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11 Nov 1991

Volume 59, Issue 20, pp. 2483-2617

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Calculated performance of p+n InP solar cells with In0.52Al0.48As window layers

R. K. Jain and G. A. Landis

Appl. Phys. Lett. 59, 2555 (1991); http://dx.doi.org/10.1063/1.105951 (3 pages) | Cited 6 times

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We have calculated the performance of indium phosphide solar cells with lattice matched wide band‐gap In0.52Al0.48As window layers using the PC‐1D computer code. The conversion efficiency of p+n InP solar cells is improved significantly by the window layer. No improvement is seen for n+p structures. The improvement in InP cell efficiency was studied as a function of In0.52Al0.48As layer thickness. The use of the window layer improves both the open circuit voltage and short circuit current. For a typical In0.52Al0.48As window layer thickness of 20 nm, the cell efficiency improves in excess of 27% to a value of 18.74%.
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85.60.-q Optoelectronic devices
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Pz Photoconduction and photovoltaic effects

Large nonlinear phase shifts in low‐loss AlxGa1−xAs waveguides near half‐gap

S. T. Ho, C. E. Soccolich, M. N. Islam, W. S. Hobson, A. F. J. Levi, and R. E. Slusher

Appl. Phys. Lett. 59, 2558 (1991); http://dx.doi.org/10.1063/1.105952 (3 pages) | Cited 25 times

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We study the instantaneous nonlinear index change in Al0.2Ga0.8As waveguides below the two‐photon absorption edge and find π phase shifts with 80 pJ, 0.4 ps pulses at wavelengths near 1.6 μm. These large phase shifts are obtained with less than 1 dB of loss from multiphoton absorption. Our results indicate that AlGaAs waveguides, which have a mature fabrication technology, can be used as compact nonlinear elements in switching and quantum optics applications in the near‐infrared. Further optimization of the waveguide geometry should result in useful nonlinear phase shifts and low losses for pulse energies approaching a picojoule.
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42.79.Gn Optical waveguides and couplers
42.60.Fc Modulation, tuning, and mode locking
42.79.Hp Optical processors, correlators, and modulators
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

Detection of the EL2 metastability by x‐ray rocking‐curve measurements at low temperatures

G. Kowalski and M. Leszczynski

Appl. Phys. Lett. 59, 2561 (1991); http://dx.doi.org/10.1063/1.105953 (3 pages) | Cited 8 times

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X‐ray experiments are usually seen as a tool for studying large lattice imperfections. We present for the first time experimental evidence obtained from x‐ray measurements that metastable behavior of the EL2 defect in semi‐insulating GaAs can be connected with crystal lattice relaxation. New unexpected results showing change of the lattice state while cooling semi‐insulating GaAs samples in darkness are also reported.
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61.72.J- Point defects and defect clusters
61.05.C- X-ray diffraction and scattering

Dislocation glide at a (100) SixGe1−x/Si interface

Krishna Rajan

Appl. Phys. Lett. 59, 2564 (1991); http://dx.doi.org/10.1063/1.105955 (3 pages) | Cited 5 times

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An unusual fourfold extended dislocation node at a SixGe1−x/Si strained layer interface has been revealed using weak‐beam electron microscopy. A detailed contrast analysis shows that this node structure is the result of the constriction of Lomer–Cottrell dislocations formed by intersecting slip dislocations on {100} and {111} type planes. This mechanism necessitates the glissile behavior of dislocation nodes at the (100) epitaxial interface.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Nn Stacking faults and other planar or extended defects

Microvolume‐secondary ion mass spectrometry analysis of nonvolatile sulfur residues in semiconductor process solutions

V. K. F. Chia, R. J. Bleiler, D. B. Sams, A. Y. Craig, and R. W. Odom

Appl. Phys. Lett. 59, 2567 (1991); http://dx.doi.org/10.1063/1.105956 (3 pages) | Cited 1 time

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The capability to detect and quantify sulfur at the part‐per‐billion (ppb) concentration level in ultrapure hydrochloric acid rinse solutions used in GaAs wafer fabrication is described. Nonvolatile residues formed from the deposition of nanoliter aliquots of solution onto high purity silicon wafers are analyzed using a high performance CAMECA IMS 4f ion microanalyzer. The dynamic SIMS analysis of microdroplet residues is referred to as Microvolume‐SIMS (MV‐SIMS). The Microvolume‐SIMS analyses of two acid solutions are presented. The concentration of total sulfur detected in these solutions was 98 and 650 ppb; both values are below the SEMI specification standard of less than 1300 ppb total sulfur concentration. Despite this, the acid solution containing 650 ppb of total sulfur was responsible for causing an isolation failure halting wafer production. This finding corroborated electrical failure analyses using these same acids.
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85.40.Hp Lithography, masks and pattern transfer
81.65.-b Surface treatments
07.75.+h Mass spectrometers

Room‐temperature annealing of Si implantation damage in InP

U. G. Akano, I. V. Mitchell, and F. R. Shepherd

Appl. Phys. Lett. 59, 2570 (1991); http://dx.doi.org/10.1063/1.105957 (3 pages) | Cited 9 times

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Spontaneous recovery at 295 K of Si implant damage in InP is reported. InP(Zn) and InP(S) wafers of (100) orientation have been implanted at room temperature with 600 keV Si+ ions to doses ranging from 3.6×1011 to 2×1014 cm−2. Room‐temperature annealing of the resultant damage has been monitored by the Rutherford backscattering/channeling technique. For Si doses ≤4×1013 cm−2, up to 70% of the initial damage (displaced atoms) annealed out over a period of ≊85 days. The degree of recovery was found to depend on the initial level of damage. Recovery is characterized by at least two time constants t1<5 days and a longer t2≊100 days. Anneal rates observed between 295 and 375 K are consistent with an activation energy of 1.2 eV, suggesting that the migration of implant‐induced vacancies is associated with the reordering of the InP lattice.
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61.72.U- Doping and impurity implantation
61.72.jd Vacancies
61.72.jj Interstitials
61.80.Jh Ion radiation effects
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Vertically coupled InGaAsP/InP buried rib waveguide filter

R. C. Alferness, L. L. Buhl, U. Koren, B. I. Miller, M. Young, and T. L. Koch

Appl. Phys. Lett. 59, 2573 (1991); http://dx.doi.org/10.1063/1.105958 (3 pages) | Cited 5 times

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We report the first demonstration of narrowband (<17 Å full width at half maximum) wavelength selective grating‐assisted coupling between vertically stacked buried rib InGaAsP/InP channel waveguides. These vertically coupled channel waveguides form the basis both of integrable filters essential to photonic circuits such as amplifier/filter and demultiplexer/detector circuits as well as a general approach to vertical integration of photonic circuits.
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42.79.Gn Optical waveguides and couplers
42.79.Ci Filters, zone plates, and polarizers
42.82.-m Integrated optics
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Removing native oxide from Si(001) surfaces using photoexcited fluorine gas

Takayuki Aoyama, Tatsuya Yamazaki, and Takashi Ito

Appl. Phys. Lett. 59, 2576 (1991); http://dx.doi.org/10.1063/1.105930 (3 pages) | Cited 3 times

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This letter discusses the reaction between (001) oriented Si surfaces and photoexcited fluorine gas resulting in the removal of the native Si oxide. For an F2/Ar gas system, the bulk Si was etched in areas where the native Si oxide had been completely removed. However, by using an F2/H2 gas system, only the native Si oxide was removed. We used this method to remove the native Si oxide in Si epitaxial growth. A high‐quality single‐crystal Si film surface was obtained up to a maximum temperature of 600 °C through this Si growth process. We also characterized the etching of a thermal oxide, silicon nitride, and silicon carbide.
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81.65.-b Surface treatments
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

New deep level luminescence bands observed from both a SiGe alloy layer and Si/Ge superlattice structures

V. Higgs, E. C. Lightowlers, G. F. A. van de Walle, D. J. Gravesteijn, and E. A. Montie

Appl. Phys. Lett. 59, 2579 (1991); http://dx.doi.org/10.1063/1.105908 (3 pages)

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Photoluminescence measurements have been made on Si/Ge short period superlattice structures grown on a SiGe alloy buffer layer and on a similar SiGe alloy layer without a superlattice. Using an InSb detector with a low energy cutoff at ∼450 meV, the major luminescence features observed were two broad bands with maximum intensities at ∼530 and ∼720 meV. The luminescence intensity was found to vary with the superlattice composition but was substantially stronger for the SiGe alloy layer without a superlattice. We ascribe these luminescence features to defects in the SiGe alloy layers. This is supported by the observation that the introduction of deliberate copper contamination at 600 °C dramatically increases the photoluminescence signal.
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78.55.Hx Other solid inorganic materials
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.66.Sq Composite materials
61.72.-y Defects and impurities in crystals; microstructure

AlGaAs/GaAs heterojunction bipolar transistor with a two‐dimensional electron gas emitter

Q. Wang, Y. Wang, K. F. Longenbach, E. S. Yang, and W. I. Wang

Appl. Phys. Lett. 59, 2582 (1991); http://dx.doi.org/10.1063/1.105909 (3 pages) | Cited 3 times

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We report the operation of the first two‐dimensional electron gas (2‐DEG) emitter heterojunction bipolar transistor. This device, which was grown by molecular beam epitaxy, incorporates an undoped GaAs spacer between the emitter and base of a standard AlGaAs/GaAs single‐heterojunction bipolar transistor. The introduction of the spacer layer causes the formation of a 2‐DEG at the AlGaAs/GaAs interface. This 2‐DEG defines the emitter side of the junction and produces an emitter‐base characteristic similar to that of the collector GaAs homojunction. Using a 300 Å GaAs spacer, offset voltages as low as 30 mV have been attained. These devices also exhibit current gains greater than 10 at emitter current densities of 3 A/cm2 and gains up to 400 in the high current density regime.
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85.30.Pq Bipolar transistors
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

First direct observation of voids in bulk, undoped, semi‐insulating GaAs

G. M. Williams, A. G. Cullis, and D. J. Stirland

Appl. Phys. Lett. 59, 2585 (1991); http://dx.doi.org/10.1063/1.105910 (3 pages) | Cited 12 times

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Defect selective A/B chemical etching, low‐temperature scanning cathodoluminescence, and transmission electron microscopy have been used to study the microstructure of undoped, semi‐insulating liquid‐encapsulated Czochralski GaAs wafers. It is shown for the first time that a distribution of microvoids is present in the bulk material at a number density of at least 1010 cm−3. These microvoids, which are present in the centers of the dislocation cell structures observed in the GaAs, may result from the post‐growth heat treatment of ingots which is used to improve the material homogeneity. A possible explanation for the formation of these microvoids is given. 
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61.72.J- Point defects and defect clusters
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.40.Gh Other heat and thermomechanical treatments

Si1−xGex/Si multiple quantum well infrared detector

R. P. G. Karunasiri, J. S. Park, and K. L. Wang

Appl. Phys. Lett. 59, 2588 (1991); http://dx.doi.org/10.1063/1.105911 (3 pages) | Cited 56 times

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A long‐wavelength infrared detector is demonstrated using Si1−xGex/Si multiple quantum wells for the first time. A broad peak in the photoresponse is observed near 9 μm with a full width at half maximum of about 80 meV which provides the response in the 6–12 μm range. The position of the peak in the photoresponse is in good agreement with that observed in the absorption measurement using a waveguide geometry. A peak responsivity of about 0.3 A/W and detectivity of D∗=1×109 cm √Hz/W at 77 K are achieved. This suggests the possibility of monolithic integration of Si1−xGex/Si multiple quantum well detectors with signal processing electronics for potential focal plane array applications.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
73.50.Pz Photoconduction and photovoltaic effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Anomalous Hall effect and the anomalous infrared absorption in n‐type bulk Hg0.8Cd0.2Te

J. G. Tian, C. P. Zhang, and G. Y. Zhang

Appl. Phys. Lett. 59, 2591 (1991); http://dx.doi.org/10.1063/1.105912 (3 pages) | Cited 7 times

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The anomalous Hall effects and the anomalous infrared absorption dependence on temperature have been observed in n‐type bulk Hg0.8Cd0.2Te in the temperature range between 5 and 300 K. The existence of p‐type inclusions in an n‐type matrix is considered as the cause of the anomalies. IR spectrum measurement is suggested to be employed to investigate the anomalous effects in bulk HgCdTe crystal.  
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72.15.Jf Thermoelectric and thermomagnetic effects
78.30.Fs III-V and II-VI semiconductors
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys

Patterning of epitaxial YBa2Cu3Ox insulator multilayers with a high‐temperature‐resistant lift‐off mask

B. Roas

Appl. Phys. Lett. 59, 2594 (1991); http://dx.doi.org/10.1063/1.105913 (3 pages) | Cited 5 times

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A new process for patterning of YBa2Cu3Ox‐insulator multilayers is described, using a high‐temperature‐resistant CaO process mask, which can be evaporated directly onto previously patterned YBa2Cu3Ox layers and removed after film deposition. A crossover contact of two 3 μm wide and 30 μm long YBa2Cu3Ox striplines has been fabricated by laser deposition, using this patterning technique. The upper and the lower stripline of the crossover contact show Tc values of ≊89 K and a critical current density jc (77 K) of 2 and 4×106 A/cm2, respectively. The contact between the upper and the lower stripline is superconducting below 87 K. At 100 K, the normal conducting contact resistivity is 5×10−8 Ω cm2, based on a contact area of 3×3 μm.
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74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures
85.40.Hp Lithography, masks and pattern transfer
85.40.Ls Metallization, contacts, interconnects; device isolation

Growth of (Pb0.75Cu0.25)Sr2(Y1−yCay)Cu2O7 thin films by laser ablation

R. A Hughes, Y. Lu, T. Timusk, and J. S. Prestón

Appl. Phys. Lett. 59, 2597 (1991); http://dx.doi.org/10.1063/1.105914 (3 pages) | Cited 2 times

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In this letter we investigate the effects of varying the values of x and y in (Pb1−xCux)Sr2(Y1−yCay)Cu2O7 films deposited by laser ablation. The films are grown in situ on (100) LaAlO3 at the relatively low substrate temperature of 620 °C. The films are highly oriented with the c‐axis perpendicular to the substrate and exhibit a surface morphology which is unique to the oxide superconductors. By substituting Ca for Y it is possible to systematically vary the superconducting transition temperature from 10 K to a maximum of 86 K. On the other hand, variations in the value of x seem to suggest that the film’s copper concentration in the (PbCu) plane can only exist within the narrow range of approximately x=0.2–0.3 and any extra copper added to the target ends up in an impurity phase.
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74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures

Critical‐current enhancement in particle‐irradiated cuprate semiconductors

B. D. Weaver, M. E. Reeves, G. P. Summers, R. J. Soulen, W. L. Olson, M. M. Eddy, T. W. James, and E. J. Smith

Appl. Phys. Lett. 59, 2600 (1991); http://dx.doi.org/10.1063/1.105915 (3 pages) | Cited 9 times

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Detailed measurements have been made of the magnetic field (0<H<6 T) and temperature (10 K<T<100 K) dependencies of the critical current density jc in Tl2CaBa2Cu2O8 films before and after irradiation with incremental fluences (0<Φ<3×1016 cm−2) of 2 MeV protons. The results are interpreted quantitatively in terms of radiation‐induced changes in (1) the critical temperature, (2) the rate of thermal flux creep, and (3) local scale superconductivity. Radiation‐induced enhancements in jc are described by an expression which allows the fluence that maximizes jc to be predicted as a function of H, T, pinning energy, and particle type.
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74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.70.-b Superconducting materials other than cuprates

High‐temperature dc superconducting quantum interference device with deep‐submicron YBa2Cu3O7 weak links

Suzanne E. Romaine, Paul M. Mankiewich, William J. Skocpol, and Eric Westerwick

Appl. Phys. Lett. 59, 2603 (1991); http://dx.doi.org/10.1063/1.105916 (3 pages) | Cited 4 times

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We have fabricated a YBa2Cu3O7 (YBCO) thin‐film dc superconducting quantum interference device (SQUID) with lithographically defined deep‐submicron weak links. At 77 K the voltage response to dc flux is sinusoidal and nonhysteretic, with maximum peak‐to‐peak amplitude of 5 μV. The maximum response is 8 μV at 70 K, where 2LI0/Φ0≊1. At lower temperatures, the maximum response oscillates in the range 4–6 μV. Random telegraph noise was observed near 30–40 K. Well‐behaved Shapiro steps were observable at all measured temperatures below Tc.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.70.-b Superconducting materials other than cuprates

Epitaxial growth and properties of YBa2Cu3O7−δ/NdGaO3/YBa2Cu3O7−δ trilayer structures

Yu. Boikov, G. Brorsson, T. Claeson, and Z. G. Ivanov

Appl. Phys. Lett. 59, 2606 (1991); http://dx.doi.org/10.1063/1.105917 (3 pages) | Cited 17 times

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We have used laser deposition to make YBa2Cu3O7−δ/NdGaO3/YBa2Cu3O7−δ trilayer structures. NdGaO3 films grow epitaxially on well lattice‐matched substrates, like SrTiO3 (100), and on c‐axis oriented YBa2Cu3O7−δ films. Epitaxial YBa2Cu3O7−δ films were grown on top of the NdGaO3 films, and there was no significant difference in critical temperature between top and bottom layers of the trilayer structures. The resistivity of a 300‐nm‐thick NdGaO3 interlayer was as high as 108 Ω cm at 300 K.
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85.25.-j Superconducting devices
74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures
74.78.Fk Multilayers, superlattices, heterostructures

Sub‐μm, planarized, Nb‐AlOx‐Nb Josephson process for 125 mm wafers developed in partnership with Si technology

M. B. Ketchen, D. Pearson, A. W. Kleinsasser, C.‐K. Hu, M. Smyth, J. Logan, K. Stawiasz, E. Baran, M. Jaso, T. Ross, K. Petrillo, M. Manny, S. Basavaiah, S. Brodsky, S. B. Kaplan, et al.

Appl. Phys. Lett. 59, 2609 (1991); http://dx.doi.org/10.1063/1.106405 (3 pages) | Cited 47 times

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We have demonstrated a new planarized all‐refractory technology for low Tc superconductivity (PARTS). With the exception of the Nb‐AlOx‐Nb trilayer preparation, the processing is done almost exclusively within an advanced Si technology fabrication facility. This approach has allowed us to leverage highly off of existing state‐of‐the‐art lithography, metal etching, materials deposition, and planarization capabilities. Using chemical‐mechanical polish as the planarization technique we have fabricated Josephson junctions ranging in size from 0.5–100 μm2. Junction quality is excellent with the figure of merit Vm typically exceeding 70 mV. PARTS has yielded fully functional integrated Josephson devices including magnetometers, gradiometers, and soliton oscillators.
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85.40.Hp Lithography, masks and pattern transfer
85.25.Cp Josephson devices
85.25.Dq Superconducting quantum interference devices (SQUIDs)

Reduced flux motion via flux creep annealing in high‐ Jc single‐crystal Y1Ba2Cu3O7

J. R. Thompson, Yang Ren Sun, A. P. Malozemoff, D. K. Christen, H. R. Kerchner, J. G. Ossandon, A. D. Marwick, and F. Holtzberg

Appl. Phys. Lett. 59, 2612 (1991); http://dx.doi.org/10.1063/1.105918 (3 pages) | Cited 17 times

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We investigated the stabilization of magnetic flux in a high‐temperature superconductor (a proton‐irradiated Y1Ba2Cu3O7 crystal), by operating with subcritical current density J. Using the thermal history to obtain an induced current density J≤Jc, we observed a drastically reduced relaxation rate dM/dt (M=magnetization), after ‘‘flux creep annealing.’’ The results show that the field gradient ∼J∼M determined the relaxation rate, independent of the sample’s H‐T history, in agreement with recent theory.
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74.25.-q Properties of superconductors
74.70.-b Superconducting materials other than cuprates

Effect of cable and strand twist‐pitch coincidence on the critical current of flat, coreless superconductor cablesa)

J. W. Ekin

Appl. Phys. Lett. 59, 2615 (1991); http://dx.doi.org/10.1063/1.105919 (3 pages) | Cited 3 times

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Data are presented which indicate that a very simple technique for enhancing the critical current in flat, coreless superconductor cables is to match the cable twist pitch with the strand twist pitch in such a way that the same group of filaments within each strand is degraded at each successive bend at the cable edges. This coincidence condition minimizes current transfer among filaments, enhances the slope of the voltage‐current characteristic, consistently improves the critical current by about 10% in these tests, and is easy to apply.
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84.71.Ba Superconducting magnets; magnetic levitation devices
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.25.-q Properties of superconductors
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