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22 Oct 1990

Volume 57, Issue 17, pp. 1709-1827

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High‐current lattice‐strained In0.59Ga0.41As/In0.52Al0.48As modulation‐doped field‐effect transistors grown by molecular beam epitaxy

J. B. Kuang, Y. K. Chen, D. Sivco, A. Y. Cho, and L. F. Eastman

Appl. Phys. Lett. 57, 1784 (1990); http://dx.doi.org/10.1063/1.104041 (3 pages) | Cited 7 times

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High‐current driving capability is realized in submicron‐gate lattice‐strained In0.59Ga0.41As/In0.52Al0.48As (Δa/a=4×10−3) modulation‐doped field‐effect transistors. Full‐channel drain current in excess of 1.10 and 1.90 A/mm are obtained at 80 K for the singly doped and doubly doped structure, respectively. By using the double modulation technique and a buried p‐buffer layer, excellent high‐frequency performance and flat transconductance characteristics were realized over a very broad range of gate and drain bias voltages. These devices are very suitable for large‐signal or power device operations. The high quality In0.52Al0.48As buffer layer eliminates the hysteresis and current instability (or the kink effect) in submicron‐gate devices at both 300 and 80 K.
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85.30.Tv Field effect devices
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Ey III-V semiconductors

Charge injection logic

Serge Luryi, Piotr M. Mensz, Mark R. Pinto, Paul A. Garbinski, Alfred Y. Cho, and Deborah L. Sivco

Appl. Phys. Lett. 57, 1787 (1990); http://dx.doi.org/10.1063/1.104022 (3 pages) | Cited 25 times

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The charge injection transistor is a semiconductor device based on transfer of hot electrons between separately contacted conducting layers. The nature of hot‐electron injection by the real‐space transfer allows the implementation of novel circuit elements. In particular, we propose a multiterminal single‐device structure that works as a functional element with three logic inputs Xj (j=1,2,3) and one output equal to (X1∩X2∩X3)∪(X1∩X2∩X3). This device, called the norand, can perform both as a nor(X1,X2) and as an and(X1,X2) element, reprogrammable electrically by changing the X3 input. The operation of norand with logic gain is demonstrated experimentally by an equivalent circuit connection of discrete charge injection transistors implemented within InGaAs/InAlAs on InP technology.
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85.30.De Semiconductor-device characterization, design, and modeling
07.50.Ek Circuits and circuit components

Intersubband infrared absorption in a GaAs/Al0.3Ga0.7As quantum well structure

M. O. Manasreh, F. Szmulowicz, D. W. Fischer, K. R. Evans, and C. E. Stutz

Appl. Phys. Lett. 57, 1790 (1990); http://dx.doi.org/10.1063/1.104023 (3 pages) | Cited 34 times

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The linewidth, total integrated area, and peak position (ν0) of the intersubband transition (IT) in a GaAs/Al0.3Ga0.7As multiple quantum well, with doping in the barrier, are studied as a function of temperature using the infrared absorption technique. From the temperature dependence of the linewidth and the configuration coordinate model we find that the electrons in the GaAs well are weakly coupled to the GaAs normal optical phonon mode. The electron density (σ) in the quantum well is extracted from the total integrated area of the IT. From the temperature‐dependence of σ we conclude that the Fermi energy is also temperature dependent and that at 5 K it is about 36 meV above the ground state energy. We also find that ν0 increases as the temperature decreases. We calculated the absorption spectrum for the quantum well in a nonparabolic‐anisotropic envelope function approximation including temperature‐dependent effective masses, nonparabolicity, conduction‐band offsets, the Fermi level, and line shape broadening. Our results indicate that a large many‐body correction, in particular an exchange interaction for the ground state, is necessary to account for the experimental peak position and blue shift as the temperature is lowered.
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78.30.Fs III-V and II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.70.Gm Exchange interactions
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

Ion beam enhanced epitaxial growth of Ge (001)

E. Chason, P. Bedrossian, K. M. Horn, J. Y. Tsao, and S. T. Picraux

Appl. Phys. Lett. 57, 1793 (1990); http://dx.doi.org/10.1063/1.104024 (3 pages) | Cited 39 times

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An enhancement in surface smoothness during molecular beam epitaxial growth of Ge on Ge (001) by 200 eV Xe ion bombardment has been measured with reflection high‐energy electron diffraction. We show that the steady‐state surface is smoother during simultaneous ion bombardment and growth at 400 °C than during ion bombardment or growth alone. The smoothest surface is obtained when the rate of deposition is approximately equal to the rate of production of ion‐induced surface defects. It is suggested that the smoothening is the consequence of the ion‐induced vacancy‐like defects annihilating with surface atoms and/or destabilizing small clusters.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.80.Jh Ion radiation effects
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Origin and improvement of interface roughness in AlGaAs/GaAs heterostructures grown by molecular beam epitaxy

Naresh Chand and S. N. G. Chu

Appl. Phys. Lett. 57, 1796 (1990); http://dx.doi.org/10.1063/1.104025 (3 pages) | Cited 15 times

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We show that the likely reason of interface roughness of AlxGa1−xAs/GaAs heterostructures is the surface segregation of background impurities present in the AlGaAs layer. The roughness increases with x and is worse for x=1. In our system, Al is considered to be the main source of impurities in AlGaAs. When grown using a less pure Al source, AlxGa1−xAs/GaAs interfaces show waviness with wavelength ranging from a few hundred to few thousand Å even for x=0.1. Such wavy AlGaAs/GaAs interfaces were not observed when a purer Al source was used irrespective of the AlGaAs thickness, value of x, growth rate, growth temperature (<630 °C), As4:Ga flux ratio, and other growth conditions. The AlAs/GaAs interface smoothness was further improved by using 2° to 4° off (100) towards 〈111〉A GaAs substrates, and by incorporating thin layers of GaAs at regular intervals in AlAs.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
71.55.Eq III-V semiconductors
68.35.Fx Diffusion; interface formation
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Secondary‐ion mass spectrometry on δ‐doped GaAs grown by molecular beam epitaxy

E. F. Schubert, H. S. Luftman, R. F. Kopf, R. L. Headrick, and J. M. Kuo

Appl. Phys. Lett. 57, 1799 (1990); http://dx.doi.org/10.1063/1.104026 (3 pages) | Cited 18 times

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Improved resolution of secondary‐ion mass spectrometry (SIMS) is obtained on Be δ‐doped GaAs grown by molecular beam epitaxy at a temperature of 500 °C. The measured impurity distribution width is 29 Å, which corresponds to a SIMS resolution of ΔzR=25 Å. Impurity diffusion lengths of ≤10 Å can be detected by the technique. The surface segregation of Si impurities in δ‐doped GaAs grown at 660 °C is investigated as a function of doping density. The segregation length increases with the Si density and is consistent with a segregation model based on the pinning of the Fermi level at the growing GaAs surface.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
66.30.J- Diffusion of impurities
73.20.At Surface states, band structure, electron density of states
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

GaAs/GaInP multiquantum well long‐wavelength infrared detector using bound‐to‐continuum state absorption

S. D. Gunapala, B. F. Levine, R. A. Logan, T. Tanbun‐Ek, and D. A. Humphrey

Appl. Phys. Lett. 57, 1802 (1990); http://dx.doi.org/10.1063/1.104027 (3 pages) | Cited 24 times

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We demonstrate an 8 μm superlattice infrared detector which utilizes bound‐to‐continuum state intersubband absorption in lattice‐matched GaAs/Ga0.5In0.5P multiquantum well structures grown by atmospheric pressure metalorganic vapor phase epitaxy. The band offsets of the GaAs/Ga0.5In0.5P heterosystem are obtained by comparing the theoretical absorption spectrum and the measured responsivity spectrum. The values determined for ΔEc and ΔEv are 221 and 262 meV, respectively.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
78.66.Fd III-V semiconductors
78.66.Hf II-VI 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

Pulsed excimer laser deposition Y1Ba2Cu3O7−x superconductor films on silicon with laser‐deposited Y‐ZrO2 buffer layer

S. B. Ogale, R. D. Vispute, and R. R. Rao

Appl. Phys. Lett. 57, 1805 (1990); http://dx.doi.org/10.1063/1.104142 (3 pages) | Cited 17 times

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The pulsed excimer laser ablation method is used to deposit both the buffer layer of Y‐stabilized ZrO2 and the overlayer of Y1Ba2Cu3O7−x superconductor on (100) oriented single‐crystal silicon. Process parameter optimization study is carried out and it is shown that a thin film of the superconductor (0.5–0.7 μm) having a zero resistance temperature of 86 K can be obtained using a 0.3 μm buffer layer deposited at substrate temperatures between 600 and 800 °C.
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74.78.-w Superconducting films and low-dimensional structures
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
74.70.-b Superconducting materials other than cuprates

Cathodoluminescence study of thin films of high Tc superconductors

Z. Barkay, J. Azoulay, Y. Lereah, U. Dai, N. Hess, D. Racah, E. Grünbaum, and G. Deutscher

Appl. Phys. Lett. 57, 1808 (1990); http://dx.doi.org/10.1063/1.104028 (3 pages) | Cited 6 times

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Cathodoluminescence (CL) of thin films of high Tc superconductors was studied in the scanning electron microscope. The depth and the lateral locations of the different phases can be revealed. In thin films, unlike the bulk superconductors, the CL information can be obtained either from the film itself or the substrate by varying the primary beam energy. At high beam energy, substrate defects and slight thickness variations of a single high Tc phase are observed. The resolution of the CL measurements improves at low temperatures.
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78.60.Hk Cathodoluminescence, ionoluminescence
74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
68.55.Nq Composition and phase identification

Crossover from tunneling to metallic behavior in superconductor‐semiconductor contacts

A. W. Kleinsasser, T. N. Jackson, D. McInturff, F. Rammo, G. D. Pettit, and J. M. Woodall

Appl. Phys. Lett. 57, 1811 (1990); http://dx.doi.org/10.1063/1.104029 (3 pages) | Cited 43 times

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We describe current‐voltage measurements on superconducting Nb/InGaAs junction field‐effect transistors which reveal a crossover from tunneling‐dominated to Andreev scattering‐dominated transport at the superconductor‐semiconductor contacts as Schottky barrier thickness decreases with increasing interfacial dopant concentration. These measurements are the first demonstration of such a crossover in a thin‐film structure, and are of interest for investigations of hybrid superconductor‐semiconductor devices, proximity effect boundary conditions, and transport in ohmic contacts to semiconductors.
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85.30.Tv Field effect devices
74.50.+r Tunneling phenomena; Josephson effects
85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices
73.40.Sx Metal-semiconductor-metal structures

Origin of surface roughness for c‐axis oriented Y‐Ba‐Cu‐O superconducting films

C. C. Chang, X. D. Wu, R. Ramesh, X. X. Xi, T. S. Ravi, T. Venkatesan, D. M. Hwang, R. E. Muenchausen, S. Foltyn, and N. S. Nogar

Appl. Phys. Lett. 57, 1814 (1990); http://dx.doi.org/10.1063/1.104143 (3 pages) | Cited 70 times

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One problem with the growth of high quality c‐axis oriented YBa2Cu3O7−x films is the tendency of the film surface to become rough. We studied the film growth mechanism as a function of deposition rate using pulsed laser deposition. These films form by the classic nucleation and growth process; the thickness at which the nucleated islands coalesce increased with decreasing deposition rate. The film has pinholes prior to coalescence and nucleates outgrowths during coalescence. The outgrowths enlarge rapidly because they contain materials and crystallographic directions with growth rates faster than that of the c‐axis film. A smooth surface is obtained if the substrate temperature and deposition rate are chosen such that coalescence is just completed at the final film thickness. We observed the outgrowths nucleating at coalescence and propose that certain defects, related to the c‐axis growth habit, may be the fundamental cause of outgrowth formation. Outgrowths have not been observed in a‐axis films. Outgrowths are easily confused with the particulate deposition problem associated with laser deposition. In these experiments, the particulate problem was essentially eliminated by using freshly polished targets for each run.
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74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures
68.35.Gy Mechanical properties; surface strains
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

180° surface domain wall magnetization profiles: Comparisons between scanning electron microscopy with polarization analysis measurements, magneto‐optic Kerr microscopy measurements and micromagnetic models

M. R. Scheinfein, P. J. Ryan, J. Unguris, D. T. Pierce, and R. J. Celotta

Appl. Phys. Lett. 57, 1817 (1990); http://dx.doi.org/10.1063/1.104144 (3 pages) | Cited 5 times

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We compare measurements of magnetization profiles across a 180° surface domain wall in a 0.24‐μm‐thick of Permalloy (Ni81Fe19), obtained with scanning electron microscopy with polarization analysis (SEMPA) and longitudinal magneto‐optic (MO) Kerr microscopy with the predictions of a bulk micromagnetic theory. Both measurement techniques yield wall profiles in accordance with the predictions of micromagnetic theory. We conclude that for micromagnetic structure with relevant length scales on the order of tens of nanometers, SEMPA and MO Kerr microscopy yield equivalent quantitative micromagnetic information within the transverse spatial resolution limits of each technique. Near‐surface effects such as enhanced surface moments, weakened surface exchange, and surface anisotropy are not important in determining the surface domain wall profiles that we observe.
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75.60.Ch Domain walls and domain structure
75.50.Bb Fe and its alloys

Batch fabricated sensors for magnetic force microscopy

P. Grütter, D. Rugar, H. J. Mamin, G. Castillo, S. E. Lambert, C.‐J. Lin, R. M. Valletta, O. Wolter, T. Bayer, and J. Greschner

Appl. Phys. Lett. 57, 1820 (1990); http://dx.doi.org/10.1063/1.104030 (3 pages) | Cited 40 times

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In this letter we describe force sensors suitable for magnetic force microscopy (MFM) made by coating silicon microcantilevers with various thin magnetic films. These MFM force sensors can be batch fabricated and their magnetic properties tailored by choosing appropriate coatings. This is demonstrated by analyzing the MFM response for magnetization patterns written on a longitudinal recording test sample. Selectable components of the sample stray field can be measured by coating the tips with high coercivity films. Tips coated with low coercivity films such as Permalloy respond to the total stray field. Sample perturbations due to the tip stray field are small for thin‐film tips, allowing the imaging of low coercivity samples such as Permalloy.
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07.55.-w Magnetic instruments and components
75.70.Ak Magnetic properties of monolayers and thin films
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.50.Vv High coercivity materials

State of bismuth in BaBiO3 and BaBi1−xPbxO3: Bi 4f photoemission and Bi L3 absorption spectroscopic studies

G. U. Kulkarni, V. Vijayakrishnan, G. Ranga Rao, Ram Seshadri, and C. N. R. Rao

Appl. Phys. Lett. 57, 1823 (1990); http://dx.doi.org/10.1063/1.104145 (2 pages) | Cited 8 times

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The 2p 6d feature in the Bi L3 spectra has different energies in the semiconducting (0.0≤x<0.7) and the superconducting (x=0.75) compositions of BaBi1−xPbxO3. The Bi 4f core level spectrum shows distinct features ascribable to Bi III and Bi V in BaBiO3 and in the semiconducting compositions; the width of the 4f peaks is also considerably larger in these compositions compared to that in BaBi0.25Pb0.75O3, which shows a single sharp Bi 4f feature.
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79.60.-i Photoemission and photoelectron spectra
74.70.-b Superconducting materials other than cuprates
78.30.-j Infrared and Raman spectra
78.40.-q Absorption and reflection spectra: visible and ultraviolet

Metastable states of a low‐frequency mesodynamic pendulum

Randall D. Peters

Appl. Phys. Lett. 57, 1825 (1990); http://dx.doi.org/10.1063/1.104031 (3 pages) | Cited 4 times

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A preliminary study has been made of the free decay of a physical pendulum whose mass is dominated by two metal bobs, and whose period can be adjusted to exceed 30 s. The decay mechanism is predominantly anelasticity from internal friction of creep. The relaxation spectrum of this creep suggests a mechanical Barkhausen effect. In surprising contrast to exponential decay at large energy, the motion at low energy and long period is characterized by repeatable metastable states. Phase is preserved in the transition between most states even though the transitions may be chaotic. There is a lowest harmonic state which is different for Pb and Cu bobs, and below which the system transitions from free decay to stochastic fluctuation‐dissipation. Noise of this stochastic state is larger than electronic noise, and power spectral density plots show that it contains mixtures of subharmonics at integral multiples of 1/4 the pendulum frequency.
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45.05.+x General theory of classical mechanics of discrete systems
04.90.+e Other topics in general relativity and gravitation (restricted to new topics in section 04)
62.30.+d Mechanical and elastic waves; vibrations
06.20.-f Metrology
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