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19 Nov 1990

Volume 57, Issue 21, pp. 2169-2273

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As2S3/GaAs, a new amorphous/crystalline heterojunction for the III‐V semiconductors

E. Yablonovitch, T. J. Gmitter, and B. G. Bagley

Appl. Phys. Lett. 57, 2241 (1990); http://dx.doi.org/10.1063/1.104163 (3 pages) | Cited 17 times

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Much of the technology of our era is based on the SiO2/Si amorphous/crystalline heterojunction interface. Now it appears that As2S3/GaAs amorphous/crystalline heterojunctions show some technological promise. We have found that properly prepared As2S3/GaAs interfaces can have reasonably good electronic quality. The interfacial recombination velocity is ≊15 000 cm/s at flat band, which results in a ∼100‐fold reduction of perimeter recombination currents in p‐n junction mesas. This can be important on heterojunction transistor emitter‐base perimeters, solar cell and light‐emitting diode perimeters, and for reducing mirror facet recombination in semiconductor lasers.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.61.Ga II-VI semiconductors
73.20.At Surface states, band structure, electron density of states

Compositional modulation and long‐range ordering in GaP/InP short‐period superlattices grown by gas source molecular beam epitaxy

K. C. Hsieh, J. N. Baillargeon, and K. Y. Cheng

Appl. Phys. Lett. 57, 2244 (1990); http://dx.doi.org/10.1063/1.103903 (3 pages) | Cited 64 times

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Long‐range ordering in a (GaP)2/(InP)2 short‐period superlattice and a Ga0.525In0.475P buffer layer grown on a (001)GaAs substrate by gas source molecular beam epitaxy were studied. Transmission electron microscopy and low‐temperature cathodoluminesence techniques were used to examine the microstructure of the short‐period superlattice and to determine its band‐gap energy. The superlattice layer was found to have a [001] long‐range ordered structure with a band gap narrowing of about 130 meV, while the Ga0.525In0.475P layer had a 37 meV band‐gap narrowing induced by spontaneous long‐range ordering in the [111] direction. The ordered superlattice layer was found to have a growth‐induced lateral periodic modulation of the composition along the [110] direction. Within the modulating bands, which had a 200 Å periodicity, the In composition was found to vary from 42 to 56% while the Ga correspondingly varied between 58 and 44%.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.60.Hk Cathodoluminescence, ionoluminescence
73.61.Ey III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Strain in porous Si formed on a Si (100) substrate

Gang Bai, Kun Ho Kim, and Marc‐A. Nicolet

Appl. Phys. Lett. 57, 2247 (1990); http://dx.doi.org/10.1063/1.103904 (3 pages) | Cited 17 times

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The strain in a porous Si layer formed by anodization of a crystalline p+‐Si(100) wafer in a HF electrolyte was measured by double‐crystal x‐ray diffractometry. The perpendicular strain in the as‐formed porous Si layer is ∼10−3. The parallel strain is not measurable (<10−4). Upon annealing in vacuum from 200–800 °C, at elevated temperature, the perpendicular strain decreases while the parallel strain remains zero. Subsequently, the perpendicular strain of the annealed sample increases by amounts that depend on the ambient. The observed changes of strain in porous Si layers are explained as being mainly caused by modification of the stress in the native oxide layer due to desorption and absorption of gas. We propose that the strain in porous Si is the net result of stress induced by surface tension, oxide formation, and exchange of gas between the oxide and ambient.
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68.35.Gy Mechanical properties; surface strains
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.40.Lm Deformation, plasticity, and creep

Dissimilarity between thermal oxide and buried oxide fabricated by implantation of oxygen on Si revealed by etch rates in HF

K. Vanheusden and A. Stesmans

Appl. Phys. Lett. 57, 2250 (1990); http://dx.doi.org/10.1063/1.103905 (3 pages) | Cited 6 times

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A comparative study of diluted HF etch rates was performed on thermally grown oxide (1120 °C; O2 pressure ≊1.1 atm) and buried oxide layers [formed by implanting n‐and p‐type (100)Si maintained at ≊600 °C with 150–200 keV O+ ions to a dose of ≊1.8×1018 cm−2, and subsequent annealing at 1250–1325 °C]. From accurate mechanical thickness measurements, a difference in etch rate between thermally grown and buried oxide is observed. This is direct evidence for a structural and/or stoichiometrical difference between both oxides. Additionally, plots of the etch rate as a function of oxide thickness reveal detailed information on the local structure of the oxide layers.
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81.05.Kf Glasses (including metallic glasses)
81.65.-b Surface treatments
68.55.-a Thin film structure and morphology

High‐energy (56 MeV) oxygen implantation in Si, GaAs, and InP

S. J. Pearton, B. Jalali, J. M. Poate, J. D. Fox, K. W. Kemper, C. W. Magee, and K. S. Jones

Appl. Phys. Lett. 57, 2253 (1990); http://dx.doi.org/10.1063/1.103906 (3 pages) | Cited 2 times

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The depth profiles measured by secondary‐ion mass spectrometry of 56 MeV oxygen ions implanted into Si, GaAs, and InP are reported. Most of the oxygen is contained within a sharp (full width at half maximum ∼2 μm) non‐Gaussian profile centered at ∼31 μm in GaAs, ∼36 μm in InP, and ∼46 μm in Si, with the distribution skewed towards greater depths. The experimental projected ranges appear to be 10% larger than theoretical predictions. Changes in the electrical, optical, and structural properties of the material were measured by transmission electron microscopy (TEM), photoluminescence, and spreading resistance profiling. In the as‐implanted Si, the maximum perturbation in the electrical properties occurs at ∼37 μm. No defects are visible by TEM in any of the as‐implanted semiconductors for oxygen ion doses of 1.35×1015 cm−2 but the photoluminescent intensity in GaAs and InP is reduced by more than an order of magnitude as a result of this type of implantation.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.61.Ey III-V semiconductors
61.72.uf Ge and Si
61.72.U- Doping and impurity implantation

p‐type doping of gallium antimonide grown by molecular beam epitaxy using silicon

T. M. Rossi, D. A. Collins, D. H. Chow, and T. C. McGill

Appl. Phys. Lett. 57, 2256 (1990); http://dx.doi.org/10.1063/1.103907 (3 pages) | Cited 9 times

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We report the first effective p‐type doping of molecular beam epitaxy (MBE) grown GaSb using silicon. The samples were grown by molecular beam epitaxy and characterized by Hall‐effect measurements and photoluminescence. Room‐temperature hole concentrations ranging from 4.0×1015 to 4.3×1018 cm−3 were obtained. Photoluminescence (PL) spectra undergo considerable broadening with increasing doping concentration, consistent with an impurity banding picture. Furthermore, the MBE‐grown samples display only one of the two PL features found in a melt‐grown substrate and no other satellites, suggesting higher material purity. This may be a direct benefit from the use of an antimony cracker, ultrahigh vacuum conditions, and high‐purity elemental sources. The short‐period strained‐layer superlattice buffering scheme employed may have also contributed to better structural quality.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors

Localized two‐dimensional electron gas formation by focused Si ion beam implantation into GaAs/AlGaAs heterostructures

S. Sasa, M. S. Miller, Y. J. Li, Z. Xu, K. Ensslin, and P. M. Petroff

Appl. Phys. Lett. 57, 2259 (1990); http://dx.doi.org/10.1063/1.103908 (3 pages) | Cited 12 times

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We have demonstrated the localized formation of a two‐dimensional electron gas (2DEG) using focused Si ion beam implantation (100 keV) into undoped GaAs/AlGaAs heterostructures. We found that to achieve a good‐quality 2DEG without also forming a 3DEG it is essential to use a double instead of a single interface heterostructure. The low‐temperature mobility of the 2DEG was as high as 1.0×104 cm2/V s at a carrier concentration of 1×1012 cm−2. This 2DEG mobility in the double heterostructure was a factor of 3 larger than the 2DEG mobility in the single heterostructures.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Dn Low-field transport and mobility; piezoresistance
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
FREE

Erratum: Correlations between the interfacial chemistry and current‐voltage behavior of n‐GaAs/liquid junctions [Appl. Phys. Lett. 57, 1242 (1990)]

Bruce J. Tufts, Louis G. Casagrande, Nathan S. Lewis, and Frank J. Grunthaner

Appl. Phys. Lett. 57, 2262 (1990); http://dx.doi.org/10.1063/1.104288 (3 pages) | Cited 3 times

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Abstract Unavailable
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73.30.+y Surface double layers, Schottky barriers, and work functions
72.40.+w Photoconduction and photovoltaic effects
68.08.-p Liquid-solid interfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
99.10.Cd Errata

Recovery of original superconducting properties in ion‐irradiated Y1Ba2Cu3O7−x thin films

S. Vadlamannati, P. England, N. G. Stoffel, R. Ramesh, T. S. Ravi, D. M. Hwang, A. Findikoglu, Q. Li, T. Venkatesan, and W. L. McLean

Appl. Phys. Lett. 57, 2265 (1990); http://dx.doi.org/10.1063/1.104164 (3 pages) | Cited 8 times

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The changes in the superconducting properties of in situ pulsed laser deposited Y1Ba2Cu3O7−x thin films caused by irradiation with 200 keV He+ ions are due to both oxygen loss as well as oxygen and cationic displacements induced by the irradiation. This is demonstrated by a study of the recovery of these defects by plasma oxidation and relatively low temperature (∼600 °C) annealing in oxygen. Plasma oxidation of films irradiated to low fluences enables the replacement of oxygen atoms in the lattice, leading to a substantial recovery of Tc0, Jc, and normal state resistivity. Irradiation‐induced oxygen and cationic displacements and other microscopic defects can be further annealed out at relatively low temperatures leading to an almost full recovery of Tc0, Jc, and normal state resistivity. A transmission electron microscope study of irradiated films shows evidence that they are structurally disordered.
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74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.78.-w Superconducting films and low-dimensional structures
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.70.-b Superconducting materials other than cuprates

Microstructure of epitaxial YBa2Cu3O7−x thin films grown on LaAlO3 (001)

Yong‐Fen Hsieh, Michael P. Siegal, Robert Hull, and Julia M. Phillips

Appl. Phys. Lett. 57, 2268 (1990); http://dx.doi.org/10.1063/1.104165 (3 pages) | Cited 14 times

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We report a microstructural investigation of the epitaxial growth of YBa2Cu3O7−x (YBCO) thin films on LaAlO3 (001) substrates using transmission electron microscopy (TEM). Epitaxial films grow with two distinct modes: c epitaxy (YBCO) single crystal with the c axis normal to the surface) and a epitaxy (YBCO) single crystal with the c axis in the interfacial plane), where c epitaxy is the dominant mode grown in all samples 35–200 nm thick. In 35 nm YBCO films annealed at 850 °C, 97±1% of the surface area is covered by c epitaxy with embedded anisotropic a‐epitaxial grains. Quantitative analysis reveals the effect of film thickness and annealing temperature on the density, grain sizes, areal coverages, and anisotropic growth of a epitaxy.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Direct nanometer scale patterning of SiO2 with electron beam irradiation through a sacrificial layer

D. R. Allee and A. N. Broers

Appl. Phys. Lett. 57, 2271 (1990); http://dx.doi.org/10.1063/1.103909 (3 pages) | Cited 34 times

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Nanometer scale patterns have been fabricated in SiO2 by electron beam exposure through a sacrificial layer. Although the process of patterning SiO2 with direct electron beam irradiation was discovered over two decades ago, the smallest feature size previously achieved was 0.6 μm because finely focused electron beams form a contamination layer on the substrate blocking the subsequent development of the oxide with HF wet etches. Exposing through a sacrificial layer, the contamination is readily removed with the stripping of the sacrificial layer. Using high energy electrons (300 keV) to minimize forward scattering of the beam, arrays of lines with a period down to 21 nm have been fabricated in the SiO2.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.65.-b Surface treatments
61.80.Fe Electron and positron radiation effects
85.40.Hp Lithography, masks and pattern transfer
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