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18 Jun 1990

Volume 56, Issue 25, pp. 2487-2586

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Improved minority‐carrier lifetime in Si/SiGe heterojunction bipolar transistors grown by molecular beam epitaxy

G. S. Higashi, J. C. Bean, C. Buescher, R. Yadvish, and H. Temkin

Appl. Phys. Lett. 56, 2560 (1990); http://dx.doi.org/10.1063/1.102886 (3 pages) | Cited 13 times

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Noncontact‐probe photocarrier lifetime measurements have been used to give rapid feedback on minority‐carrier lifetimes of epitaxial Si/SiGe layers grown by molecular beam epitaxy (MBE). In this manner, problems with impurity incorporation during the crystal growth can be rapidly diagnosed in a device‐processing‐independent fashion. These improvements in minority‐carrier lifetime translate directly into high gains in the heterojunction bipolar transistors (HJBTs). HJBT test devices fabricated from the MBE‐grown Si/SiGe layers show current gains as high as 800. The homojunction gain of this device is estimated to be ∼6, making the heterojunction gain on the order of 130.
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85.30.Pq Bipolar transistors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Cw Elemental semiconductors

Real‐space transfer in three‐terminal InGaAs/InAlAs/InGaAs heterostructure devices

Piotr M. Mensz, Serge Luryi, Alfred Y. Cho, Deborah L. Sivco, and Fan Ren

Appl. Phys. Lett. 56, 2563 (1990); http://dx.doi.org/10.1063/1.102889 (3 pages) | Cited 18 times

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Three‐terminal real‐space transfer devices have been implemented in InGaAs/InAlAs/InGaAs heterostructure material. The use of nonalloyed contacts provides excellent ohmic contacts to the channel without compromising insulation from the second conducting layer, The observed negative differential resistance has a peak‐to‐valley ratio that typically exceeds 100, both at room temperature and cryogenic temperatures. The highest observed peak‐to‐valley ratio at 300 K was 490. With increasing heating voltage, the injection current across the InAlAs barrier rises in a sequence of sharp steps. We explain this feature by an instability caused by a positive feedback between the heating field in the channel and the local real‐space transfer current.
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72.20.Ht High-field and nonlinear effects
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.De Semiconductor-device characterization, design, and modeling
73.61.Ey III-V semiconductors

Characterization of nanostructures by reflection electron microscopy

A. Scherer and B. P. Van der Gaag

Appl. Phys. Lett. 56, 2566 (1990); http://dx.doi.org/10.1063/1.102867 (3 pages) | Cited 2 times

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We use reflection electron microscopy (REM) to analyze ion‐etched nanostructures defined in compound semiconductor heterostructures. This nondestructive imaging technique allows us to characterize 10‐nm‐wide features with high resolution and determine their sidewall morphology on a 1 nm scale. In addition to the inherent high‐resolution available from REM, we also obtain diffraction contrast from the heterostructure material, and we can image quantum wells. We routinely use this technique to characterize and accurately measure microfabricated structures with lateral dimensions below 20 nm.
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85.40.Hp Lithography, masks and pattern transfer
81.65.-b Surface treatments
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Application of ellipsometry to crystal growth by organometallic molecular beam epitaxy

D. E. Aspnes, W. E. Quinn, and S. Gregory

Appl. Phys. Lett. 56, 2569 (1990); http://dx.doi.org/10.1063/1.102868 (3 pages) | Cited 61 times

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We report the first use of ellipsometry as a real‐time monitor of III‐V semiconductor crystal growth by molecular beam epitaxy, specifically growth of GaAs and AlGaAs from arsine, triethylgallium, and triethylaluminum sources. Our results provide new insight into the oxide desorption process and show a sensitivity of ±0.03 in compositions x>0.2 for 10 Å thickness increments of AlxGa1−xAs during initial deposition on GaAs.
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07.60.Fs Polarimeters and ellipsometers
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Nq Composition and phase identification
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

Absence of negative ion effects during on‐axis single target sputter depositions of Y‐Ba‐Cu‐O thin films on Si (100)

M. Migliuolo, R. M. Belan, and J. A. Brewer

Appl. Phys. Lett. 56, 2572 (1990); http://dx.doi.org/10.1063/1.102845 (3 pages) | Cited 17 times

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Stoichiometric thin films of YBa2Cu3O7−δ have been deposited on (100) silicon substrates by on‐axis single target magnetron sputtering. The effect of oxygen resputtering was minimized through the use of much stronger than usual magnetic assemblies in the source. A magnet assembly incorporating NdB and NdFeB magnets produced a magnetic field above the target twice as large as the one produced by a standard SmCo magnet assembly. This allows for the use of lower operating voltages and a better electron racetrack confinement, resulting in little or no oxygen resputtering. We have obtained stoichiometric or near‐stoichiometric films on silicon both by dc and rf magnetron techniques at a variety of sputtering pressures and target to substrate distances.
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81.15.Cd Deposition by sputtering
74.78.-w Superconducting films and low-dimensional structures

YBaCuO input coils with low Tc and high Tc SQUIDs

B. Oh, R. H. Koch, W. J. Gallagher, V. Foglietti, G. Koren, A. Gupta, and W. Y. Lee

Appl. Phys. Lett. 56, 2575 (1990); http://dx.doi.org/10.1063/1.102846 (3 pages) | Cited 8 times

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We have efficiently coupled single‐level YBaCuO (YBCO) input coils to superconducting quantum interference devices (SQUIDs) using coils and SQUIDs made on separate substrates and sandwiched together. At 4.2 K, the coupling efficiency α to a low noise Nb‐based SQUID was ∼0.76, with no increase in flux noise. At 77 K, the coupling efficiency of a YBCO coil to a TlBaCaCuO SQUID was ∼0.81. The magnetic field sensitivity of the coupled high Tc SQUID at 77 K was 9 pT/√Hz at 1000 Hz, a five times improvement compared to the bare SQUID.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.70.-b Superconducting materials other than cuprates
74.40.-n Fluctuation phenomena
74.25.N- Response to electromagnetic fields

Magnetic force microscopy of domain wall stray fields on single‐crystal iron whiskers

T. Göddenhenrich, H. Lemke, U. Hartmann, and C. Heiden

Appl. Phys. Lett. 56, 2578 (1990); http://dx.doi.org/10.1063/1.102847 (3 pages) | Cited 7 times

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Using a capacitively controlled force microscope we have imaged typical domain wall configurations like 90° closure structures and subdivided 180° wall segments in single‐crystal iron whiskers. Differences in wall contrast between 90° and 180° domain walls are clearly observed. The effect of tip‐to‐sample distance on lateral resolution and wall contrast in magnetic force microscopy is shown.
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07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
75.60.Ch Domain walls and domain structure
07.55.-w Magnetic instruments and components

High‐speed laser direct writing of tungsten conductors from W(CO)6

Y. Nambu, Y. Morishige, and S. Kishida

Appl. Phys. Lett. 56, 2581 (1990); http://dx.doi.org/10.1063/1.102848 (3 pages) | Cited 7 times

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High‐speed laser direct writing of tungsten conductors using tungsten‐hexacarbonyl [W(CO)6] is demonstrated. Tungsten lines were constructed on the Si‐LSI substrate at a writing speed as high as 300 μm/s with laser‐induced low‐pressure chemical vapor deposition. This speed is more than two orders of magnitude higher than the previously reported value for this material. Experiments are analyzed within the conventional three‐dimensional diffusion theory for the reactant. It has been found that the deposition rate limiting factor is the transport rate for the reactant into the reaction zone. The upper limit of the writing speed is predicted to be of the order of mm/s for the present material.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.40.Hp Lithography, masks and pattern transfer

Copper microcircuit repair of opens using thermally driven exchange plating

R. J. von Gutfeld and D. R. Vigliotti

Appl. Phys. Lett. 56, 2584 (1990); http://dx.doi.org/10.1063/1.102849 (3 pages) | Cited 5 times

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A two‐step method for the repair of circuit board defects consisting of complete opens is described. First, a small copper bridge is grown in unacidified copper sulfate solution by passing a few milliamperes of ac current at a frequency of 2–2000 kHz through the break. Local Joule heating results in copper deposition and bridging of the open via thermally driven exchange plating. For the second step, the cross section of the repair is increased by exchange plating in acid copper, using up to ∼1 A of ac current at a frequency on the order of 60 Hz or greater.
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85.40.Hp Lithography, masks and pattern transfer
82.45.-h Electrochemistry and electrophoresis
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
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