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24 Jan 1994

Volume 64, Issue 4, pp. 397-529

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Strain distribution in InP/InGaAs superlattice structure determined by high resolution x‐ray diffraction

A. Krost, J. Böhrer, H. Roehle, and G. Bauer

Appl. Phys. Lett. 64, 469 (1994); http://dx.doi.org/10.1063/1.111132 (3 pages) | Cited 7 times

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Interfacial strain distribution in a short period InP/InGaAs superlattice structure is evaluated by means of high resolution x‐ray diffraction. The diffraction pattern of the structure allows an unambiguous determination of interfacial strain distribution. From the numerical calculation, positively strained interfacial monolayers at the InP→InGaAs and negatively strained interfacial monolayers at the InGaAs→InP interfaces had to be introduced in order to reproduce the experimental data. At the InP→InGaAs interfaces a group V exchange reaction leading to a positively strained InAs or InAs1−xP interfacial layer is compatible with the simulation. At the InGaAs→InP interfaces negatively strained ternary or quaternary InGaAsyP1−y meet these requirements. The results are consistent with low temperature calorimetric absorption measurements which exhibit a wide band gap InGaAsP‐like absorption feature at 1.48 eV beyond the InP energy gap.
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68.55.-a Thin film structure and morphology
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.05.cf X-ray scattering (including small-angle scattering)
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.

GaAs/AlAs trench‐buried quantum wires with nearly rectangular cross sections grown by metalorganic chemical vapor deposition on V‐grooved substrates

T. Sogawa, S. Ando, and H. Kanbe

Appl. Phys. Lett. 64, 472 (1994); http://dx.doi.org/10.1063/1.111133 (3 pages) | Cited 9 times

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GaAs trench‐buried quantum wires were fabricated by using U‐grooved AlAs trenches grown on V‐grooved (001) substrates. These trench structures with vertical (110) sidewalls were formed by the faceting of (110) planes, and lateral growth of these planes reduced the trench width to less than 20 nm. A cross‐sectional scanning electron microscope image of these trench‐buried structures showed GaAs wires about 20 nm wide and 20 nm thick. The growth of these wires is enhanced by the capture of Ga species into the trenches. Blueshifts and strong anisotropy of photoluminescence confirm two‐dimensional quantum confinement.
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68.55.-a Thin film structure and morphology
78.55.Cr III-V semiconductors

Low dark current dual band infrared photodetector using thin AlAs barriers and Γ‐X mixed intersubband transition in GaAs quantum wells

H. C. Liu, P. H. Wilson, M. Lamm, A. G. Steele, Z. R. Wasilewski, Jianmeng Li, M. Buchanan, and J. G. Simmons

Appl. Phys. Lett. 64, 475 (1994); http://dx.doi.org/10.1063/1.111134 (3 pages) | Cited 15 times

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A low dark current dual band quantum well infrared photodetector is demonstrated by adding thin AlAs barriers to the usual detector structure, which consists of Si‐doped GaAs wells separated by thick AlGaAs barriers. The advantages of adding the thin AlAs barriers to clad the quantum wells are that (a) the detector displays a low dark current and (b) intersubband photocurrents result from transitions from both the Γ ground to the first excited state, and from the Γ ground to a mixed Γ‐X excited state because the X‐valley band edge forms a well in AlAs and intrinsic Γ‐X mixing occurs. The spectral peaks of these two transitions, which occur at 8.5 and 5.5 μm in our test structure, can be varied by changing device parameters during growth.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.Pz Photoconduction and photovoltaic effects

Strained InGaAs/AlGaAs quantum well infrared detectors at 4.5 μm

A. Fiore, E. Rosencher, P. Bois, J. Nagle, and N. Laurent

Appl. Phys. Lett. 64, 478 (1994); http://dx.doi.org/10.1063/1.111135 (3 pages) | Cited 17 times

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We demonstrate midinfrared photodetection at λ=4.5 μm in a multi‐quantum well detector using a strained InGaAs/AlGaAs alloy grown on a GaAs substrate. The detector shows very low dark current of a few pA, a peak unpolarized light responsivity R=12 mA/W for an external 45° angle of incidence, and a background‐limited detectivity D∗BL=4×1010 cm Hz1/2/W at temperatures up to 95 K in the same conditions. This opens the way to high performance 3–5 and 8–12 μm GaAs‐based multispectral detectors
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85.60.Gz Photodetectors (including infrared and CCD detectors)
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Adsorbate effects on photoluminescence and electrical conductivity of porous silicon

Moshe Ben‐Chorin, Andreas Kux, and Israel Schechter

Appl. Phys. Lett. 64, 481 (1994); http://dx.doi.org/10.1063/1.111136 (3 pages) | Cited 85 times

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Porous silicon (p type) has been exposed to several chemical vapors at various partial pressures. The quenching of the photoluminescence by the adsorbates has been quantified and correlation to the electrical conductivity of the porous silicon sample has been studied. Some gases, e.g., water and benzene, have a small effect on the photoluminescence and on the conductivity, while others, e.g., methanol, reduce the photoluminescence by a factor of 2 and increase the conductivity by four orders of magnitude. This is accompanied with a qualitative change in the current‐voltage characteristics. These changes have been found to be reversible and the temporal behavior of the system has been investigated.
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78.55.Hx Other solid inorganic materials
72.80.-r Conductivity of specific materials

Growth mode evolution during homoepitaxy of GaAs (001)

M. D. Johnson, J. Sudijono, A. W. Hunt, and B. G. Orr

Appl. Phys. Lett. 64, 484 (1994); http://dx.doi.org/10.1063/1.111137 (3 pages) | Cited 16 times

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Scanning tunneling microscopy studies have been performed on GaAs homoepitaxial films grown by molecular‐beam epitaxy. After an initial transient regime, indicated by reflection high‐energy electron diffraction oscillations, the system evolves to a dynamical steady state. This state is characterized by a constant step density and as such the growth mode can be termed generalized step flow.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Fluctuating deep‐level trap occupancy model for Hooge’s 1/f noise parameter for semiconductor resistors

Patrick A. Folkes

Appl. Phys. Lett. 64, 487 (1994); http://dx.doi.org/10.1063/1.111138 (3 pages)

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A theoretical expression for Hooge’s 1/f noise parameter α, for a Schottky barrier field‐effect transistor, which has been biased at a small drain‐source voltage (a gate‐controlled semiconductor resistor), has been derived. The theory is based on the fluctuating occupancy of deep level traps in the depletion region. The theory explains the large variations in the observed values of Hooge’s parameter since the derived expression shows that α varies approximately as n−7/2, where n is the electron density, and that α is sensitive to the trap concentration, the gate (or semiconductor surface) potential, the thickness of the semiconductor conducting layer, and the low‐field electron mobility‐depletion depth profile. Detailed experimental characterization of a semiconductor resistor has been carried out resulting in the accurate determination of α over a range of the applied gate voltage, Vg. We obtain excellent agreement between the theoretical and experimental dependence of α on Vg.
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72.70.+m Noise processes and phenomena
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling

Raman spectroscopic study on the wirelike incorporation of Si dopant atoms on GaAs(001) vicinal surfaces

M. Ramsteiner, J. Wagner, D. Behr, G. Jungk, L. Däweritz, and R. Hey

Appl. Phys. Lett. 64, 490 (1994); http://dx.doi.org/10.1063/1.111139 (3 pages) | Cited 6 times

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Raman scattering by collective electronic excitations from a δ‐doping layer has been used to investigate the ordered incorporation of Si dopant atoms on vicinal GaAs(001) surfaces. In a series of δ‐doped samples grown by molecular beam epitaxy (MBE) under specific conditions the Si dopant atoms were found to be incorporated predominantly on Ga sites, even at a doping concentration as high as 1.8×1013 cm−2. A pronounced polarization asymmetry in the Raman scattering intensity of collective intersubband plasmon‐phonon modes was observed in a sample grown under conditions established by real‐time high‐energy electron diffraction to be favorable for wirelike Si incorporation.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.30.Fs III-V and II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Cross‐sectional scanning tunneling microscopy of doped and undoped AlGaAs/GaAs heterostructures

S. Gwo, K.‐J. Chao, and C. K. Shih

Appl. Phys. Lett. 64, 493 (1994); http://dx.doi.org/10.1063/1.111140 (3 pages) | Cited 8 times

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Scanning tunneling microscopy (STM) was used to study the (NH4)2S‐passivated (110) cross‐sectional surfaces of both doped and undoped Al0.3Ga0.7As/GaAs heterostructures on n+‐substrates. The ex situ (NH4)2S treatment of the cross‐sectional surfaces of heterostructures was found to be very stable against oxidation. STM images showed no appreciable deterioration of surface quality in vacuum after more than 40 days. The spectroscopic results on the undoped epilayer showed diodelike behavior, confirming that an undoped large band gap region can be imaged by STM through carrier injection from the conductive regions.
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68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
68.55.-a Thin film structure and morphology
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.65.-b Surface treatments

Room temperature study of strong lateral quantization effects in InGaAs/InP quantum wires

P. Ils, M. Michel, A. Forchel, I. Gyuro, M. Klenk, and E. Zielinski

Appl. Phys. Lett. 64, 496 (1994); http://dx.doi.org/10.1063/1.111142 (3 pages) | Cited 31 times

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We have fabricated In0.53Ga0.47As/InP quantum wires with lateral widths down to 8 nm by high voltage electron beam lithography and deep wet chemical etching. The wires were studied by photoluminescence spectroscopy at room temperature. Down to the smallest wire widths a clear photoluminescence signal is observed. The decrease of the luminescence yield with decreasing wire width indicates that no significant damage has been induced at the sidewalls of the wires during the fabrication process. For wires with widths below about 60 nm a blue shift of the photoluminescence energy is observed, which reaches up to 73 meV for 8 nm wide wires. The experimentally observed width variation of the lateral quantization can be modeled quantitatively by using the measured width of the wires and standard band parameters.
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78.55.Cr III-V semiconductors
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
81.65.-b Surface treatments
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Maskless InP wire formation on planar GaAs substrates

J. Ahopelto, H. Lezec, Y. Ochiai, A. Usui, and H. Sakaki

Appl. Phys. Lett. 64, 499 (1994); http://dx.doi.org/10.1063/1.111109 (3 pages) | Cited 7 times

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Maskless growth of InP wires on planar (100)GaAs substrates by hydride vapor phase epitaxy is demonstrated. The selectivity of the growth was achieved by using focused ion beam to modify locally the substrate surface. The nucleation of deposited InP is enhanced on the exposed areas leading to the selectivity. Continuous 200 μm long wires with submicron cross‐sectional dimensions were obtained in a single growth process. Cross‐sectional transmission electron microscope micrographs show that the number of dislocations in the wires is relatively low, indicating the suitability of the present method for fabrication of nanoscale structures, e.g., quantum wires.
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68.55.-a Thin film structure and morphology
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
82.50.Kx Processes caused by X-rays or γ-rays

Effective band‐gap shrinkage in GaAs

E. S. Harmon, M. R. Melloch, and M. S. Lundstrom

Appl. Phys. Lett. 64, 502 (1994); http://dx.doi.org/10.1063/1.111110 (3 pages) | Cited 12 times

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Electrical measurements of the equilibrium np product (n2ie) in heavily doped n‐ and p‐GaAs were performed. The n2ieD product (where D is the diffusivity) was measured by fitting the collector current‐voltage characteristic of a homojunction bipolar transistor to an ideal diode equation modified to account for transport in thin base transistors. The n2ie product was then extracted from n2ieD by utilizing diffusivity results obtained with the zero‐field time‐of‐flight technique. Our results show significant effective band‐gap shrinkage in heavily doped p‐GaAs, and very little effective band‐gap shrinkage in heavily doped n‐GaAs. At extremely heavy dopings, an effective band‐gap widening is observed for both n‐ and p‐GaAs and is attributed to the effects of degeneracy.
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71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds
71.55.Eq III-V semiconductors
85.30.Pq Bipolar transistors
73.61.Ey III-V semiconductors

Design criteria for structurally stable, highly strained multiple quantum well devices

D. C. Houghton, M. Davies, and M. Dion

Appl. Phys. Lett. 64, 505 (1994); http://dx.doi.org/10.1063/1.111111 (3 pages) | Cited 20 times

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Strain compensation allows the synthesis of infinitely thick heterostructures with many highly strained quantum wells. Design criteria are given for optimized strain and thickness parameters in several device geometries. Strain compensation, using alternating layers of opposite strain, is quantitatively treated using an energy balance analysis. The upper bound to stability for strained multiple quantum wells with and without strain compensation is defined for geometries typically used in optoelectronic devices. Highly metastable structures (composed of many layers of high strain and/or thickness) require low epitaxy temperatures to avoid strain relaxation during growth of individual strained layers, prior to their stabilization in a strain compensated structure.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.55.-a Thin film structure and morphology

Shallow oxygen‐related donors in bonded and etchback silicon on insulator structures

W. L. Warren, D. M. Fleetwood, J. R. Schwank, M. R. Shaneyfelt, P. S. Winokur, R. A. B. Devine, and W. P. Maszara

Appl. Phys. Lett. 64, 508 (1994); http://dx.doi.org/10.1063/1.111112 (3 pages) | Cited 4 times

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Using electron paramagnetic resonance we have been able to identify a new oxygen‐related donor defect in the Si substrate of bonded and etchback silicon‐on‐insulator structures. This axially symmetric donor is preferentially aligned along the [100] direction, and resides close to the Si/SiO2 interface. It is tentatively suggested that the donors result from the nonoxidizing anneal received by the wafers during the bonding process.
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61.72.Cc Kinetics of defect formation and annealing
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
71.55.Cn Elemental semiconductors

Effect of proton irradiation on the critical current and resistance of high Tc grain boundary Josephson junctions

E. M. Jackson, B. D. Weaver, and G. P. Summers

Appl. Phys. Lett. 64, 511 (1994); http://dx.doi.org/10.1063/1.111089 (3 pages) | Cited 5 times

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We have investigated the effects of defects on the critical current and resistance of high Tc grain boundary Josephson junctions using irradiation with 2‐MeV protons. Radiation‐induced defects cause the critical current (Ic) to decrease and the shunt resistance (R) to increase such that IcR∝1/R. The data are consistent with a tunneling barrier height increasing with fluence.
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74.50.+r Tunneling phenomena; Josephson effects
74.81.Bd Granular, melt-textured, amorphous, and composite superconductors
74.72.-h Cuprate superconductors
61.80.Jh Ion radiation effects

Four‐channel YBa2Cu3O7−y dc SQUID magnetometer for biomagnetic measurements

S. Tanaka, H. Itozaki, H. Toyoda, N. Harada, A. Adachi, K. Okajima, H. Kado, and T. Nagaishi

Appl. Phys. Lett. 64, 514 (1994); http://dx.doi.org/10.1063/1.111090 (3 pages) | Cited 15 times

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A four‐channel YBa2Cu3O7−y thin film dc SQUID magnetometer was fabricated. Biomagnetic measurements were performed by using the four‐channel system at 77 K in a magnetically shielded room. We have successfully measured four‐channel magnetocardiac signals clearly in real‐time mode. The best magnetic field resolution of the four SQUIDs was 370 fT/Hz1/2 at 10 Hz and 200 fT/Hz1/2 in the white noise region.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
87.50.C- Static and low-frequency electric and magnetic fields effects
87.80.-y Biophysical techniques (research methods)

High Tc Josephson junctions combining a grain boundary and local strain, using NdGaO3 bicrystal substrates

P. G. Quincey

Appl. Phys. Lett. 64, 517 (1994); http://dx.doi.org/10.1063/1.111091 (3 pages) | Cited 12 times

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The bicrystal substrate approach to high Tc Josephson junctions has previously used substrates with cubic (isotropic) structure. NdGaO3, which has orthorhombic structure, has excellent lattice match to YBa2Cu3O7−x and good dielectric properties. When bicrystals are made with NdGaO3 in the usual (110) orientation, the anisotropy means that there will be thermally induced local strain at the grain boundary in any overlaid film. Several junctions have been made with this novel variation on the bicrystal technique, showing values of IcRN around 400 μV at 77 K.  
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74.81.Bd Granular, melt-textured, amorphous, and composite superconductors
74.50.+r Tunneling phenomena; Josephson effects
74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors

Thermal instability, magnetic field shielding and trapping in single‐grain YBa2Cu3O7−δ bulk materials

L. Gao, Y. Y. Xue, R. L. Meng, and C. W. Chu

Appl. Phys. Lett. 64, 520 (1994); http://dx.doi.org/10.1063/1.111092 (3 pages) | Cited 9 times

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We report results on the temperature dependence of the trap field BT and the thermal instability (flux jump) field Hfj in single‐grain YBa2Cu3O7−δ disks. Above 45 K, BT is limited by the critical current density Jc and BT=BT0(1−T/Tc)q with q≊1.67. At 4.2 K, the first flux jump field Hfj of ∼3 T is about an order of magnitude larger than theoretical prediction based on the adiabatic thermal instability model. We also find that the occurrence of large flux avalanches probably causes severe microcracking damages to the superconducting disks.
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74.25.-q Properties of superconductors
84.71.Ba Superconducting magnets; magnetic levitation devices
74.72.-h Cuprate superconductors

Nanometer‐scale lithography on Si surface by decomposition of ferrocene molecules using a scanning tunneling microscope

F. Thibaudau, J. R. Roche, and F. Salvan

Appl. Phys. Lett. 64, 523 (1994); http://dx.doi.org/10.1063/1.111093 (3 pages) | Cited 16 times

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We describe lithography experiments on boron doped Si substrates using the decomposition of ferrocene molecules with a scanning tunneling microscope tip. On the basis of writing conditions we propose that field ionization of the molecules is the key to the writing process and is responsible for the nanometer definition of the pattern edge.  
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
85.40.Hp Lithography, masks and pattern transfer
79.70.+q Field emission, ionization, evaporation, and desorption
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Existence of persistent photoconductivity in C70

A. Hamed, H. Rasmussen, and P. H. Hor

Appl. Phys. Lett. 64, 526 (1994); http://dx.doi.org/10.1063/1.111094 (3 pages) | Cited 5 times

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We have observed a persistent photoconductivity effect (PPC) in C70 films well above room temperature. The effect, which consists of a metastable increase in dark conductivity caused by brief exposure to light, exhibits characteristics very similar to the PPC previously observed in C60 films. These characteristics include a magnitude of the effect independent of the light exposure temperature, the existence of a PPC even at 520 K, and the inability of subgap illumination to create or quench PPC. A common origin for the PPC in C70 and C60 seems plausible, and may be related to the distortions the fullerene molecules experience when charged.
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72.40.+w Photoconduction and photovoltaic effects
FREE

Erratum: ‘‘Time dependent ballistic electron emission microscopy studies of a Au/(100)GaAs interface with a native oxide diffusion barrier’’ [Appl. Phys. Lett. 62, 2965 (1993)]

A. Alec Talin, Douglas A. A. Ohlberg, R. Stanley Williams, Patrick Sullivan, Ioannis Koutselas, Beth Williams, and Karen L. Kavanagh

Appl. Phys. Lett. 64, 529 (1994); http://dx.doi.org/10.1063/1.111998 (1 page) | Cited 1 time

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Abstract Unavailable
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
73.20.At Surface states, band structure, electron density of states
99.10.Cd Errata
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