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21 Aug 2000

Volume 77, Issue 8, pp. 1071-1232

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Acceptor reactivation kinetics in heavily carbon-doped GaAs epitaxial layers

J. Mimila-Arroyo and S. W. Bland

Appl. Phys. Lett. 77, 1164 (2000); http://dx.doi.org/10.1063/1.1289268 (3 pages) | Cited 8 times

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The reactivation kinetics of the acceptor behavior of carbon in GaAs layers has been studied. The reactivation was achieved by ex situ rapid thermal annealing. To follow the carbon reactivation process, a multistage annealing experiment was performed, with changes in the sample carrier concentration monitored at each stage. An analysis of these data indicates that carbon reactivation follows a first-order kinetics process that can be explained by a model which includes the effects of dopant repassivation by hydrogen retrapping during hydrogen out-diffusion, and a dependence of the attempt frequency with the carbon concentration. The reactivation occurs with an activation energy of 1.41 eV. © 2000 American Institute of Physics.
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73.61.Ey III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
81.05.Ea III-V semiconductors

Observation of resonant tunneling through a quantized state in InP quantum dots in a double-barrier heterostructure

C. V. Reddy, V. Narayanamurti, J. H. Ryou, U. Chowdhury, and R. D. Dupuis

Appl. Phys. Lett. 77, 1167 (2000); http://dx.doi.org/10.1063/1.1289264 (3 pages) | Cited 8 times

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A direct spectroscopic signature associated with the quantized state of the charge carriers in three-dimensionally confined InP quantum dots (QDs) is reported using a ballistic electron emission microscopy (BEEM)/spectroscopy technique. The self-assembled InP QDs are sandwiched in an AlInP double-barrier heterostructure. The excellent nanometer-scale lateral resolution of the BEEM technique is used to investigate the current transport mechanism by the direct injection of electrons into a single quantum dot. The BEEM spectra taken on and off the dot revealed the presence of a localized state at around 0.1±0.02 eV above the ground state. © 2000 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Ey III-V semiconductors
73.23.Hk Coulomb blockade; single-electron tunneling

Barrier-width dependence of quantum efficiencies of GaN/AlxGa1−xN multiple quantum wells

Eun-joo Shin, J. Li, J. Y. Lin, and H. X. Jiang

Appl. Phys. Lett. 77, 1170 (2000); http://dx.doi.org/10.1063/1.1289262 (3 pages) | Cited 11 times

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We present the results of picosecond time-resolved photoluminescence (PL) measurements for a set of 30 Å well GaN/AlxGa1−xN (x ∼ 0.2) multiple-quantum-well (MQW) structures with varying barrier widths LB from 30 to 100 Å, grown by metalorganic chemical-vapor deposition. The PL quantum efficiency and the recombination lifetime of these MQWs were observed to increase monotonously with an increase of the barrier width up to 80 Å. These behaviors were explained by considering two distinct mechanisms that control the radiative recombination efficiencies in MQWs. When the barrier width is below the critical thickness, the nonradiative recombination rate increases with a decrease of the barrier width due to enhanced probabilities of the electron and hole wave functions at the interfaces as well as in the AlGaN barriers. On the other hand, the misfit dislocation density increases as the barrier width approaches the critical thickness, which can result in an enhanced nonradiative interface recombination rate. Our studies here have shown that the optimal GaN/AlGaN (x ∼ 0.2) MQW structures for UV light-emitter applications are those with barrier widths ranging from 40 to 80 Å. © 2000 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
73.61.Ey III-V semiconductors
81.05.Ea III-V semiconductors
73.25.+i Surface conductivity and carrier phenomena
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.47.-p Spectroscopy of solid state dynamics

Electrical measurements on p+–p−–p+ homoepitaxial diamond capacitors

Takashi Inushima, Takahiro Matsushita, Rinat F. Mamin, Seishirou Ohya, and Hiromu Shiomi

Appl. Phys. Lett. 77, 1173 (2000); http://dx.doi.org/10.1063/1.1289270 (3 pages) | Cited 3 times

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Conductance versus voltage and capacitance versus voltage (C–V) characteristics are investigated for p+–p−–p+ capacitors over a temperature range of 40–300 K, where the p+ layer is heavily doped homoepitaxial diamond and has impurity-band conduction and the p− layer is slightly doped with valence-band conduction. Above 200 K, the capacitors behave like a semiconductor–insulator–semiconductor diode with interface barrier height of about 0.07 eV. The C–V curve agrees closely with the standard theory of semiconductor–insulator–semiconductor structure and shows formation of the deletion layer at the p+ layer on the interface. The Cole–Cole plot of conductance versus susceptance reveals that there is a virtual trap level in the p− layer which is located about 0.06 eV above the valence band. © 2000 American Institute of Physics.
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73.61.Cw Elemental semiconductors
84.32.Tt Capacitors

Growth temperature dependence of transport properties of InAs epilayers grown on GaP

Victor Souw, V. Gopal, E.-H. Chen, E. P. Kvam, M. McElfresh, and J. M. Woodall

Appl. Phys. Lett. 77, 1176 (2000); http://dx.doi.org/10.1063/1.1289269 (3 pages) | Cited 2 times

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Undoped InAs was grown by molecular-beam epitaxy directly on GaP at a set of different substrate temperatures. Transport properties were characterized by means of Hall-effect and resistivity measurements at temperatures between 3 and 300 K. It was observed that samples grown at higher temperatures had lower carrier concentrations, consistent with a decrease of ionized defects. In addition, samples grown at higher temperatures also had higher mobility, consistent with a smaller number of scattering centers. Samples grown at higher temperatures also showed much higher sensitivity of the mobility to the measurement temperature, suggesting a drop in neutral scattering defects. Transmission electron microscopy showed that the samples grown at higher temperatures had a significantly different dislocation microstructure. The observed dislocation microstructure is consistent with the mechanisms proposed for the influence of growth temperature on the variation of carrier concentration and mobility. © 2000 American Institute of Physics.
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73.61.Ey III-V semiconductors
72.80.Ey III-V and II-VI semiconductors
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
72.20.Ee Mobility edges; hopping transport
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Lk Linear defects: dislocations, disclinations
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Single-electron tunneling study of two-dimensional gold clusters

Bing Wang, Xudong Xiao, Xianxiang Huang, Ping Sheng, and J. G. Hou

Appl. Phys. Lett. 77, 1179 (2000); http://dx.doi.org/10.1063/1.1289500 (3 pages) | Cited 25 times

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By using scanning tunneling microscopy/spectroscopy, we have studied the current–voltage characteristics of two-dimensional (2D) Au clusters, thermally deposited on self-assembled alkanethiol monolayer. The curves display Coulomb blockade and staircase with asymmetric behavior. The measured zero conductance gap as a function of cluster size is in excellent agreement with classical model calculations, in which the 2D Au island is treated as metallic in the planar direction but nonmetallic in the normal direction. © 2000 American Institute of Physics.
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73.23.Hk Coulomb blockade; single-electron tunneling
73.22.-f Electronic structure of nanoscale materials and related systems
73.61.At Metal and metallic alloys

Quantum confinement in germanium nanocrystals

Y. M. Niquet, G. Allan, C. Delerue, and M. Lannoo

Appl. Phys. Lett. 77, 1182 (2000); http://dx.doi.org/10.1063/1.1289659 (3 pages) | Cited 122 times

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The electronic structure of Ge nanocrystals is studied using a sp3 tight binding description. Analytical laws for the confinement energies, valid over the whole range of sizes, are derived. We validate our results with ab initio calculations in the local density approximation for smaller clusters. Comparing to experimental data, we conclude that, similar to the case of silicon: (a) the blue-green photoluminescence (PL) of Ge nanocrystals comes from defects in the oxide and (b) the size dependent PL in the near infrared probably involves a deep trap in the gap of the nanocrystals. We predict that the radiative lifetimes remain long in spite of the small difference (0.14 eV) between direct and indirect gaps of bulk Ge. © 2000 American Institute of Physics.
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71.55.Cn Elemental semiconductors
73.22.-f Electronic structure of nanoscale materials and related systems
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
78.55.Ap Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)

Hot hole relaxation dynamics in p-GaN

Hong Ye, G. W. Wicks, and P. M. Fauchet

Appl. Phys. Lett. 77, 1185 (2000); http://dx.doi.org/10.1063/1.1289651 (3 pages) | Cited 13 times

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The hot hole relaxation dynamics is studied in a Mg-doped p-type GaN film grown by molecular-beam epitaxy on sapphire. A nondegenerate femtosecond pump-probe technique is used, in which the holes are excited by an infrared pump and the hole dynamics is monitored by a tunable near ultraviolet probe. Complex transients, showing bleaching or induced absorption, are observed. A hot hole energy relaxation time of 0.6 ps has been obtained. Modeling suggests that longitudinal optical phonon emission modified by hot phonon effects is the dominant energy relaxation process. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
63.20.-e Phonons in crystal lattices
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency

The effect of back channel hydrogen plasma treatment on the electrical characteristics of amorphous thin film transistors

S. G. Kang, S. C. Bae, and S. Y. Choi

Appl. Phys. Lett. 77, 1188 (2000); http://dx.doi.org/10.1063/1.1289657 (3 pages) | Cited 1 time

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This letter reports that hydrogen plasma treatments on the back channel of thin film transistors are an effective way to improve the off-current characteristics. The effects of the hydrogen plasma treatments on the amorphous Si were checked using current–voltage plotter, atomic force microscopy, and secondary ion mass spectrometry. The surface of the amorphous Si was etched and passivated by the hydrogen radicals at various radio-frequency (rf) powers. The resistance of the modulated back channel increased and the off-current characteristic was improved from 530 to 1.68 pA, which was caused by the increase of roughness and hydrogen contents at back channel as a function of rf power. © 2000 American Institute of Physics.
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85.30.Tv Field effect devices
81.05.Gc Amorphous semiconductors
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
68.35.B- Structure of clean surfaces (and surface reconstruction)
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.05.Cy Elemental semiconductors
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
81.65.Cf Surface cleaning, etching, patterning
81.65.Rv Passivation
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