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30 May 1994

Volume 64, Issue 22, pp. 2913-3050

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Role of hot electron base transport in abrupt emitter InP/Ga0.43In0.53As heterojunction bipolar transistors

Dan Ritter, R. A. Hamm, A. Feygenson, and P. R. Smith

Appl. Phys. Lett. 64, 2988 (1994); http://dx.doi.org/10.1063/1.111380 (3 pages) | Cited 8 times

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The high frequency performance of InP/Ga0.47In0.53As heterojunction bipolar transistors (HBTs) with a varying base thickness was measured. The diffusion constant of minority carrier electrons in the heavily doped base was found to be 105 cm2/s. It is demonstrated that the short base transit times in fast InP/Ga0.47In0.53As HBTs is mainly due to the high value of the diffusion constant of thermalized electrons. The contribution of hot electron ballistic transport is relatively small.
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85.30.Pq Bipolar transistors
73.61.Ey III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Band discontinuity of strained‐layer GaInAs/GaInAsP heterostructures

I. Queisser, V. Härle, A. Dörnen, and F. Scholz

Appl. Phys. Lett. 64, 2991 (1994); http://dx.doi.org/10.1063/1.111381 (3 pages) | Cited 4 times

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We performed low temperature photoluminescence excitation and photocurrent measurements on tensile and compressively strained GaxIn1−xAs quantum‐well layers grown on GaInAsP, which was lattice matched to the InP substrate. From these measurements the excitonic transitions in the unstrained and strained samples can be identified. We determine the effective masses in growth direction GaxIn1−xAs (0.3<xGa<0.6) and the band offsets of the GaxIn1−xAs/GaInAsP heterojunction (0.4<xGa<0.6).
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73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors

Hysteresis of trapped charge in AlGaSb barrier as a mechanism for the current bistability in AlGaSb/InAs/AlGaSb double‐barrier structures

F. A. Buot and A. K. Rajagopal

Appl. Phys. Lett. 64, 2994 (1994); http://dx.doi.org/10.1063/1.111382 (3 pages) | Cited 9 times

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See Also: Erratum

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A simple theory of charge buildup and bistability is used to show that the new hysteresis and bistability in the current‐voltage behavior recently reported in AlGaSb/InAs/AlGaSb double‐barrier structures is directly related to the bistability and hysteresis in the hole population of the AlGaSb barrier layer. This occurs well before the resonant‐tunneling‐current peak.
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73.40.Gk Tunneling
72.20.Ht High-field and nonlinear effects
85.30.De Semiconductor-device characterization, design, and modeling
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Optical properties near the band gap on hexagonal and cubic GaN

H. Okumura, S. Yoshida, and T. Okahisa

Appl. Phys. Lett. 64, 2997 (1994); http://dx.doi.org/10.1063/1.111383 (3 pages) | Cited 44 times

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We have measured the photoluminescence and optical reflection spectra of cubic and hexagonal GaN films epitaxially grown on GaAs and 3C‐SiC substrates by gas‐source molecular beam epitaxy using microwave‐activated NH3 source. The crystalline quality of the epilayers was improved by using an activated NH3 beam and 3C‐SiC substrates, which enabled us to obtain intense optical signals. The measured spectra suggest that the band gap of cubic GaN is around 190 meV smaller than that of hexagonal GaN.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
61.66.Fn Inorganic compounds
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Effect of carbonization on the growth of 3C‐SiC on Si (111) by silacyclobutane

C. Yuan, A. J. Steckl, and M. J. Loboda

Appl. Phys. Lett. 64, 3000 (1994); http://dx.doi.org/10.1063/1.111384 (3 pages) | Cited 20 times

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Chemical vapor deposition of SiC on Si (111) from silacyclobutane (c‐C3H6SiH2, SCB) has been carried out on propane carbonized and on virgin Si substrates. The carbonization was performed at 760 Torr and the SiC growth at 5 Torr. Transmission electron diffraction (TED) and x‐ray diffraction were used to determine the crystallinity of the resulting films. The minimum temperature for obtaining crystalline films, as indicated by a TED pattern consisting of sharp spots with (111) SiC crystal hexagonal symmetry, was lower with carbonization (∼800–900 °C) than without (∼1000 °C). However, the carbonization process creates voids in the Si just below the SiC/Si interface, while SCB growth without carbonization produces a very smooth and void‐free interface. Fourier‐transform infrared measurements of SiC films grown at 1200 °C without carbonization exhibit a sharp (full width at half‐maximum=30 cm−1) Si‐C absorption peak at 794 cm−1.
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81.65.-b Surface treatments
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.05.cf X-ray scattering (including small-angle scattering)
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.

Very long‐wavelength GaAs/AlxGa1−xAs infrared hot electron transistor

S. D. Gunapala, J. S. Park, T. L. Lin, J. K. Liu, and K. M. S. V. Bandara

Appl. Phys. Lett. 64, 3003 (1994); http://dx.doi.org/10.1063/1.111385 (3 pages) | Cited 1 time

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We have demonstrated a bound‐to‐continuum state GaAs/AlxGa1−xAs infrared hot electron transistor which has a peak response at λp=16.3 μm. This device utilizes a bound‐to‐continuum quantum well infrared photodetector as a photosensitive emitter and a wide AlxGa1−xAs barrier between the base and the collector as an energy discriminating filter. An excellent photocurrent transfer ratio of αp=0.12 and very low dark current transfer ratio of αd=7.2×10−5 is achieved at a temperature of T=60 K.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
72.40.+w Photoconduction and photovoltaic effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Blue light emission from silicon surfaces prepared by spark‐erosion and related techniques

D. Rüter, T. Kunze, and W. Bauhofer

Appl. Phys. Lett. 64, 3006 (1994); http://dx.doi.org/10.1063/1.111386 (3 pages) | Cited 32 times

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We have investigated the photoluminescence (PL) of silicon surfaces treated by spark‐erosion and related techniques as a function of gas composition and pressure. PL emission in the wavelength range of 400–550 nm and with decay times ≤5 ns has been observed. PL quantum efficiencies comparable to that of standard wet chemically prepared porous silicon are obtained. We have never found significant PL emission in the red spectral range. Our dry plasma techniques for the preparation of luminescent silicon surfaces are a promising alternative to the common anodizing process in hydrofluoric solutions.
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78.55.Hx Other solid inorganic materials
78.66.Bz Metals and metallic alloys

Transient space‐charge‐limited currents: The time‐of‐flight and post‐transit analysis in hydrogenated amorphous silicon

F. Schauer, A. Eliat, M. Nesládek, and G. J. Adriaenssens

Appl. Phys. Lett. 64, 3009 (1994); http://dx.doi.org/10.1063/1.111387 (3 pages) | Cited 4 times

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Through evaluation of the post‐transit part of the transient space‐charge‐limited currents (SCLC), it becomes possible to determine the hydrogenated amorphous silicon (a‐Si:H) density of localized states (DOS) over a wide range of energies. The use of SCLC conditions results in the enhancement of the occupation of the deep states and hence in the corresponding increase of the signal. In combination with standard SCLC time‐of‐flight, and since it can be used for both electrons and holes, the method is suitable for the elucidation of the complete DOS distribution, for the examination of the emission times of deep traps, and for the determination of carrier drift mobilities, all on the same p‐i‐n structure (which may be a standard solar cell).
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73.50.Pz Photoconduction and photovoltaic effects
73.61.Jc Amorphous semiconductors; glasses
72.80.Ng Disordered solids

New selective doping technique for boron using a HBO2 source and a thin oxide mask

Eiichi Murakami, Yoshio Kawamura, and Shin’ichiro Kimura

Appl. Phys. Lett. 64, 3012 (1994); http://dx.doi.org/10.1063/1.111388 (3 pages) | Cited 1 time

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Selective adsorption of HBO2 on Si(100) partially covered with thin (≲1 nm) oxide is observed using a Si molecular‐beam epitaxy system. The thin oxide is formed by local oxidation by a ArF excimer laser or wet chemical treatment. A selective adsorption rate of more than 20 is observed at 700 °C. After the adsorption, the oxide can be sublimated at 800 °C annealing in ultrahigh vacuum without boron desorption. These phenomena can be applied to selective shallow doping without photoresist.
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85.40.Hp Lithography, masks and pattern transfer
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
61.72.uf Ge and Si
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Transverse magnetoresistance: A novel two‐terminal method for measuring the carrier density and mobility of a semiconductor layer

Jeremiah R. Lowney, W. Robert Thurber, and David G. Seiler

Appl. Phys. Lett. 64, 3015 (1994); http://dx.doi.org/10.1063/1.111389 (3 pages) | Cited 13 times

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The magnetic‐field dependence of the two‐terminal magnetoresistance that occurs in rectangularly shaped samples can be used to determine both the free‐carrier density and the mobility of a semiconductor layer. An approximate equation for the magnetoresistance was derived for variable length‐to‐width ratio. This technique was used to determine the electron density and mobility of accumulation layers in n‐type Hg0.8Cd0.2Te photoconductive infrared detectors at 6 and 77 K. It should be applicable to a wide variety of fabricated devices and allow significant improvements in processing methods and quality control.
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72.20.My Galvanomagnetic and other magnetotransport effects
72.80.Ey III-V and II-VI semiconductors
73.25.+i Surface conductivity and carrier phenomena
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Large transconductances observed in an independently contacted coupled double quantum well

N. K. Patel, E. H. Linfield, K. M. Brown, M. P. Grimshaw, D. A. Ritchie, G. A. C. Jones, and M. Pepper

Appl. Phys. Lett. 64, 3018 (1994); http://dx.doi.org/10.1063/1.111390 (3 pages) | Cited 17 times

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Lateral transport in a coupled double quantum well has been studied in a system where each layer can be measured independently. Front and back gates were used to vary the carrier densities in the two wells and hence control the degree of electron coupling. When the carrier densities in the two 2DEGs were matched, the coupling was found to be strongest and resulted in a decrease in the resistance of the measured 2DEG. By using a structure with a low mobility 2DEG in parallel with a high mobility one, we demonstrate a device that displays large resistance changes and a correspondingly high transconductance.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Gk Tunneling

Growth of InSb using tris(dimethylamino)antimony and trimethylindium

K. C. Baucom and R. M. Biefeld

Appl. Phys. Lett. 64, 3021 (1994); http://dx.doi.org/10.1063/1.111391 (3 pages) | Cited 10 times

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We have grown epitaxial layers of InSb on p−‐InSb substrates by metalorganic chemical vapor deposition using tris(dimethylamino)antimony (TDMASb) and trimethylindium (TMIn). Growth temperatures from 285 to 500 °C and pressures from 76 to 660 Torr have been investigated. The V/III ratio was varied from 0.63 to 8.6 using growth rates from 0.06 to 0.67 μm/h. For temperatures ≤425 °C, the growth rate was proportional to the temperature. The growth rate was proportional to the TMIn flow at all temperatures. Temperatures ≳400 °C produced p‐type layers while growth temperatures ≤400 °C produce n‐type layers. The pyrolysis temperature of TDMASb appears to be lower than that of TMIn.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.61.Ey III-V semiconductors

Atomic vibration mediated electronic transport in amorphous silicon

C. M. Fortmann

Appl. Phys. Lett. 64, 3024 (1994); http://dx.doi.org/10.1063/1.111975 (3 pages) | Cited 2 times

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A new electron transport framework for amorphous silicon is presented. This new description describes electrons as being localized on atomic sites with the dominate conduction path being a high probability tunneling process between adjacent sites. This tunneling process is mediated by atomic positions and vibrations which are treated as perturbations in which the tunneling frequency is that of the atomic vibration. This theory of electron transport describes a wide range of observations including the temperature and pressure dependence of the mobility.
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73.61.Cw Elemental semiconductors

Mobility enhancement in double δ‐doped GaAs/InxGa1−xAs/GaAs pseudomorphic structures by grading the heterointerfaces

C. L. Wu, W. C. Hsu, H. M. Shieh, and W. C. Liu

Appl. Phys. Lett. 64, 3027 (1994); http://dx.doi.org/10.1063/1.111392 (3 pages) | Cited 3 times

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A novel double δ‐doped heterostructure employing symmetric graded InGaAs quantum wells as the active channel grown by low‐pressure metalorganic chemical vapor deposition (LP‐MOCVD) has been successfully fabricated. The proposed symmetrically graded InGaAs pseudomorphic structure manifests significantly improved electron mobility as high as 5300 (26 000) cm2/V s at 300 (77) K due to superior confinement and to the lower interface roughness scattering at GaAs/InGaAs heterointerfaces. We also carried out photoluminescence (PL) spectra and secondary‐ion mass spectrometry (SIMS) profiles to confirm the quality of the proposed structures.  
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.66.Fd III-V semiconductors
78.55.Bq Liquids

Determination of the superconducting current path in Bi2223/Ag tapes

J. H. Cho, M. P. Maley, J. O. Willis, J. Y. Coulter, L. N. Bulaevskii, P. Haldar, and L. R. Motowidlo

Appl. Phys. Lett. 64, 3030 (1994); http://dx.doi.org/10.1063/1.111393 (3 pages) | Cited 23 times

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We have measured the anisotropic transport properties of Bi2223/Ag tapes with and without the silver sheath. The anisotropy ratio of the resistivity along the rolling plane to the resistivity perpendicular to the rolling plane (∼4–10) is orders of magnitude smaller than single‐crystal anisotropy ratios. Results are consistent with current flow along crystallographic ab planes even for transport normal to the tape plane.
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74.72.-h Cuprate superconductors
74.25.Sv Critical currents
74.25.F- Transport properties

High transition temperature superconducting surface acoustic wave devices

H. Fredricksen, D. Ritums, N. J. Wu, X. Y. Li, A. Ignatiev, J. Feller, B. K. Sarma, and M. Levy

Appl. Phys. Lett. 64, 3033 (1994); http://dx.doi.org/10.1063/1.111397 (3 pages) | Cited 3 times

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Thin films of high transition temperature superconducting YBa2Cu3O7−δ (YBCO) have been deposited onto YZ‐cut LiNbO3 and photolithographically patterned into surface acoustic wave (SAW) devices operating at 50 and 100 MHz center frequencies. Both devices show sharp improvement in SAW transduction efficiency as temperatures are lowered to the superconducting transition temperature of the YBCO electrodes. The magnitude of the improvement is directly dependent on the normal state resistance of the YBCO, and in one case was as high as 12 dB. In both cases, the amplitude change over the entire temperature range is matched nearly exactly by the derived ideal electrode behavior predicted from the aperture width, substrate radiation resistance, and YBCO electrode sheet resistance.
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74.78.-w Superconducting films and low-dimensional structures
68.35.Gy Mechanical properties; surface strains
85.40.Hp Lithography, masks and pattern transfer
85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices

Transient resistive photoresponse of YBa2Cu3O7−δ films using low power 0.8 and 10.6 μm laser radiation

M. Lindgren, V. Trifonov, M. Zorin, M. Danerud, D. Winkler, B. S. Karasik, G. N. Gol’tsman, and E. M. Gershenzon

Appl. Phys. Lett. 64, 3036 (1994); http://dx.doi.org/10.1063/1.111398 (3 pages) | Cited 19 times

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Thin YBa2Cu3O7−δ laser deposited films were patterned into devices consisting of ten parallel 1 μm wide strips. Nonequilibrium picosecond and bolometric photoresponses were studied by the use of 17 ps full width at half‐maximum laser pulses and amplitude modulated radiation from an AlGaAs laser up to 10 GHz and from a CO2 laser up to 1 GHz. The time and frequency domain measurements were in agreement. The fast response can be explained by electron heating. The use of low optical power and a sensitive measurement system excluded any nonlinear transient processes and kinetic inductance changes in the superconducting state. At 1 GHz modulation frequency, the responsivity was ∼1.2 V/W both for 0.8 and 10.6 μm wavelengths. The sensitivity of a fast and spectrally broadband infrared detector is discussed.
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74.78.-w Superconducting films and low-dimensional structures
85.60.Gz Photodetectors (including infrared and CCD detectors)
74.72.-h Cuprate superconductors
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Heterodyne mixing with Nb tunnel junctions above the gap frequency

G. de Lange, C. E. Honingh, J. J. Kuipers, H. H. A. Schaeffer, R. A. Panhuyzen, T. M. Klapwijk, H. van de Stadt, and M. M. W. M. de Graauw

Appl. Phys. Lett. 64, 3039 (1994); http://dx.doi.org/10.1063/1.111399 (3 pages) | Cited 19 times

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The noise and gain of a heterodyne waveguide mixer employing Nb/Al2O3/Nb superconducting tunnel junctions with an on‐chip integrated tuning element are measured and analyzed at 680–750 GHz and at 840 GHz. The lowest receiver noise temperatures are 400 K (double side band) at 720 GHz and 1500 K (3000 K including the beam splitter loss) at 840 GHz. We compare data of the pumped I–V curves with the quantum theory of mixing and demonstrate good agreement at frequencies well above the gap frequency.
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74.78.Fk Multilayers, superlattices, heterostructures
74.40.-n Fluctuation phenomena
74.25.N- Response to electromagnetic fields
85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices

Selective trilayer deposition process for fabricating Nb/Al‐AlOx/Nb Josephson tunnel junctions

R. Monaco and A. Oliva

Appl. Phys. Lett. 64, 3042 (1994); http://dx.doi.org/10.1063/1.111371 (3 pages) | Cited 6 times

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High quality Nb/Al‐AlOx/Nb Josephson tunnel junctions have been fabricated using a novel process named the selective trilayer deposition process. The junction is formed on a patterned Nb underlayer through the lift‐off deposition of a Nb/Al‐AlOx/Nb trilayer. Anodization then provides the insulation between the underlayer and the wiring layer. We show that this easy and simple process is particularly advantageous for the fabrication of many vertically stacked tunnel junctions.
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85.25.Cp Josephson devices

Very large magnetoresistance in perovskite‐like La‐Ca‐Mn‐O thin films

M. McCormack, S. Jin, T. H. Tiefel, R. M. Fleming, Julia M. Phillips, and R. Ramesh

Appl. Phys. Lett. 64, 3045 (1994); http://dx.doi.org/10.1063/1.111372 (3 pages) | Cited 262 times

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Colossal magnetoresistance with more than a thousandfold change in resistivity (ΔR/RH=127 000% at 77 K, H=6 T) has been obtained in epitaxially grown La‐Ca‐Mn‐O thin films. This magnetoresistance value is about three orders of magnitude higher than is typically seen in the giant‐magnetoresistance‐type metallic, superlattice films. The temperature of peak magnetoresistance is located in the region of metallic resistivity behavior. As the magnetoresistance peak occurs not at the temperature of magnetic transition but at a temperature where the magnetization is still substantial, the spin‐disorder scattering is not likely to be the main mechanism in these highly magnetoresistive films. The peak can be shifted to near room temperature by adjusting processing parameters. Near‐room‐temperature ΔR/RH values of ∼1300% at 260 K and ∼400% at 280 K have been observed. The presence of grain boundaries appears to be very detrimental to achieving large magnetoresistance in the lanthanum manganite compounds. The fact that the electrical resistivity of a material can be manipulated by magnetic field to change by orders of magnitude could be useful for various device applications.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.61.-r Electrical properties of specific thin films
75.70.-i Magnetic properties of thin films, surfaces, and interfaces

Superconducting single crystals of TaC encapsulated in carbon nanotubes

Yositaka Yosida

Appl. Phys. Lett. 64, 3048 (1994); http://dx.doi.org/10.1063/1.111373 (3 pages) | Cited 18 times

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The synthesis and electron microscopic studies of TaC single crystals encapsulated in carbon nanotubes are reported. The crystal structure is the NaCl type with the lattice parameter a0=4.455±0.003 Å. The typical crystalline size is ∼7 nm. The epitaxial growth of carbon nanotube on the {100} plane of the TaC single crystal is observed. The statistical growth model is adequate for explaining the crystalline‐particle size distribution of the encapsulated crystals. Magnetic susceptibility measurements show a superconducting transition at 10.0 K, which is the expected critical temperature for the bulk TaC having the highest carbon composition.
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61.46.-w Structure of nanoscale materials
74.25.-q Properties of superconductors
81.20.-n Methods of materials synthesis and materials processing
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