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26 Mar 1990

Volume 56, Issue 13, pp. 1195-1292

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Band‐gap determination by photoreflectance of InGaAs and InAlAs lattice matched to InP

D. K. Gaskill, N. Bottka, L. Aina, and M. Mattingly

Appl. Phys. Lett. 56, 1269 (1990); http://dx.doi.org/10.1063/1.102533 (3 pages) | Cited 62 times

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Photoreflectance‐derived band‐gap parameters as a function of temperature for InGaAs and InAlAs lattice matched to InP are reported. The experiment was performed on a set of samples of various compositions (and strains) yielding greater reliability and ensuring self‐consistency. For InGaAs, fits to the Varshni equation gave E0(T=0 K)=803 meV, α=4.0×10−4 eV K−1, and β=226 K. For InAlAs, E0(T=0 K)=1.541 eV, α=4.7×10−4 eV K−1, β=149 K, and Δ0=338 meV.
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68.55.Nq Composition and phase identification
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

Influence of GaAs surface stoichiometry on the interface state density of as‐grown epitaxial ZnSe/epitaxial GaAs heterostructures

J. Qiu, Q.‐D. Qian, R. L. Gunshor, M. Kobayashi, D. R. Menke, D. Li, and N. Otsuka

Appl. Phys. Lett. 56, 1272 (1990); http://dx.doi.org/10.1063/1.102534 (3 pages) | Cited 37 times

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Epitaxial ZnSe/epitaxial GaAs interfaces have been formed by molecular beam expitaxy and evaluated by several techniques including capacitance‐voltage measurements. In the study reported here, the GaAs surface stoichiometry was systematically varied prior to the nucleation of ZnSe. A dramatic reduction of interface state density occurred when the GaAs epilayer was made As deficient. The resulting interface state densities of as‐grown structures are comparable to values obtained with (Al,Ga)As/GaAs interfaces.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Silicon vapor phase epitaxial growth catalysis by the presence of germane

P. M. Garone, J. C. Sturm, P. V. Schwartz, S. A. Schwarz, and B. J. Wilkens

Appl. Phys. Lett. 56, 1275 (1990); http://dx.doi.org/10.1063/1.102535 (3 pages) | Cited 65 times

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Experiments involving the epitaxial growth of GexSi1−x films by chemical vapor deposition have shown that the addition of germane greatly enhances the growth rate, compared to that seen with dichlorosilane alone. Careful analysis shows that the increase is not accounted for by summing the individual growth rates, but clearly indicates that the silicon growth rate is catalyzed. The magnitude of the effect increases at lower temperatures, with a two orders of magnitude increase seen at 625 °C.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Characterization of GaAs/Ga1−xAlxAs heterojunction bipolar transistor structures using photoreflectance

X. Yin, Fred H. Pollak, L. Pawlowicz, T. O’Neill, and M. Hafizi

Appl. Phys. Lett. 56, 1278 (1990); http://dx.doi.org/10.1063/1.102536 (3 pages) | Cited 63 times

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We have studied the photoreflectance spectra at 300 K from a number of GaAs/Ga1−x AlxAs heterojunction bipolar transistor (HBT) structures grown by molecular beam epitaxy and metalorganic chemical vapor deposition. From the observed Franz–Keldysh oscillations we have been able to evaluate the built‐in dc electric fields Fdc in the Ga1−x Alx As emitter as well as the n−‐GaAs collector region. In addition, the Ga1−x Alx As band gap (and hence Al composition) has been determined. The obtained values of Fdc are in good agreement with numerically computed values for the analyzed HBT structures, thus making it possible to deduce doping levels in these sections.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
78.40.Ha Other nonmetallic inorganics
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

(Tl, Pb, Bi)Sr2Ca2Cu3Oz superconductors with zero resistance at 120 K

Tetsuyuki Kaneko, Takahiro Wada, H. Yamauchi, and Shoji Tanaka

Appl. Phys. Lett. 56, 1281 (1990); http://dx.doi.org/10.1063/1.103174 (3 pages) | Cited 11 times

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We have synthesized new superconductors of nearly single phase with zero‐resistance temperatures around 120 K employing a novel method for sintering. The samples included a nominal composition of (Tl0.64Pb0.2Bi0.16)Sr2Ca3Cu4Oz. This sample was prepared from the mixture of presynthesized (Tl0.64Pb0.2Bi0.16)Sr2CaCu2Oz (1212 phase), CaO, and CuO powders. The mixed powder was sintered at 920 °C in O2 gas and post‐annealed at 400–600 °C in O2 gas. The powder x‐ray diffraction revealed that the sample was isostructural with the Tl‐based (Tl, Pb, Bi)Sr2Ca2Cu3Oz (1223 phase). The sample exhibited a sharp superconducting transition at Tonsetc=125 K and TR=0c=120 K and the superconducting diamagnetic signal at 10 K was about 20% of a full Meissner effect.
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74.70.-b Superconducting materials other than cuprates
74.10.+v Occurrence, potential candidates
61.66.Fn Inorganic compounds
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

Strong magnetic field dependence of the critical currents correlated to the microstructure of YBaCuO ceramics

Uri Dai, Guy Deutscher, Claude Lacour, Francine Laher‐Lacour, Philippe Mocaër, and Michel Laguës

Appl. Phys. Lett. 56, 1284 (1990); http://dx.doi.org/10.1063/1.102537 (3 pages) | Cited 6 times

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Critical currents of YBaCuO ceramics were measured at 77 K by transport measurements in an applied magnetic field H. A hysteretic behavior between 10 and 10 000 G was observed. For decreasing fields, the critical current Jc obeys a power law H−n with n ranging between 0.6 and 2.8. The exponent n is correlated with the microstructure and the average grain size of the ceramic. This power law behavior is discussed in terms of modified flux creep and flux flow regimes related to the microstructure.
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74.25.Sv Critical currents
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.78.Fk Multilayers, superlattices, heterostructures
74.70.-b Superconducting materials other than cuprates

Enhanced flux pinning by phase decomposition in Y‐Ba‐Cu‐O

S. Jin, T. H. Tiefel, S. Nakahara, J. E. Graebner, H. M. O’Bryan, R. A. Fastnacht, and G. W. Kammlott

Appl. Phys. Lett. 56, 1287 (1990); http://dx.doi.org/10.1063/1.103335 (3 pages) | Cited 52 times

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Significantly improved flux pinning has been achieved in bulk YBa2Cu3O7−δ superconductor (‘‘123’’ compound) containing fine‐scale defects (<∼50 Å thick). The measured Jc intragrain of ∼105 A/cm2 at 77 K, H=0.9 T is about ten times higher than the typical values for bulk Y‐Ba‐Cu‐O. The improved structure was produced by rapid decomposition at 920 °C of the YBa2Cu4O8 (‘‘124’’) precursor. This new and simple processing route could lead to a commercially viable processing technique for flux‐pinning enhancement in bulk Y‐Ba‐Cu‐O.
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74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Sv Critical currents
61.72.Nn Stacking faults and other planar or extended defects
64.70.K- Solid-solid transitions

Electron focusing in two‐dimensional systems by means of an electrostatic lens

J. Spector, H. L. Stormer, K. W. Baldwin, L. N. Pfeiffer, and K. W. West

Appl. Phys. Lett. 56, 1290 (1990); http://dx.doi.org/10.1063/1.102538 (3 pages) | Cited 62 times

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We introduce an electrostatic lens for ballistic electrons in two‐dimensional (2D) systems and demonstrate its focusing action in very high mobility GaAs‐(AlGa)As heterostructures. This is the first refractive element for the control of 2D electrons. It exemplifies the close analogy between ballistic propagation in 2D electron systems and traditional geometrical optics.
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85.30.Tv Field effect devices
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Dn Low-field transport and mobility; piezoresistance
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
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