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29 Apr 2002

Volume 80, Issue 17, pp. 3033-3231

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Boundary conditions in an electric current contact

O. Yu. Titov, J. Giraldo, and Yu. G. Gurevich

Appl. Phys. Lett. 80, 3108 (2002); http://dx.doi.org/10.1063/1.1473875 (3 pages) | Cited 14 times

Online Publication Date: 22 April 2002

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In most electronic devices, the electric current of both types (electrons and holes) flows through a junction. Usually the boundary conditions have been formulated exclusively for open circuit. The boundary conditions proposed here bypass this limitation. Besides, these boundary conditions correctly describe the current flow in a circuit, i.e., closed circuit conditions, which are the usual operation conditions for electronic devices and for the measurement of many transport properties. We also have generalized the case (as much as it is possible in a classical treatment), so self-consistent boundary conditions that describe the current flow through a contact between two arbitrary conducting media are developed in the present work. These boundary conditions take into account a recently developed theory: influence of temperature space inhomogeneity due to the interfaces and quasiparticles temperature mismatch on thermogeneration and recombination. They also take into account surface resistance, surface recombination rates, and possible temperature discontinuities at the interface due to finite surface thermoconductivity. The temperature difference between current carriers and phonon subsystems is also included in this approach. © 2002 American Institute of Physics.
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72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
73.40.Cg Contact resistance, contact potential

Band alignment between GaAs and partially ordered GaInP

Yong Zhang, Angelo Mascarenhas, and Lin-Wang Wang

Appl. Phys. Lett. 80, 3111 (2002); http://dx.doi.org/10.1063/1.1472478 (3 pages) | Cited 12 times

Online Publication Date: 22 April 2002

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An empirical pseudopotential method is used for calculating the band structure of partially CuPt ordered GaxIn1−xP alloy with order parameter η varying from 0 to 1. Because the relative band alignments between the binaries (GaAs, GaP, and InP) are taken into account in the pseudopotential fitting, such a calculation naturally yields the conduction and valence band alignment between the GaInP alloy and GaAs, as well as shows how the alignments change with the order parameter. The band alignment is found to change from type I to type II at η = 0.46 (0.54) for x = 0.50 (0.52), which is in good agreement with experimental data. © 2002 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)

Bias-dependent photoluminescence in CdTe photovoltaics

Diana Shvydka, V. G. Karpov, and A. D. Compaan

Appl. Phys. Lett. 80, 3114 (2002); http://dx.doi.org/10.1063/1.1475359 (3 pages) | Cited 5 times

Online Publication Date: 22 April 2002

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We show that external bias significantly affects the photoluminescence (PL) in CdTe photovoltaics. The main observations are: (1) reverse bias suppresses PL, (2) PL increases with moderate forward bias and tends to saturate when it is above the open-circuit voltage, and (3) PL in the region of saturation is extremely sensitive to device degradation. We attribute the observed phenomena to the competition between the field-induced separation of electrons and holes and their nonradiative recombination. We have developed a model that describes bias-dependent PL more quantitatively and forms a basis for using it as an indicator of device degradation. © 2002 American Institute of Physics.
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78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.40.+w Photoconduction and photovoltaic effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Ey III-V and II-VI semiconductors

Extremely high room-temperature two-dimensional hole gas mobility in Ge/Si0.33Ge0.67/Si(001) p-type modulation-doped heterostructures

M. Myronov, T. Irisawa, O. A. Mironov, S. Koh, Y. Shiraki, T. E. Whall, and E. H. C. Parker

Appl. Phys. Lett. 80, 3117 (2002); http://dx.doi.org/10.1063/1.1473690 (3 pages) | Cited 30 times

Online Publication Date: 22 April 2002

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To extract the room-temperature drift mobility and sheet carrier density of two-dimensional hole gas (2DHG) that form in Ge strained channels of various thicknesses in Ge/Si0.33Ge0.67/Si(001) p-type modulation-doped heterostructures, the magnetic field dependences of the magnetoresistance and Hall resistance at temperature of 295 K were measured and the technique of maximum entropy mobility spectrum analysis was applied. This technique allows a unique determination of mobility and sheet carrier density of each group of carriers present in parallel conducting multilayers semiconductor heterostructures. Extremely high room-temperature drift mobility (at sheet carrier density) of 2DHG 2940 cm2 V−1 s−1 (5.11×1011 cm−2) was obtained in a sample with a 20 nm thick Ge strained channel. © 2002 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.61.Le Other inorganic semiconductors
73.61.Cw Elemental semiconductors

Transport properties of Mn δ-doped GaAs and the effect of selective doping

Ahsan M. Nazmul, S. Sugahara, and M. Tanaka

Appl. Phys. Lett. 80, 3120 (2002); http://dx.doi.org/10.1063/1.1473878 (3 pages) | Cited 23 times

Online Publication Date: 22 April 2002

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We have grown Mn δ-doped GaAs layers on GaAs(001) substrates by molecular beam epitaxy. Secondary ion mass spectroscopy and transmission electron microscopy revealed that Mn dopants were abruptly confined. The doping profiles still retained abruptness even at elevated growth temperature up to 400 °C. Mn δ-doped GaAs samples showed high resistivity at low temperature and did not show a ferromagnetic behavior. However, in a selectively doped heterostructure (Mn δ-doped GaAs / Be-doped AlGaAs), where holes were supplied from the Be-doped AlGaAs layer, a ferromagnetic order was observed with the ferromagnetic transition temperature as high as 70 K. © 2002 American Institute of Physics.
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73.61.Ey III-V semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.72.S- Impurities in crystals
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
75.50.Pp Magnetic semiconductors

Tris-(8-hydroxyquinoline)aluminum-based organic light-emitting devices with Al/CaF2 cathode: Performance enhancement and interface electronic structures

J. Lee, Y. Park, S. K. Lee, E.-J. Cho, D. Y. Kim, H. Y. Chu, H. Lee, L.-M. Do, and T. Zyung

Appl. Phys. Lett. 80, 3123 (2002); http://dx.doi.org/10.1063/1.1474602 (3 pages) | Cited 31 times

Online Publication Date: 22 April 2002

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The device characteristics and the interface electronic structures of organic light-emitting devices based on tris-(8-hydroxyquinoline)aluminum were investigated with Al/CaF2, Al/LiF, and Al-only cathodes. Similar to the Al/LiF cathode, the Al/CaF2 cathode greatly improved the performance of the device over the Al-only cathode. However, a photoelectron spectroscopy study revealed that despite the performance improvement, the evolution of the new peaks during the Al/CaF2 cathode formation closely resembled those of the Al-only cathode rather than the Al/LiF cathode. © 2002 American Institute of Physics.
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85.60.Jb Light-emitting devices
73.20.At Surface states, band structure, electron density of states
79.60.Jv Interfaces; heterostructures; nanostructures

Spin splitting in modulation-doped AlGaN/GaN two-dimensional electron gas

K. Tsubaki, N. Maeda, T. Saitoh, and N. Kobayashi

Appl. Phys. Lett. 80, 3126 (2002); http://dx.doi.org/10.1063/1.1474599 (3 pages) | Cited 35 times

Online Publication Date: 22 April 2002

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AlGaN/GaN heterostructure devices have recently been attracting much attention because of their potential for high-performance microwave applications. Therefore, the electronic properties of a two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures have recently been discussed. We studied the magnetoresistance oscillation of the 2DEG at 0.4 K for various backgate voltages, and observed multiple oscillations resulting from spin splitting. The magnetoresistance shows clear beating due to the superposition of three oscillations. The frequency interval between the first and second largest frequencies is proportional to the total electron concentration and the measured spin-orbit interaction parameter agrees with the theoretical one. Therefore, the first and second largest frequencies are found to correspond to spin splitting by the spin-orbit interaction. © 2002 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
81.05.Ea III-V semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.25.Mk Spin transport through interfaces
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Effects of sulfur passivation on Ti/Al ohmic contacts to n-type GaN using CH3CSNH2 solution

June O Song, Seong-Ju Park, and Tae-Yeon Seong

Appl. Phys. Lett. 80, 3129 (2002); http://dx.doi.org/10.1063/1.1475773 (3 pages) | Cited 18 times

Online Publication Date: 22 April 2002

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We investigate the effect of CH3CSNH2 solution treatment on Ti/Al ohmic contacts to n-GaN:Si (3×1018 cm−3). It is shown that the sulfide treatment results in a drastic increase in the photoluminescence intensity, compared with that of the untreated sample. Current-voltage (I–V) results show that the sulfide treatment significantly improves the specific contact resistance. The annealing of the sulfide-treated sample (at 700 °C) results in a specific contact resistance of 3.1×10−6 Ω cm2. X-ray photoemission spectroscopy (XPS) results show that the Ga 2p core levels shift toward the higher-binding energy side by 0.2 eV for the sulfide-treated sample and by 0.4 eV for the annealed (sulfide-treated) sample, compared with that of the untreated one. It is further shown that the intensity of O 1s core level decreases with the sulfide treatment. Based on the I–V and XPS results, the sulfide and annealing treatment dependence of the specific contact resistance is discussed. © 2002 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.65.Rv Passivation
73.40.Ns Metal-nonmetal contacts
73.20.At Surface states, band structure, electron density of states
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
79.60.Jv Interfaces; heterostructures; nanostructures
61.72.Cc Kinetics of defect formation and annealing
73.40.Cg Contact resistance, contact potential

Zero-field spin splitting in In0.52Al0.48As/InxGa1−xAs metamorphic high-electron-mobility-transistor structures on GaAs substrates using Shubnikov–de Haas measurements

L. J. Cui, Y. P. Zeng, B. Q. Wang, Z. P. Zhu, L. Y. Lin, C. P. Jiang, S. L. Guo, and J. H. Chu

Appl. Phys. Lett. 80, 3132 (2002); http://dx.doi.org/10.1063/1.1476055 (3 pages) | Cited 10 times

Online Publication Date: 22 April 2002

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Shubnikov–de Haas measurements were carried out for In0.52Al0.48As/InxGa1−xAs metamorphic high-electron-mobility-transistor structures grown on GaAs substrates with different indium contents and/or different Si δ-doping concentrations. Zero-field (B→0) spin splitting was found in samples with stronger conduction band bending in the InGaAs well. It was shown that the dominant spin splitting mechanism is attributed to the contribution by the Rashba term. We found that zero-field spin splitting not only occurs in the ground electron subband, but also in the first excited electron subband for a sample with Si δ-doping concentration of 6×1012 cm−2. We propose that this In0.52Al0.48As/InxGa1−xAs metamorphic high-electron-mobility-transistor structure grown on GaAs may be a promising candidate spin-polarized field-effect transistors. © 2002 American Institute of Physics.
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85.30.Tv Field effect devices
85.75.Hh Spin polarized field effect transistors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
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