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1 Jul 2002

Volume 81, Issue 1, pp. 1-184

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Comparative study of InGaAs quantum dot lasers with different degrees of dot layer confinement

K. M. Groom, A. I. Tartakovskii, D. J. Mowbray, M. S. Skolnick, P. M. Smowton, M. Hopkinson, and G. Hill

Appl. Phys. Lett. 81, 1 (2002); http://dx.doi.org/10.1063/1.1489702 (3 pages) | Cited 27 times

Online Publication Date: 25 June 2002

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We report a comparative study of the gain and lasing characteristics of two different InGaAs quantum dot (QD) laser designs, with multiple QD layers separated by barriers of (A) GaAs or (B) GaAs/AlGaAs. A higher degree of carrier confinement in structure B results in superior lasing characteristics at elevated temperatures. However, at temperatures below 130 K these devices demonstrate inhomogeneously broadened gain spectra, resulting in lasing over a much wider energy range than for structure A. The results are consistent with inefficient, low temperature interdot carrier transport in devices based on structure B. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Oxadiazole-containing material with intense blue phosphorescence emission for organic light-emitting diodes

Fushun Liang, Lixiang Wang, Dongge Ma, Xiabin Jing, and Fosong Wang

Appl. Phys. Lett. 81, 4 (2002); http://dx.doi.org/10.1063/1.1491288 (3 pages) | Cited 25 times

Online Publication Date: 25 June 2002

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2-(2-hydroxyphenyl)-5-phenyl-1, 3, 4-oxadiazole (HOXD), characteristic of excited state intramolecular proton-transfer (ESIPT), was synthesized and found to emit strong blue phosphorescence in the solid state at room temperature and at low temperature (77 K). The photoluminescent spectrum measurement in solution showed that there are two kinds of emission: fluorescence originated from the singlet state and phosphorescence derived from the triplet state in HOXD formed by ESIPT. For the photoluminescent spectrum in the solid state, only phosphorescence emission with the lifetime of 66 μs was observed. Multiple-layer light-emitting diodes with the configuration of ITO/NPB/HOXD/BCP/Alq3/Mg:Ag were fabricated using HOXD as emitter and the maximum brightness of 656 cd/m2 and the luminous efficiency of 0.14 lm/W was obtained. © 2002 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.55.Bq Liquids

Three-dimensional imaging of a silicon flip chip using the two-photon optical-beam induced current effect

E. Ramsay, D. T. Reid, and K. Wilsher

Appl. Phys. Lett. 81, 7 (2002); http://dx.doi.org/10.1063/1.1491301 (3 pages) | Cited 18 times

Online Publication Date: 25 June 2002

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We describe two- and three-dimensional imaging of a flip-chip silicon integrated circuit using backside optical probing and femtosecond two-photon excitation at a laser wavelength of 1.275 μm. Using a ×50 microscope objective, we typically achieved micron resolutions or better in both lateral and axial directions. Using axial scanning and a peak-detection algorithm we have demonstrated optical depth profiling across components on the chip. © 2002 American Institute of Physics.
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07.60.Pb Conventional optical microscopes
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
06.60.Jn High-speed techniques (microsecond to femtosecond)
78.47.-p Spectroscopy of solid state dynamics
72.40.+w Photoconduction and photovoltaic effects
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
07.79.Fc Near-field scanning optical microscopes

Organic-film photovoltaic cell with electroluminescence

B. Chu, D. Fan, W. L. Li, Z. R. Hong, and R. G. Li

Appl. Phys. Lett. 81, 10 (2002); http://dx.doi.org/10.1063/1.1488699 (3 pages) | Cited 21 times

Online Publication Date: 25 June 2002

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An organic-film photovoltaic (PV) cell, in which N,N′-bis-(1-naphthyl)- N,N′- diphenyl- 1,1′- biphenyl-4,4′-diamine (NPB) and tris(acetylacetonato)-(monophenothroline) yttrium [Y(ACA)3phen] were used as electron-acceptor and donor, respectively, has been fabricated. Under UV light (4 mW/cm2), the short-circuit current (Isc), open-circuit voltage (Voc), fill factor (FF) and the overall power conversion efficiency of the optimum PV cell were 46 μA/cm2, 2.15 V, 0.30%, and 0.7%, respectively. The photocurrent response region of the cell parallels the adsorption of NPB. The PV effect is attributed to exciplex formation at the interface between the two organic films. The PV cell described displays electroluminescence (EL) emission of blue light upon application of a dc voltage. The maximum luminance was 750 cd/m2 at 15 V driving voltage. © 2002 American Institute of Physics.
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85.60.-q Optoelectronic devices
72.40.+w Photoconduction and photovoltaic effects
73.50.Pz Photoconduction and photovoltaic effects
78.60.Fi Electroluminescence

Tunable terahertz generation using femtosecond pulse shaping

J. Y. Sohn, Y. H. Ahn, D. J. Park, E. Oh, and D. S. Kim

Appl. Phys. Lett. 81, 13 (2002); http://dx.doi.org/10.1063/1.1490140 (3 pages) | Cited 22 times

Online Publication Date: 25 June 2002

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Femtosecond pulse shaping and photomixing methods are combined to make a tunable terahertz source. Grating-pair pulse shaper selects two main frequency components to produce pulses that are modulated with a period which is inversely proportional to the frequency separation. The shaped pulse is then photomixed in semi-insulating GaAs under external bias. Terahertz (THz) emission frequency follows the modulation frequency of the excitation pulses, from 0.5 to 3 THz. Contrary to cw photomixing, this method can easily be combined with electro-optic and photoconductive sampling detection methods. © 2002 American Institute of Physics.
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07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
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N2–H2 remote plasma nitridation for GaAs surface passivation

Maria Losurdo, P. Capezzuto, G. Bruno, G. Perna, and V. Capozzi

Appl. Phys. Lett. 81, 16 (2002); http://dx.doi.org/10.1063/1.1490414 (3 pages) | Cited 8 times

Online Publication Date: 25 June 2002

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A remote N2–H2 (a mixture of 97% N2–3% H2) rf plasma nitridation procedure has been developed to form a very thin ( ∼ 5Å) GaN layer successful in the electronic and chemical passivation of GaAs (100) surfaces. The interaction of the plasma with the GaAs surface has been controlled in situ and in real time by spectroscopic ellipsometry. The stability of the chemical and electronic passivation is demonstrated by the nonoxidation and by the nondecaying behavior of the photoluminescence efficiency of the GaAs passivated surface over months of air exposure. © 2002 American Institute of Physics.
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81.65.Rv Passivation
81.05.Ea III-V semiconductors
81.65.Lp Surface hardening: nitridation, carburization, carbonitridation
52.77.-j Plasma applications
78.55.Cr III-V semiconductors
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Atomic oxygen surface loss coefficient measurements in a capacitive/inductive radio-frequency plasma

S. Gomez, P. G. Steen, and W. G. Graham

Appl. Phys. Lett. 81, 19 (2002); http://dx.doi.org/10.1063/1.1490630 (3 pages) | Cited 49 times

Online Publication Date: 25 June 2002

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Spatially resolved measurements of the atomic oxygen densities close to a sample surface in a dual mode (capacitive/inductive) rf plasma are used to measure the atomic oxygen surface loss coefficient β on stainless steel and aluminum substrates, silicon and silicon dioxide wafers, and on polypropylene samples. β is found to be particularly sensitive to the gas pressure for both operating modes. It is concluded that this is due to the effect of changing atom and ion flux to the surface. © 2002 American Institute of Physics.
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52.80.Pi High-frequency and RF discharges
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.25.-b Plasma properties
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Selective-area growth of indium nitride nanowires on gold-patterned Si(100) substrates

C. H. Liang, L. C. Chen, J. S. Hwang, K. H. Chen, Y. T. Hung, and Y. F. Chen

Appl. Phys. Lett. 81, 22 (2002); http://dx.doi.org/10.1063/1.1490636 (3 pages) | Cited 101 times

Online Publication Date: 25 June 2002

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This letter reports the synthesis of indium nitride (InN) nanowires on gold-patterned silicon substrates in a controlled manner using a method involving thermal evaporation of pure indium. The locations of these InN nanowires were controlled by depositing gold in desired areas on the substrates. Scanning electron microscopy and transmission electron microscopy investigations showed that the InN nanowires are single crystals with diameters ranging from 40 to 80 nm, and lengths up to 5 μm. Energy dispersive x-ray spectrometry showed that the ends of the nanowires are composed primarily of Au, and the rest of the nanowires were InN with no detectable Au incorporations. The Raman spectra showed peaks at 445, 489, and 579 cm−1, which are attributed to the A1(transverse optical), E2, and A1(longitudinal optical) phonon modes of the wurtzite InN structure, respectively. Photoluminescence spectra of the InN nanowires showed a strong broad emission peak at 1.85 eV. © 2002 American Institute of Physics.
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68.65.La Quantum wires (patterned in quantum wells)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
78.67.Lt Quantum wires
78.55.Cr III-V semiconductors
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
68.35.Ja Surface and interface dynamics and vibrations
78.30.Fs III-V and II-VI semiconductors

Direct determination of grain sizes, lattice parameters, and mismatch of porous silicon

R. J. Martín-Palma, L. Pascual, P. Herrero, and J. M. Martínez-Duart

Appl. Phys. Lett. 81, 25 (2002); http://dx.doi.org/10.1063/1.1491007 (3 pages) | Cited 32 times

Online Publication Date: 25 June 2002

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High-resolution transmission electron microscopy and digital image processing were used to investigate in detail the structure of porous silicon (PS). It was found that PS is composed of rounded Si nanocrystals with characteristic sizes between 21 and 80 Å, embedded into an amorphous matrix and with no preferential orientation. We have determined that the size distribution of the nanocrystals can be fitted to a Gaussian distribution centered at 45.89 Å. Furthermore, the structure of the individual Si grains was studied, which allowed us to determine that the interplanar distance varies from 3.17 to 3.41 Å, with Gaussian distribution centered at 3.24 Å. Finally, the lattice parameter of the individual Si grains that compose PS was also measured, showing a Gaussian distribution centered at 5.61 Å. The origin of the structure of PS is also discussed. © 2002 American Institute of Physics.
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61.46.-w Structure of nanoscale materials

Sol-gel Er-doped SiO2–HfO2 planar waveguides: A viable system for 1.5 μm application

R. R. Gonçalves, G. Carturan, L. Zampedri, M. Ferrari, M. Montagna, A. Chiasera, G. C. Righini, S. Pelli, S. J. L. Ribeiro, and Y. Messaddeq

Appl. Phys. Lett. 81, 28 (2002); http://dx.doi.org/10.1063/1.1489477 (3 pages) | Cited 18 times

Online Publication Date: 25 June 2002

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70SiO2–30HfO2 planar waveguides, doped with Er3+ concentrations ranging from 0.3 to 1 mol %, were prepared by sol-gel route, using dip-coating deposition on silica glass substrates. The waveguides show high densification degree, effective intermingling of the two components of the film, and uniform surface morphology. Propagation losses of about 1 dB/cm were measured at 632.8 nm. When pumped with 987 or 514.5 nm continuous-wave laser light, the waveguides show the 4I13/2→4I15/2 emission band with a bandwidth of 48 nm. The spectral features are found independent both on erbium content and excitation wavelength. The 4I13/2 level decay curves presented a single-exponential profile, with a lifetime between 2.9 and 5.0 ms, depending on the erbium concentration. © 2002 American Institute of Physics.
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42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.35.B- Structure of clean surfaces (and surface reconstruction)

Thermal conductance and electron-phonon coupling in mechanically suspended nanostructures

C. S. Yung, D. R. Schmidt, and A. N. Cleland

Appl. Phys. Lett. 81, 31 (2002); http://dx.doi.org/10.1063/1.1491300 (3 pages) | Cited 26 times

Online Publication Date: 25 June 2002

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We have fabricated and characterized the principal thermal properties of a mechanically suspended nanostructure, consisting of a micron-scale suspended GaAs island, upon which we have defined superconductor-insulator-normal metal tunnel junctions. The tunnel junctions allow for sensitive thermometry and heating of the electrons in a thermally isolated normal metal element, permitting the determination of the low-temperature thermal conductance of the legs that support the GaAs island, as well as the low-temperature electron-phonon coupling. This device forms the basis of a nanoscale bolometric detector, whose optical performance can be estimated from these measurements. © 2002 American Institute of Physics.
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07.20.Dt Thermometers
73.63.Rt Nanoscale contacts
61.46.-w Structure of nanoscale materials
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves

Green emission from B2N2CO thin films doped with Tb

Q. L. Liu, F. X. Zhang, T. Tanaka, and T. Aizawa

Appl. Phys. Lett. 81, 34 (2002); http://dx.doi.org/10.1063/1.1490143 (3 pages) | Cited 9 times

Online Publication Date: 25 June 2002

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Visible light emission has been obtained at room temperature by photoluminescence (PL) and cathodoluminescence (CL) from Tb-doped B2N2CO thin films prepared by radio-frequency magnetron sputtering. The films were deposited by sputtering TbBn (n = 4, 6, 12, 25, and 50) targets in an atmosphere of Ar and N2 gas mixture. The films are uniformly composed of very small particles with particle size of about 20–40 nm, which consist of turbostratic BN phase and amorphous phase. The characteristic PL peaks are observed in the spectral range from 300 to 800 nm, and correspond to the two groups of transitions of Tb3+ ions: 5D3→7FJ (J = 6, 5, 3) and 5D4→7FJ (J = 6, 5, 4, 3). The strongest PL peak at ∼ 547.2 nm is about four times greater than the other signals in the investigated range, indicating that the films have strong green light emission. CL intensity is very weakly dependent on the temperature. © 2002 American Institute of Physics.
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78.66.Li Other semiconductors
78.55.Hx Other solid inorganic materials
78.60.Hk Cathodoluminescence, ionoluminescence
68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering

Formation of epitaxial CoSi2 films on Si and on Si/Si80Ge20 (100) by reactive deposition epitaxy

G. Pető, G. Molnár, E. Kótai, I. Dézsi, M. Karsteen, U. Södervall, M Willander, M. Caymax, and R. Loo

Appl. Phys. Lett. 81, 37 (2002); http://dx.doi.org/10.1063/1.1491012 (3 pages) | Cited 3 times

Online Publication Date: 25 June 2002

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CoxTi1−x layers were deposited on Si (100) and on Si/Si80Ge20 (100) capped with 30- or 40-nm-thick Si at 650 °C substrate temperature at 1×10−6 Pa pressure. The Co–silicide films grown by reactive deposition epitaxy were characterized by Rutherford backscattering-channeling, x-ray difraction, by depth profile analysis of the components, and by sheet resistance measurements. The Ti content of the deposited Co layers was between 0.1 and 8 at. %. The epitaxy of the layers on Si and on Si/Si80Ge20 improved by increasing the Ti concentration. The minimum yield of the channeling and the full width at half maximum value of the rocking curve of CoSi2 decreased. The sheet resisitance of the formed layers was also minimal in these cases. The method applied is promising to form epitaxial CoSi2 layers on SixGe1−x substrates. © 2002 American Institute of Physics.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
73.61.At Metal and metallic alloys
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)

Platinum–hydrogen complexes in silicon observed by measurements of optical absorption and electron spin resonance

N. Fukata, T. Mchedlidze, M. Suezawa, K. Saito, and A. Kasuya

Appl. Phys. Lett. 81, 40 (2002); http://dx.doi.org/10.1063/1.1491008 (3 pages) | Cited 5 times

Online Publication Date: 25 June 2002

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Platinum–hydrogen (Pt–H) complexes in Si doped with Pt and H by heating at 1000–1300 °C followed by quenching in water were investigated from the measurements of optical absorption at 5 K and electron spin resonance (ESR) at 8 K. Optical absorption peaks at 1909.1 and 1910.3 cm−1 were observed in addition to the peaks due to the PtH and PtH2 complexes. The H doping temperature dependence of these peaks showed that the number of H atoms in the complex responsible for the 1909.1 cm−1 peak is larger than that for the 1910.3 cm−1 peak. We also observed ESR signals due to the PtH3 complex. The annealing behaviors of the 1910.3 cm−1 peak and the ESR signals were almost the same. Based on these results, the 1909.1 and 1910.3 cm−1 peaks are, respectively, assigned to the PtH4 complex and the PtH3 complex. © 2002 American Institute of Physics.
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78.40.Fy Semiconductors
76.30.He Platinum and palladium group (4d and 5d) ions and impurities (Zr-Ag and Hf-Au)
61.72.S- Impurities in crystals
61.72.Cc Kinetics of defect formation and annealing
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Grain structure effects on the lattice thermal conductivity of Ti-based half-Heusler alloys

S. Bhattacharya, Terry M. Tritt, Y. Xia, V. Ponnambalam, S. J. Poon, and N. Thadhani

Appl. Phys. Lett. 81, 43 (2002); http://dx.doi.org/10.1063/1.1488698 (3 pages) | Cited 31 times

Online Publication Date: 25 June 2002

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Half-Heusler alloys with the general formula TiNiSn1−xSbx are currently being investigated for their potential as thermoelectric (TE) materials. A systematic investigation of the effect of Sb doping on the Sn site and Zr doping on the Ti site on the electrical and thermal transport of the TiNiSn system has been performed. Unexpectedly, lattice thermal conductivity κL appears to increase somewhat randomly with small amounts (x<5%) of Sb doping. Subsequently, an investigation of grain structure in these Sb-doped materials has been found to correlate with the anomalous behavior of κL. Furthermore, effects of submicron grain sizes on κL in ball milled and shock compressed samples are also presented. © 2002 American Institute of Physics.
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72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
72.15.Jf Thermoelectric and thermomagnetic effects
61.72.-y Defects and impurities in crystals; microstructure

Electronic and field emission properties of boron nitride/carbon nanotube superlattices

Vincent Meunier, Christopher Roland, J. Bernholc, and Marco Buongiorno Nardelli

Appl. Phys. Lett. 81, 46 (2002); http://dx.doi.org/10.1063/1.1491013 (3 pages) | Cited 27 times

Online Publication Date: 25 June 2002

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BN/C nanotube superlattices are quasi one-dimensional heterostructures that show unique physical properties derived from their peculiar geometry. Using state-of-the-art ab initio calculations, we show that BN/C systems can be used for effective band-offset nanodevice engineering, polarization-based devices, and robust field emitters with an efficiency enhanced by up to two orders of magnitude over carbon nanotube systems. © 2002 American Institute of Physics.
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73.21.Cd Superlattices
73.22.Dj Single particle states
79.70.+q Field emission, ionization, evaporation, and desorption
73.63.Fg Nanotubes
61.46.-w Structure of nanoscale materials
71.15.-m Methods of electronic structure calculations

Quantum wells with atomically smooth interfaces

Masahiro Yoshita, Hidefumi Akiyama, Loren N. Pfeiffer, and Ken W. West

Appl. Phys. Lett. 81, 49 (2002); http://dx.doi.org/10.1063/1.1490144 (3 pages) | Cited 30 times

Online Publication Date: 25 June 2002

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By a cleaved-edge overgrowth method with molecular beam epitaxy and a (110) growth-interrupt anneal, we have fabricated a GaAs quantum well exactly 30 monolayers thick bounded by atomically smooth AlGaAs heterointerfaces without atomic roughness. Microphotoluminescence imaging of this quantum well indeed shows spatially uniform and spectrally sharp emission over areas of several tens of microns in extent. By adding a fractional GaAs monolayer to our quantum well we are able to study the details of the atomic step-edge kinetics responsible for flat interface formation. © 2002 American Institute of Physics.
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68.65.Fg Quantum wells
78.67.De Quantum wells
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
81.07.St Quantum wells
68.35.Ct Interface structure and roughness
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Time-resolved studies of photoluminescence in GaNxP1−x alloys: Evidence for indirect-direct band gap crossover

I. A. Buyanova, G. Pozina, J. P. Bergman, W. M. Chen, H. P. Xin, and C. W. Tu

Appl. Phys. Lett. 81, 52 (2002); http://dx.doi.org/10.1063/1.1491286 (3 pages) | Cited 32 times

Online Publication Date: 25 June 2002

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Time resolved photoluminescence spectroscopy is employed to monitor the effect of N incorporation on the band structure of GaNP alloys. Abrupt shortening in radiative lifetime of near-band gap emissions, arising from excitonic radiative recombination within N-related centers, is found to occur at very low N compositions of around 0.5%, i.e., within the same range as the appearance of the direct-band gap-like transitions in the photomodulated transmission spectra of GaNP reported previously. The effect has been attributed to an enhancement in oscillator strength of optical transitions due to band crossover from indirect to direct-band gap of the alloy. © 2002 American Institute of Physics.
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71.20.Nr Semiconductor compounds
78.55.Cr III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
71.35.-y Excitons and related phenomena
78.40.Fy Semiconductors

Effects of N-induced heterogeneous nucleation and growth of cavities at the CoSi2/polycrystalline–silicon interface

A. Alberti, F. La Via, and E. Rimini

Appl. Phys. Lett. 81, 55 (2002); http://dx.doi.org/10.1063/1.1488697 (3 pages) | Cited 3 times

Online Publication Date: 25 June 2002

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N-induced cavity nucleation at the CoSi2/Si interface has been investigated for different doses and its influence on improving the thermal stability of the silicide layer up to 1075 °C has been detailed. The N-implant energy and doses have been chosen in such a way that the projected range (Rp) was near the interface and the underlying polycrystalline silicon substrate was completely amorphized. After a thermal treatment of 975 °C, it has been found that the cavity density depends on the dose, but the cavity size is dose independent. The cavity density should be enough to saturate the silicide grain boundaries but not so high to neglect ripening and coalescence. A density of 2.5×1010 cavities/cm2 has been measured at a nitrogen dose of 7×1015/cm2 corresponding to a partial saturation of the silicide grain boundaries and to the higher stability gain (150 °C). © 2002 American Institute of Physics.
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61.72.Qq Microscopic defects (voids, inclusions, etc.)
61.82.Fk Semiconductors
61.80.Jh Ion radiation effects
61.72.Mm Grain and twin boundaries
61.72.uf Ge and Si
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
81.40.Gh Other heat and thermomechanical treatments
68.35.Ct Interface structure and roughness

Effect of doping on photoluminescence upconversion in GaAs/AlxGa1−xAs heterostructures

Hyeonsik M. Cheong, Doseok Kim, Mark C. Hanna, and Angelo Mascarenhas

Appl. Phys. Lett. 81, 58 (2002); http://dx.doi.org/10.1063/1.1491303 (3 pages) | Cited 1 time

Online Publication Date: 25 June 2002

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We report on the effect of doping on the efficiency of the upconverted photoluminescence (UPL) from GaAs/AlGaAs heterostructures. The UPL intensity is enhanced when the AlGaAs layer is remotely doped with holes. It indicates that the rate-limiting process for the upconversion is the excitation of holes. Our result shows that one has to be careful in interpreting the excitation power dependence of the UPL intensity because dissimilar excitation efficiencies for electrons and holes and a possible background doping of the samples can significantly modify the excitation power dependence. © 2002 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
61.72.uj III-V and II-VI semiconductors

Two-step As-desorption from (001) InP observed by surface photoabsorption

T. J. Kim, Y. S. Ihn, G. Y. Seong, Y. D. Kim, T. W. Lee, H. Hwang, S. Yoon, and E. Yoon

Appl. Phys. Lett. 81, 61 (2002); http://dx.doi.org/10.1063/1.1491299 (3 pages) | Cited 1 time

Online Publication Date: 25 June 2002

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The investigation of As desorption from the (001) InP during metalorganic chemical vapor deposition was performed using surface photoabsorption (SPA). The behavior of the monochromatic SPA signal showed a clear existence of a metastable state after the AsH3 was turned off. SPA spectra at each stable surface were taken to confirm the interpretation. This result indicates that the previous criterion to measure the amount of As/P exchange reaction is not necessarily correct and that the As-desorption process should be understood as a two-step process. © 2002 American Institute of Physics.
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68.43.Mn Adsorption kinetics
78.40.Fy Semiconductors
82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)
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Majority- and minority-carrier deep level traps in proton-irradiated n+/p-InGaP space solar cells

Nethaji Dharmarasu, Masafumi Yamaguchi, Jacques C. Bourgoin, Tatsuya Takamoto, Takeshi Ohshima, Hisayoshi Itoh, Mitsuru Imaizumi, and Sumio Matsuda

Appl. Phys. Lett. 81, 64 (2002); http://dx.doi.org/10.1063/1.1491005 (3 pages) | Cited 6 times

Online Publication Date: 25 June 2002

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We report the properties of observed defects in n+/p-InGaP solar cells created by irradiation of protons of different energies. Three majority (hole) and a minority-carrier traps, labeled respectively as HP1 (Ev+0.90±0.05 eV), HP2 (Ev+0.73±0.05 eV), H2 (Ev+0.55 eV), and EP1 (Ec−0.54 eV), were identified using deep level transient spectroscopy. All majority-carrier traps were found to act as recombination centers. While the H2 trap present in the proton-irradiated p-InGaP was found to anneal out by minority-carrier injection, the other traps were not. © 2002 American Institute of Physics.
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84.60.Jt Photoelectric conversion
71.55.Eq III-V semiconductors
61.82.Fk Semiconductors
61.80.Jh Ion radiation effects
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Terahertz intersubband emission in strong magnetic fields

Stéphane Blaser, Michel Rochat, Mattias Beck, Daniel Hofstetter, and Jérôme Faist

Appl. Phys. Lett. 81, 67 (2002); http://dx.doi.org/10.1063/1.1490629 (3 pages) | Cited 21 times

Online Publication Date: 25 June 2002

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Electroluminescence in quantum-cascade structures based on vertical transitions is studied in a strong perpendicular magnetic field in the limit in which the cyclotron energy is larger than the intersubband transition energy. Cyclotron emission and a luminescence intensity enhancement up to a factor of 6 is observed in GaAs/AlGaAs and InGaAs/InAlAs vertical transition-based quantum-cascade structures. © 2002 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.60.Fi Electroluminescence
78.20.Ls Magneto-optical effects

Low-resistivity, p-type SiC layers produced by Al implantation and ion-beam-induced crystallization

V. Heera, K. N. Madhusoodanan, A. Mücklich, D. Panknin, and W. Skorupa

Appl. Phys. Lett. 81, 70 (2002); http://dx.doi.org/10.1063/1.1490145 (3 pages) | Cited 7 times

Online Publication Date: 25 June 2002

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Low-resistivity (<0.1 Ω cm), p-type SiC layers of about 500 nm width and targeted acceptor concentrations of 1.5×1020 cm−3 and 5.0×1020 cm−3 were produced by the combination of high-dose (1.0 and 3.3×1016 cm−2), multienergy (50–450 keV) Al+ ion implantation of 6H-SiC at −130 °C, ion-beam-induced crystallization with 500 keV, 5×1015 Si+ cm−2 at 500 °C and subsequent furnace annealing at 1500 °C for 10 min. The implanted SiC layers have a nanocrystalline structure consisting of randomly oriented grains of mainly 3C-SiC. The electrical properties of the doped, nanocrystalline layers were investigated by sheet resistance and Hall measurements in dependence on temperature and compared with results from single-crystalline reference samples. In comparison with the standard doping process, the hole concentration at 50 °C is enhanced by more than one order of magnitude from 9.0×1017 cm−3 to 1.6×1019 cm−3 in the case of 1.5×1020 Al cm−3 and from 6.1×1018 cm−3 to 8.0×1019 cm−3 in the case of 5.0×1020 Al cm−3, respectively. It can be speculated that the loss of active Al acceptors by precipitation is reduced in the nanocrystalline layers and, therefore, the critical concentration for the formation of an impurity band can be achieved. © 2002 American Institute of Physics.
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61.72.up Other materials
61.80.Jh Ion radiation effects
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.61.Le Other inorganic semiconductors
61.82.Fk Semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.46.-w Structure of nanoscale materials
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
64.75.-g Phase equilibria
71.55.Ht Other nonmetals

n-type doping of oxides by hydrogen

Çetin Kılıç and Alex Zunger

Appl. Phys. Lett. 81, 73 (2002); http://dx.doi.org/10.1063/1.1482783 (3 pages) | Cited 90 times

Online Publication Date: 25 June 2002

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First-principles total-energy calculations suggest that interstitial hydrogen impurity forms a shallow donor in SnO2, CdO, and ZnO, but a deep donor in MgO. We generalize this result to other oxides by recognizing that there exist a “hydrogen pinning level” at about 3.0±0.4 eV below vacuum. Materials such as Ag2O, HgO, CuO, PbO, PtO, IrO2, RuO2, PbO2, TiO2, WO3, Bi2O3, Cr2O3, Fe2O3, Sb2O3, Nb2O5, Ta2O5, FeTiO3, and PbTiO3, whose conduction band minimum (CBM) lie below this level (i.e., electron affinity>3.0±0.4 eV) will become conductive once hydrogen is incorporated into the lattice, without reducing the host. Conversely, materials such as BaO, NiO, SrO, HfO2, and Al2O3, whose CBM lie above this level (i.e., electron affinity<3.0±0.4 eV) will remain nonconductive since hydrogen forms a deep impurity. © 2002 American Institute of Physics.
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71.55.Ht Other nonmetals
61.72.J- Point defects and defect clusters
71.15.Nc Total energy and cohesive energy calculations
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