using a current-controlled exposure feedback system are investigated by fabricating line-and-space patterns on the negative-type electron beam resist RD2100N. We find that the cross-sectional shape of the developed resist pattern depends on the amount of exposure. The resolution depends on the resist thickness,and a minimum line width of 27 nm is obtained for a 15-nm-thick resist. The proximity effect is evaluated by comparing a resist pattern with a model calculation. Electric-field mapping inside the resist is calculated,and an exposure mechanism is proposed to explain the characteristics. © 1998 American Institute of Physics.
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85.40.Hp Lithography, masks and pattern transfer
07.79.Lh Atomic force microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
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High-current-density ITOx/NiOx thin-film diodes

W. Y. Lee, D. Mauri, and C. Hwang

Appl. Phys. Lett. 72, 1584 (1998); http://dx.doi.org/10.1063/1.121122 (3 pages) | Cited 6 times

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Thin-film diodes 0.2–4×10−5 cm2 in size were fabricated on Al2O3–TiC ceramic substrates from junctions between p-type NiOx and n-type ITOx thin films sputter deposited at ambient temperature. These diodes show a room-temperature turn-on voltage of 0.3–0.6 V and a dc forward current density exceeding 104 A/cm2 at an applied voltage of ≃ 1.5 V. The current–voltage (I–V) and capacitance–voltage (C–V) characteristics of these diodes can be described by an exponential dependence of I on the applied V and by a linear I/C2 dependence on the reverse applied V, respectively, consistent with those predicted by the various models proposed for the mechanisms for charge-carrier transport in abrupt anisotype heterojunctions. The ideality factor at low-applied V ( ⩽ 0.3 V), the junction built-in potential, and the carrier concentration deduced from these I–V and C–V data are ≃ 1.5–2, 0.20–0.24 V, and 1.90–1.97×1018/cm3, respectively. © 1998 American Institute of Physics.
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85.30.Kk Junction diodes
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Band discontinuity in strained In(As,P)/InP heterostructures

C. Monier, M. F. Vilela, I. Serdiukova, and A. Freundlich

Appl. Phys. Lett. 72, 1587 (1998); http://dx.doi.org/10.1063/1.121123 (3 pages) | Cited 17 times

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Photocurrent and photoluminescence measurements have been performed on strained InAsxP1−x/InP multiquantum wells grown by chemical beam epitaxy, for arsenic content 0.25<x<0.65 and various well widths. The energies deduced from photocurrent spectra of well-resolved electron–heavy-hole and electron–light-hole fundamental excitonic transitions are compared with calculations within the envelope function formalism including strain effects. A conduction-band offset ratio QC of 0.70±0.02 is determined and is found to be independent of the arsenic composition in wells. © 1998 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
78.55.Cr III-V semiconductors
73.50.Pz Photoconduction and photovoltaic effects

Ballistic-electron-emission microscopy and spectroscopy of metal/GaN interfaces

L. D. Bell, R. P. Smith, B. T. McDermott, E. R. Gertner, R. Pittman, R. L. Pierson, and G. J. Sullivan

Appl. Phys. Lett. 72, 1590 (1998); http://dx.doi.org/10.1063/1.121124 (3 pages) | Cited 2 times

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Ballistic-electron-emission microscopy (BEEM) spectroscopy and imaging have been applied to the Au/GaN interface. In contrast to previous BEEM measurements, spectra yield a Schottky barrier height of 1.04 eV that agrees well with the highest values measured by conventional methods. A second threshold is observed in the spectra at about 0.2 V above the first threshold. Imaging of the Au/GaN interface reveals transmission in nearly all areas, although the magnitude is small and varies by an order of magnitude. BEEM of other GaN material shows no transmission in any areas. © 1998 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

Energy level alignment at Alq/metal interfaces

S. T. Lee, X. Y. Hou, M. G. Mason, and C. W. Tang

Appl. Phys. Lett. 72, 1593 (1998); http://dx.doi.org/10.1063/1.121125 (3 pages) | Cited 104 times

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The energy level alignment for both Mg/8-hydroxyquinoline aluminum (Alq) and Au/Alq interfaces has been determined by the ultraviolet photoemission measurements. For both interfaces, the difference between the Fermi level and the low-energy edge of the highest occupied molecular orbital (HOMO) is around 1.7 eV. This implies that the Fermi level with respect to the HOMO edge of Alq is independent of the work function of Mg and Au despite a large difference in the metal work function. A Fermi level alignment model is proposed, invoking a charge transfer between the metal and Alq and the formation of a dipolar layer at the metal/Alq interface. © 1998 American Institute of Physics.
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79.60.Jv Interfaces; heterostructures; nanostructures
73.20.At Surface states, band structure, electron density of states
73.40.Ns Metal-nonmetal contacts

GaAs/AlGaAs quantum well photodetectors with a cutoff wavelength at 28 μm

A. G. U. Perera, W. Z. Shen, S. G. Matsik, H. C. Liu, M. Buchanan, and W. J. Schaff

Appl. Phys. Lett. 72, 1596 (1998); http://dx.doi.org/10.1063/1.121126 (3 pages) | Cited 15 times

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We demonstrate the longest (λc=28.6 μm) far-infrared quantum well photodetectors (QWIPs) based on a bound-to-bound intersubband transition in GaAs/AlGaAs. The responsivity is comparable with that of mid-infrared GaAs/AlGaAs and InGaAs/GaAs QWIPs. A peak responsivity of 0.265 A/W and detectivity of 2.5×109 cmmath/W at a wavelength of 26.9 μm and 4.2 K have been achieved. Based on the temperature dependent dark current and responsivity results, it is expected that similar performance can be obtained at least up to 20 K. © 1998 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
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