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20 Jul 1992

Volume 61, Issue 3, pp. 243-368

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Strained‐layer InGaAs quantum well lasers emitting at 1.5 μm grown by chemical beam epitaxy

Hideo Sugiura, Yoshio Noguchi, Ryuzo Iga, Takeshi Yamada, Hidehiko Kamada, Yoshihisa Sakai, and Hiroshi Yasaka

Appl. Phys. Lett. 61, 318 (1992); http://dx.doi.org/10.1063/1.108477 (3 pages) | Cited 3 times

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Laser characteristics of double channel planar buried heterostructure lasers with InxGa1−xAs/InGaAsP multiquantum wells (MQW) fabricated by a combination of chemical beam epitaxy and liquid phase epitaxy are described for the InAs content x of the InxGa1−xAs ranging from 0.53 to 0.71. There is no discernible difference in the minority carrier lifetime of the unstrained and strained MQWs. All the lasers have almost the same threshold current of 15±1 mA. Characteristic temperature T0 is improved in the strained lasers; the laser with x=0.62 has a T0 of as high as 98 K at 900 μm cavity length. Resonance oscillation frequency fr increases with the InAs content, i.e., the amount of the compressive strain.
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42.55.Px Semiconductor lasers; laser diodes
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

High‐performance planar native‐oxide buried‐mesa index‐guided AlGaAs‐GaAs quantum well heterostructure lasers

S. J. Caracci, F. A. Kish, N. Holonyak, S. A. Maranowski, S. C. Smith, and R. D. Burnham

Appl. Phys. Lett. 61, 321 (1992); http://dx.doi.org/10.1063/1.107924 (3 pages) | Cited 20 times

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High‐performance planar ‘‘buried‐mesa’’ index‐guided AlGaAs‐GaAs quantum well heterostructure (QWH) lasers have been fabricated by oxidation (H2O vapor+N2 carrier gas, 425–525 °C) of a significant thickness of the high composition AlxGa1−xAs upper confining layer (outside the active stripe). The oxide provides excellent current confinement for low‐threshold laser operation and a low refractive index (n∼1.6) for transverse optical confinement and index guiding. Laser diodes with ∼4 μm‐wide active regions exhibit 300 K continuous (cw) laser thresholds of 8 mA, with single longitudinal mode operation to 23 mW/facet, and maximum output powers of 45 mW/facet (uncoated). Devices fabricated on a lower confinement AlxGa1−xAs‐GaAs QWH crystal (x≲0.6 instead of x≳0.8) with ∼4 μm‐wide active stripes exhibit 300 K cw thresholds of 9 mA and total external differential quantum efficiencies of 66%. Peak output powers ≳80 mW/facet (uncoated) with linear L‐I characteristics over the entire operating range are observed. In limited ‘‘lifetest’’ these laser diodes have been operated ≳500 h without significant degradation.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation
81.65.-b Surface treatments

Measurement of elastic relaxation in cross‐sectional transmission electron microscopy of GexSi1−x/Si strained‐layer superlattices

X. F. Duan

Appl. Phys. Lett. 61, 324 (1992); http://dx.doi.org/10.1063/1.107925 (3 pages) | Cited 10 times

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Two types of relaxation occur in the cross‐sectional transmission electron microscopy samples of the GexSi1−x/Si strained‐layer superlattices (SLS) by large‐angle convergent‐beam electron diffraction (LACBED) and imaging technique which gives a good LACBED pattern superimposed on a high spatial resolution shadow image of the SLS. One type of relaxation occurs between the Si and the GeSi layers. It is negligible in the convergent‐beam electron diffraction (CBED) case for the larger value of the ratio of the sample thickness to the SLS wavelength. Another type occurs between the superlattice as an average crystal and the Si substrate. The relaxation of the SLS can be measured by the shift of the Kikuchi line in the SLS from that in the Si substrate.
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68.60.Bs Mechanical and acoustical properties
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination

Observation of interstitial carbon in heavily carbon‐doped GaAs

G. E. Höfler and K. C. Hsieh

Appl. Phys. Lett. 61, 327 (1992); http://dx.doi.org/10.1063/1.107926 (3 pages) | Cited 29 times

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Nuclear reaction analysis, utilizing the 12C(d, p)13C reaction, in conjunction with Rutherford backscattering spectrometry in the channeling geometry were used to determine the lattice locations of carbon in heavily carbon‐doped GaAs samples with carbon concentrations greater than 5×1019 cm−3. The data unambiguously show that at least 25% of the carbon atoms occupied interstitial sites within the channels of the GaAs crystal. The existence of interstitial carbon is important for practical applications since the atomic diffusivity of interstitial carbon may be different from that observed in GaAs when carbon is only incorporated substitutionally.
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61.72.U- Doping and impurity implantation
61.72.jd Vacancies
61.72.jj Interstitials
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients

Trap‐assisted tunneling in mercury cadmium telluride photodiodes

A. Unikovsky and Y. Nemirovsky

Appl. Phys. Lett. 61, 330 (1992); http://dx.doi.org/10.1063/1.107927 (3 pages) | Cited 5 times

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Trap‐assisted tunneling in Hg1−xCdxTe photodiodes (with x≂0.22) is modeled quantitatively. The model takes into consideration two types of deep traps: one type of energy trap is located at Et1≂40 meV (∼Eg/3) and the other type is located at Et2≂75 meV (∼2Eg/3). The density of trapped electrons at Et1∼Eg/3 is relatively high (nt1≂1014 cm−3) and is practically independent of temperature while the density of the trapped electrons at Et2≂2Eg/3 is low (nt2≂1010–1012 cm−3) and increases with temperature. An excellent fit is systematically obtained between the calculated and measured dc dark current characteristics of typical ion implanted n+p photodiodes, in a wide range of reverse bias voltages (0<Vd<−1.5 V) and operating temperatures (30–120 K).
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85.30.De Semiconductor-device characterization, design, and modeling
85.60.Dw Photodiodes; phototransistors; photoresistors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Conversion loss of a YBa2Cu3O7 grain boundary mixer at 20 GHz

Donald P. Butler, Wiyi Yang, Jianglin Wang, Anil Bhandari, and Zeynep Celik‐Butler

Appl. Phys. Lett. 61, 333 (1992); http://dx.doi.org/10.1063/1.107928 (3 pages) | Cited 9 times

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We have measured the conversion gain of a YBa2Cu3O7 annealed grain boundary microbridge mixer by operating the device as a lower side‐band down‐converter from an 18.5 GHz radio frequency to a 1.5 GHz intermediate frequency under the action of a 20.0 GHz local oscillator. We have found the conversion gain to be relatively independent of bias up to a current density which marks the onset of the flux flow resistance. Above the onset of flux flow resistance, the gain decreased dramatically. A maximum conversion gain of −8±4 dB was measured at 25 K. The mixer was operated with a local oscillator power of only −60 dBm. The results demonstrate that high Tc superconductor mixers are capable of delivering comparable conversion gains to Schottky diode mixers while requiring substantially lower power local oscillators.
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85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices
84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors
74.50.+r Tunneling phenomena; Josephson effects
74.70.-b Superconducting materials other than cuprates

Sub‐μm linewidth input coils for low Tc integrated thin‐film dc superconducting quantum interference devices

M. B. Ketchen, K. G. Stawiasz, D. J. Pearson, T. A. Brunner, C.‐K. Hu, M. A. Jaso, M. P. Manny, A. A. Parsons, and K. J. Stein

Appl. Phys. Lett. 61, 336 (1992); http://dx.doi.org/10.1063/1.107929 (3 pages) | Cited 4 times

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We have, for the first time, demonstrated integrated dc superconducting quantum interference devices (SQUIDs) with input coils of linewidth down to 0.5 μm. The SQUID inductance L consists of a single octagonal washer or two or four such washers configured in parallel. The input coil of inductance Li, which couples to L with a mutual inductance of Mi, consists of fine‐line octagonal spiral(s) fabricated in close proximity to the washer(s). For a two‐washer SQUID with twin 80‐turn, 0.5 μm spirals, Li=2.5 μH, Mi=12.7 nH, L=109 pH, and the coupling constant k2=0.85. This entire device occupies an area of less than 0.2 mm2.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)

Electron‐phonon decoupling in the photoresponse of YBaCuO granular films at low temperature

J.‐P. Maneval, F. Chibane, and R. W. Bland

Appl. Phys. Lett. 61, 339 (1992); http://dx.doi.org/10.1063/1.107930 (3 pages) | Cited 7 times

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Granular YBaCuO films in their current‐induced dissipative state were exposed to light pulses of small fluence and the decay of the photoresistance was observed on the nanosecond time scale in the range 1 K<T<35 K. The response appears bolometric down to 10 K. Below, we resolve a second decay rate having a temperature dependence characteristic of the electron‐phonon interaction. Using the known lattice specific heat as a reference, we deduce the Sommerfeld coefficient (γ=2.5 mJ/K2 mol) of the electronic specific heat.
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74.25.N- Response to electromagnetic fields
74.70.-b Superconducting materials other than cuprates
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
74.78.-w Superconducting films and low-dimensional structures

Effect of thermal noise on Shapiro steps in high‐Tc Josephson weak links

R. L. Kautz, R. H. Ono, and C. D. Reintsema

Appl. Phys. Lett. 61, 342 (1992); http://dx.doi.org/10.1063/1.107931 (3 pages) | Cited 12 times

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The amplitudes of Shapiro steps are measured at temperatures up to 77 K for a superconductor‐normal metal‐superconductor Josephson weak link fabricated from YBa2Cu3O7−δ with a Ag‐Au alloy bridge. The step amplitudes are found to be in agreement with calculations based on the resistively shunted‐junction model when the Johnson noise of the junction resistance is included.
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74.50.+r Tunneling phenomena; Josephson effects
74.40.-n Fluctuation phenomena
74.70.-b Superconducting materials other than cuprates

Optical anisotropy of YBa2Cu3O7−δ films on NdGaO3(001) substrates: A comparison with single domain crystals

A. Zibold, K. Widder, H. P. Geserich, T. Scherer, P. Marienhoff, M. Neuhaus, W. Jutzi, A. Erb, and G. Müller‐Vogt

Appl. Phys. Lett. 61, 345 (1992); http://dx.doi.org/10.1063/1.107932 (3 pages) | Cited 9 times

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We have investigated the spectral reflectance of thin YBa2Cu3O7−δ films deposited on twin‐free NdGaO3(001) substrates. Using polarized light in the spectral range between 50 meV and 6 eV, we found a significant a‐b anisotropy near the plasma edge. On the basis of a Lorentz–Drude model we have calculated the tensor components of the dielectric function parallel to the a and to the b axis, respectively. The obtained results are compared with the a‐b anisotropy of single domain crystals.
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78.66.-w Optical properties of specific thin films
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures

On‐axis dc magnetron sputtering of large area high quality YBa2Cu3O7 superconducting thin films

Y. Z. Zhang, L. Li, Y. Y. Zhao, B. R. Zhao, J. W. Li, J. R. Sun, Q. X. Su, and P. Xu

Appl. Phys. Lett. 61, 348 (1992); http://dx.doi.org/10.1063/1.107933 (3 pages) | Cited 6 times

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It is demonstrated by our experiment that using the in situ dc magnetron sputtering method, it is possible to prepare high quality YBa2Cu3O7 (YBCO) thin films with substrates facing the region of plasma ring. The effect of oxygen resputtering can be greatly reduced with a high argon‐oxygen working gas ratio and a large target to substrate distance. It is shown that high quality YBCO thin films of more than 60 mm in diameter, that is about the same size of the diameter of the YBCO target, can be prepared with this process. The thin films were characterized by x‐ray diffractometry, and the critical temperatures were determined by both resistive and ac susceptibility techniques.
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81.15.Cd Deposition by sputtering
74.70.-b Superconducting materials other than cuprates

Metalorganic deposition of high critical current thin films in the Bi‐Sr‐Ca‐Cu‐O system on {100} LaAlO3 substrates

S. J. Golden, F. F. Lange, D. R. Clarke, L. D. Chang, and C. T. Necker

Appl. Phys. Lett. 61, 351 (1992); http://dx.doi.org/10.1063/1.107934 (3 pages) | Cited 6 times

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Superconducting thin films of the two Cu‐layer phase in the Pb‐doped Bi‐Sr‐Ca‐Cu‐O system have been fabricated on {100} LaAlO3 single crystals by the metalorganic deposition from ethyl hexanoate precursors. Thin films given heat treatments in air at 850–860 °C had resistive transitions with a Tc of 86–89 K. The zero‐field transport critical current densities were in the range of 2–4×105 A/cm−2 at 77 K and 106 A cm−2 at 45 K in 200–300‐nm‐thick films. In contrast to c‐axis oriented films grown on {100} MgO, x‐ray pole figures show that the films grown on {100} LaAlO3 are epitaxial, a result confirmed by electron channeling patterns.
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81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
74.70.-b Superconducting materials other than cuprates

Magnetic coupling in amorphous Fe80−xRxB12Si8(R=Er, Gd) alloys

R. Krishnan, H. Lassri, and R. J. Radwanski

Appl. Phys. Lett. 61, 354 (1992); http://dx.doi.org/10.1063/1.107935 (3 pages) | Cited 6 times

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We have prepared amorphous Fe‐Er‐B‐Si and Fe‐Gd‐B‐Si alloys and magnetization studies in fields up to 35 T at 4.2 K have been carried out on some selected samples. The results have been analyzed on the existing model proposed by Verhoef et al. for crystalline Fe and Co compounds with rare earths. The magnetic moments of Fe, Er, and Gd, as well as other parameters such as the intersublattice molecular‐field coefficient (nRT), the strength of the exchange interaction etc., have been determined.
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75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Gg Ferrimagnetics
75.30.Et Exchange and superexchange interactions

Tunneling stabilized magnetic force microscopy of BaFe12O19 with a thin film tip

A. Wadas, H. J. Hug, and H.‐J. Güntherodt

Appl. Phys. Lett. 61, 357 (1992); http://dx.doi.org/10.1063/1.107942 (3 pages) | Cited 6 times

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Magnetic domains of BaFe12O19 have been imagined with a scanning tunneling microscope having a flexible, magnetic tip. We have found that Co thin films evaporated on a silicon tip, integrated with a cantilever, can give high lateral resolution, below 50 nm. Therefore, we have been able to image domains and domain walls simultaneously. We have observed domains of 1.9 μm width and domain walls of 270 nm width. We explained the data using existing models.
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75.50.Vv High coercivity materials
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
75.80.+q Magnetomechanical effects, magnetostriction

Importance of the high‐velocity projectile‐z3 term in modified Bethe–Bloch stopping power theory

L. E. Porter

Appl. Phys. Lett. 61, 360 (1992); http://dx.doi.org/10.1063/1.107943 (3 pages) | Cited 4 times

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Modified Bethe–Bloch theory of stopping power provides for inclusion of several parameters in the Bethe–Bloch formula. These parameters include the target mean excitation energy and those associated with target shell corections, with the low‐velocity projectile‐z3 (Barkas effect) term, and with an effective charge factor. Fits of stopping power measurements permit extraction of one or two (and sometimes three) parameter values while the remaining parameters are assigned fixed values based on other studies. Omission of one or more of the required correction terms or factors induces distortions in the values of the extracted parameters. A recent development has been omission of the (parameter independent) high‐velocity Barkas effect term in an analysis where projectile energies were sufficiently high to necessitate inclusion of this term. The importance of incorporating all pertinent terms and factors into the modified Bethe–Bloch formula is strenuously emphasized.
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61.85.+p Channeling phenomena (blocking, energy loss, etc.)

Theory of stability in a nonlinear resistive network

T. Uenoyama, L. Esaki, and H. Kotera

Appl. Phys. Lett. 61, 363 (1992); http://dx.doi.org/10.1063/1.107912 (3 pages) | Cited 2 times

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In a nonlinear resistive network, Kirchhoff’s laws and branch equations generally give several solutions as operating points. We have studied the condition of the stability of the solutions, taking into account the curvature of the total power in voltage‐current space. Since the power of each element is expressed by integration over the voltage and current as independent functions, this new expression makes a geometrical representation of the total power. It is shown that the differentiable and minimum points correspond to the physical operating points of the network.
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84.30.Bv Circuit theory
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)

Partial pressure gradients due to temperature gradients in a mixture of reactive gases

O. Porat and I. Riess

Appl. Phys. Lett. 61, 366 (1992); http://dx.doi.org/10.1063/1.107913 (3 pages) | Cited 1 time

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Partial pressure gradients due to temperature gradients in a mixture of reactive gases, limit the possible use of sensors. Problems arise when a partial pressure sensor is subjected to a temperature, different from that of the sample. A model is proposed that allows the calculation of the partial pressure distributions in a temperature gradient. Experiments conducted using O2, H2, and H2O in Ar confirm the predictions. It is shown how to relate the sensor’s reading to the parameter of interest. It is also concluded that in certain cases it is advisable to deliberately add a reactive gas, as this facilitates the interpretation of the measurements.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
82.60.Hc Chemical equilibria and equilibrium constants
82.80.-d Chemical analysis and related physical methods of analysis
51.30.+i Thermodynamic properties, equations of state
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