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22 Feb 1999

Volume 74, Issue 8, pp. 1057-1183

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Band offsets at the ZnSe/CuGaSe2(001) heterointerface

A. Bauknecht, U. Blieske, T. Kampschulte, J. Albert, H. Sehnert, M. Ch. Lux-Steiner, A. Klein, and W. Jaegermann

Appl. Phys. Lett. 74, 1099 (1999); http://dx.doi.org/10.1063/1.123455 (3 pages) | Cited 14 times

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The formation of the ZnSe/CuGaSe2 heterointerface was studied by x-ray photoelectron spectroscopy (XPS). ZnSe was sequentially grown on CuGaSe2(001) epilayers. In situ photoemission spectra of the Ga 3d and Zn 3d core levels as well as XPS valence bands were acquired after each deposition step. The valence-band offset is determined to be ΔEV = 0.6±0.1 eV. As a consequence, a nearly symmetric “type-I” band alignment for the ZnSe/CuGaSe2 heterojunction with a conduction-band offset of ΔEC = 0.4±0.1 eV is found. Concerning the band alignment ZnSe can, therefore, be expected to be a suitable buffer material for CuGaSe2-based thin-film solar cells. © 1999 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
79.60.Bm Clean metal, semiconductor, and insulator surfaces
84.60.Jt Photoelectric conversion

Intermixing in strained InGaAs/GaAs quantum-well infrared photodetectors

Alex S. W. Lee, E. Herbert Li, and Gamani Karunasiri

Appl. Phys. Lett. 74, 1102 (1999); http://dx.doi.org/10.1063/1.123456 (3 pages) | Cited 3 times

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The effect of interdiffusion on strained InGaAs/GaAs quantum-well infrared photodetectors is investigated. Photoluminescence measurements of the interband transition indicate that there is minimal deterioration of the annealed heterostructures, as it is also evident from both the transverse electric and transverse magnetic infrared intersubband optical transitions. The absorption peak wavelength is redshifted from the as-grown 10.2 μm to 10.5 and 11.2 μm for 5 and 10 s annealing, respectively, at 850 °C without appreciable degradation in absorption strength. The peak responsivity of the as-grown and annealed spectra is of comparable amplitude, whereas the annealed spectra become narrower in shape. The dark current of the annealed devices is about an order of magnitude higher than the as-grown one at 77 K. © 1999 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
61.72.Cc Kinetics of defect formation and annealing

Observation of tip-induced gap states in lightly doped Si(100) using scanning tunneling spectroscopy

Hai-An Lin, Ralph J. Jaccodine, and Michael S. Freund

Appl. Phys. Lett. 74, 1105 (1999); http://dx.doi.org/10.1063/1.123457 (3 pages) | Cited 2 times

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Scanning tunneling spectroscopy without shifts related to band bending was utilized to study tip-induced gap states in lightly doped Si(100) (ρ=12–25 Ω cm). The separation dependence of scanning tunneling spectroscopy revealed a reversible interaction between the tip and sample. A “U” shape curve of normalized differential conductivity versus sample bias in the band gap was also observed as the tip approached the sample, suggesting the evolution of a continuum of tip-induced gap states. These results can be explained in terms of an emission dominant-tunnel model where the tunneling current is controlled by electron emission from traps in the band gap. The experiments described herein demonstrate that scanning tunneling microscopy can be used as a powerful tool for probing the origin and evolution of the surface states. © 1999 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
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
73.25.+i Surface conductivity and carrier phenomena
73.40.Ns Metal-nonmetal contacts
71.20.Mq Elemental semiconductors
72.80.Cw Elemental semiconductors

Determination of energy levels of surface states in GaAs metal–semiconductor field-effect transistor using deep-level transient spectroscopy

Kyoung Jin Choi and Jong-Lam Lee

Appl. Phys. Lett. 74, 1108 (1999); http://dx.doi.org/10.1063/1.123458 (3 pages) | Cited 9 times

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The energy levels of surface states at the surface of GaAs were determined through capacitance deep-level transient spectroscopy of GaAs metal–semiconductor field-effect transistor with large gate periphery. Two types of hole-like traps are observed in the spectra. These originate from the surface states at the ungated regions between gate and source/drain electrodes. The activation energies of both surface states are determined to be 0.65±0.07 and 0.88±0.04 eV, which agree well with the energy levels of AsGa+ and AsGa++ within band gap of GaAs, responsible for the Fermi level pinning at the surface. © 1999 American Institute of Physics.
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85.30.Tv Field effect devices
73.20.At Surface states, band structure, electron density of states
73.20.Hb Impurity and defect levels; energy states of adsorbed species
71.55.Eq III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
85.30.De Semiconductor-device characterization, design, and modeling

A narrow photoluminescence linewidth of 21 meV at 1.35 μm from strain-reduced InAs quantum dots covered by In0.2Ga0.8As grown on GaAs substrates

Kenichi Nishi, Hideaki Saito, Shigeo Sugou, and Jeong-Sik Lee

Appl. Phys. Lett. 74, 1111 (1999); http://dx.doi.org/10.1063/1.123459 (3 pages) | Cited 250 times

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InAs quantum dots with size fluctuations of less than 4% were grown on GaAs using the self-assembling method. By covering the quantum dots with In0.2Ga0.8As or In0.2Al0.8As, strain in InAs dots can be partly reduced due to relaxation of lattice constraint in the growth direction. This results in low-energy emission (about 1.3 μm) from the quantum dots. The photoluminescence linewidth can be reduced to 21 meV at room temperature. This width is completely comparable to the theoretical limit of a band-to-band emission from a quantum well at room temperature. Because the dots can be uniformly covered by the strain reducing layers, factors that degrade size uniformity during coverage, such as compositional mixing or segregation, will be suppressed, allowing for an almost ideal buried quantum dot structure. © 1999 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Depth profiling of GaN by cathodoluminescence microanalysis

K. Fleischer, M. Toth, M. R. Phillips, J. Zou, G. Li, and S. J. Chua

Appl. Phys. Lett. 74, 1114 (1999); http://dx.doi.org/10.1063/1.123460 (3 pages) | Cited 35 times

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We present the results of a depth-resolved cathodoluminescence (CL) and transmission electron microscopy study of autodoped GaN grown on sapphire. Depth-resolved CL analysis can be used for depth profiling of the yellow luminescence (YL) center concentration which was found to increase with depth. The results are consistent with the (ON–VGa)2− complex model of YL centers [J. Neugebauer and C. G. Van de Walle, Appl. Phys. Lett. 69, 503 (1996) and T. Mattila and R. M. Nieminen, Phys. Rev. B 55, 9571 (1996)]. Depth profiling of the near-edge emission in GaN layers thicker than ∼0.5 μm is not possible due to strong self-absorption. © 1999 American Institute of Physics.
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71.55.Eq III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence

Valence-band structure of wurtzite GaN including the spin-orbit interaction

G. B. Ren, Y. M. Liu, and P. Blood

Appl. Phys. Lett. 74, 1117 (1999); http://dx.doi.org/10.1063/1.123461 (3 pages) | Cited 31 times

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We have investigated the effects of the spin-orbit interaction on the valence-band structure of wurtzite GaN in the k⋅p theory. The spin-orbit interaction is usually neglected in nitrides, which leads to three doubly degenerate bands: the heavy-hole, light-hole, and crystal-field split-off bands. Including the spin-orbit interaction, this degeneracy is removed to give six single bands. We obtained the Luttinger-like parameters in bulk wurtzite GaN by fitting data obtained from an empirical pseudopotential calculation obtaining a value for the parameter A7 of 93.7 meV/Å. We also used these results to calculate the valence-band structures of a GaN/AlGaN quantum well. Our result shows the spin-orbit interaction is important in GaN and associated quantum well structures. © 1999 American Institute of Physics.
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71.20.Nr Semiconductor compounds
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.70.Ch Crystal and ligand fields
71.15.Dx Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)

Direct observation of traps responsible for positive space charge in alternating-current thin-film electroluminescent devices

Alex N. Krasnov

Appl. Phys. Lett. 74, 1120 (1999); http://dx.doi.org/10.1063/1.123462 (3 pages) | Cited 4 times

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Space charge has significant influence on the operation of alternating-current thin-film electroluminescent displays. This letter introduces a relatively simple method for direct observation of the distribution of traps responsible for the space charge in the active layer of the devices. Contribution of native and dopant defects in the space charge formation is discussed. © 1999 American Institute of Physics.
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85.60.Pg Display systems
42.79.Kr Display devices, liquid-crystal devices
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
77.22.Jp Dielectric breakdown and space-charge effects
71.55.-i Impurity and defect levels

Dry etching of GaN substrates for high-quality homoepitaxy

M. Schauler, F. Eberhard, C. Kirchner, V. Schwegler, A. Pelzmann, M. Kamp, K. J. Ebeling, F. Bertram, T. Riemann, J. Christen, P. Prystawko, M. Leszczynski, I. Grzegory, and S. Porowski

Appl. Phys. Lett. 74, 1123 (1999); http://dx.doi.org/10.1063/1.123463 (3 pages) | Cited 18 times

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Chemically assisted ion-beam etching (CAIBE) was used to remove subsurface damage from polished GaN bulk substrates prior to growth. Subsequently, GaN layers were deposited by metalorganic vapor phase epitaxy. Only the CAIBE-treated areas reveal a mirror-like surface without trenches, scratches, or holes. A dramatic increase of crystal quality is determined by low-temperature cathodoluminescence (CL). Compared to not CAIBE-treated material, the CL intensity is improved by a factor of 1000 and the linewidth is ten times narrower. © 1999 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
78.66.Fd III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.60.Hk Cathodoluminescence, ionoluminescence

On the origin of tunneling barriers in silicon single electron and single hole transistors

Hiroki Ishikuro and Toshiro Hiramoto

Appl. Phys. Lett. 74, 1126 (1999); http://dx.doi.org/10.1063/1.123464 (3 pages) | Cited 31 times

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To clarify the channel potential profiles, Coulomb blockades of single electron and single hole tunneling in Si nanosize narrow channel metal–oxide–semiconductor field-effect transistors are intensively studied. Devices with both n+ and p+ source/drain contacts were fabricated on silicon-on-insulator substrates. Transport properties of a hole system as well as an electron system induced in the same channel were investigated. It is found from the experimental results that potential fluctuations in the channel act as tunnel barriers for both electrons and holes. Lateral quantum confinement effects or silicon oxide (SiOx) are thought to be the cause of tunnel barriers. © 1999 American Institute of Physics.
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85.35.Gv Single electron devices
85.30.Tv Field effect devices
73.23.Hk Coulomb blockade; single-electron tunneling
85.35.Ds Quantum interference devices

Visible cathodoluminescence of GaN doped with Dy, Er, and Tm

H. J. Lozykowski, W. M. Jadwisienczak, and I. Brown

Appl. Phys. Lett. 74, 1129 (1999); http://dx.doi.org/10.1063/1.123465 (3 pages) | Cited 105 times

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We reported the observation of visible cathodoluminescence of rare-earth Dy, Er, and Tm implanted in GaN. The implanted samples were given isochronal thermal annealing treatments at a temperature of 1100 °C in N2 or NH3, at atmospheric pressure to recover implantation damages and activated the rare-earth ions. The sharp characteristic emission lines corresponding to Dy3+, Er3+, and Tm3+ intra-4fn-shell transitions are resolved in the spectral range from 380 to 1000 nm, and observed over the temperature range of 8.5–411 K. The cathodoluminescence emission is only weakly temperature dependent. The results indicate that rare-earth-doped GaN epilayers are suitable as a material for visible optoelectronic devices. © 1999 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Fd III-V semiconductors
61.72.uj III-V and II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing

Temperature- and field-dependent electron and hole mobilities in polymer light-emitting diodes

L. Bozano, S. A. Carter, J. C. Scott, G. G. Malliaras, and P. J. Brock

Appl. Phys. Lett. 74, 1132 (1999); http://dx.doi.org/10.1063/1.123959 (3 pages) | Cited 185 times

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We have studied the transport properties of electron- and hole-dominated MEH-PPV, poly(2-methoxy,5-(2′-ethyl-hexoxy)-p-phenylene vinylene), devices in the trap-free limit and have derived the temperature-dependent electron and hole mobilities (μ = μ0eγ√E) from the space-charge-limited behavior at high electric fields. Both the zero-field mobility μ0 and electric-field coefficient γ are temperature dependent with an activation energy of the hole and electron mobility of 0.38±0.02 and 0.34±0.02 eV, respectively. At 300 K, we find a zero-field mobility μ0 on the order of 1±0.5×10−7 cm2/V s and an electric-field coefficient γ of 4.8±0.3×10−4 (m/V)1/2 for holes. For electrons, we find a μ0 an order of magnitude below that for holes but a larger γ of 7.8±0.5×10−4 (m/V)1/2. Due to the stronger field dependence of the electron mobility, the electron and hole mobilities are comparable at working voltages in the trap-free limit, applicable to thin films of MEH-PPV. © 1999 American Institute of Physics.
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73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Ph Polymers; organic compounds
85.60.Jb Light-emitting devices
73.50.Dn Low-field transport and mobility; piezoresistance

Staggered to straddling band lineups in InAs/Al(As, Sb)

S. Bhargava, H.-R. Blank, E. Hall, M. A. Chin, H. Kroemer, and V. Narayanamurti

Appl. Phys. Lett. 74, 1135 (1999); http://dx.doi.org/10.1063/1.123466 (3 pages) | Cited 9 times

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Ballistic electron emission spectroscopy (BEES) has been used to study both the conduction and valence band offsets between InAs and AlAsSb. With the addition of As to AlSb, the conduction band offset between it and InAs has been found to decrease despite the increase in the band gap. The resulting increase in the valence band causes the InAs/Al(As, Sb) band lineup to change from a staggered (type II) to a straddling (type I). Both room-temperature and low-temperature (77 K) BEES spectra have been taken to determine the band offsets. © 1999 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
71.20.Nr Semiconductor compounds
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

High efficient biexciton photoluminescence observed from single ZnCdSe quantum wells with continuous wave cold carrier generation

Yanfeng Wei, Daming Huang, Xingjun Wang, Gencai Yu, C. S. Zhu, and Xun Wang

Appl. Phys. Lett. 74, 1138 (1999); http://dx.doi.org/10.1063/1.123467 (3 pages) | Cited 4 times

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Biexciton photoluminescence was observed from single ZnCdSe quantum wells with excitation densities at least three orders of magnitudes lower than those reported in the literature. The very efficient biexciton photoluminescence is essentially due to the cold carrier generation under which the biexciton dissociation by hot carrier collision is greatly suppressed. © 1999 American Institute of Physics.
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78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.35.-y Excitons and related phenomena

Effect of ion mass on the evolution of extended defects during annealing of MeV ion-implanted p-type Si

S. Fatima, J. Wong-Leung, J. Fitz Gerald, and C. Jagadish

Appl. Phys. Lett. 74, 1141 (1999); http://dx.doi.org/10.1063/1.123468 (3 pages) | Cited 11 times

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Evolution of extended defects during annealing of MeV ion-implanted p-type Si has been characterized using deep level transient spectroscopy and transmission electron microscopy. The p-type Si was implanted with Si, Ge, and Sn ions with varying energies and doses from 5×1012 to 1×1014 cm−2 then annealed at 800 °C for 15 min. For all implanted species, the critical dose for transformation from point to extended defects has been determined. The type of extended defects formed depends upon the mass of the implanted species even though the dose was adjusted to create a similar damage distribution for all implanted species. © 1999 American Institute of Physics.
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61.72.Cc Kinetics of defect formation and annealing
61.72.uf Ge and Si
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Analysis of deep levels in a phenylenevinylene polymer by transient capacitance methods

H. L. Gomes, P. Stallinga, H. Rost, A. B. Holmes, M. G. Harrison, and R. H. Friend

Appl. Phys. Lett. 74, 1144 (1999); http://dx.doi.org/10.1063/1.123469 (3 pages) | Cited 30 times

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Transient capacitance methods were applied to the depletion region of an abrupt asymmetric n+−p junction of silicon and unintentionally doped poly[2-methoxy, 5 ethyl (2′ hexyloxy) paraphenylenevinylene] (MEH-PPV). Studies in the temperature range 100–300 K show the presence of a majority-carrier trap at 1.0 eV and two minority traps at 0.7 and 1.3 eV, respectively. There is an indication for more levels for which the activation energy could not be determined. Furthermore, admittance data reveal a bulk activation energy for conduction of 0.12 eV, suggesting the presence of an additional shallow acceptor state. © 1999 American Institute of Physics.
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73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Ph Polymers; organic compounds

Interactions between DX centers and hot electrons and holes in Al0.25Ga0.75As/GaAs heterostructure field-effect transistors

D. Dieci, C. Canali, R. Menozzi, M. Pavesi, and A. Cetronio

Appl. Phys. Lett. 74, 1147 (1999); http://dx.doi.org/10.1063/1.123493 (3 pages) | Cited 1 time

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Using power Al0.25Ga0.75As/GaAs heterostructure field-effect transistors (HFETs) and both electrical and electroluminescence measurements, we show here that while at room temperature the electron and hole capture processes at the DX centers present in the AlGaAs are in equilibrium, and therefore no charge buildup leading to drifts in the HFET characteristics may take place, under cryogenic conditions (T<100 K), where the electron and hole capture cross sections of the DX centers are very different, two competing processes of hole and hot electron capture lead to bias-dependent, negative, recoverable HFET threshold voltage shifts. © 1999 American Institute of Physics.
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85.30.Tv Field effect devices
84.40.-x Radiowave and microwave (including millimeter wave) technology
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
71.55.Eq III-V semiconductors
84.30.Jc Power electronics; power supply circuits
78.60.Fi Electroluminescence
73.50.Fq High-field and nonlinear effects

Growth and thermal stability of pseudomorphic Ge1−yCy/Ge superlattices on Ge(001)

R. Duschl, O. G. Schmidt, W. Winter, K. Eberl, M. W. Dashiell, J. Kolodzey, N. Y. Jin-Phillipp, and F. Phillipp

Appl. Phys. Lett. 74, 1150 (1999); http://dx.doi.org/10.1063/1.123470 (3 pages) | Cited 7 times

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High quality Ge/Ge1−yCy superlattices with nominal carbon contents of 1.2% and 2.1% were grown by molecular beam epitaxy on Ge(001). In transmission electron microscopy the layers are planar and perfectly pseudomorphic without any extended defects observable. The infrared absorption line at 529 cm−1 is attributed to the local vibrational mode of substitutional carbon in germanium. However, in contrast to Si1−yCy alloys where almost 100% of the C is substitutional under optimized growth conditions, x-ray diffraction measurements indicate that the efficiency of carbon incorporation onto substitutional sites is only about 30% for low temperature growth at TS = 200 °C. It reduces further for higher growth temperatures to only about 10% at TS = 300 °C. Post-growth annealing experiments indicate thermal stability up to 450 °C. Annealing at higher temperature results in a reduction of substitutional carbon content. As in the case of Si1−yCy alloys the built-in strain is relaxed by C diffusion and not by nucleation of misfit dislocation. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.66.Li Other semiconductors
78.30.Hv Other nonmetallic inorganics

Spiral growth of InGaN/InGaN quantum wells due to Si doping in the barrier layers

Kenji Uchida, Tao Tang, Shigeo Goto, Tomoyoshi Mishima, Atsuko Niwa, and Jun Gotoh

Appl. Phys. Lett. 74, 1153 (1999); http://dx.doi.org/10.1063/1.123471 (3 pages) | Cited 13 times

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Show Abstract
We have examined Si-doping effects in InGaN/InGaN quantum-well (QW) structures, especially the influence of Si-doped InGaN barrier layers on the growth mechanism of QW structures, by atomic force microscopy (AFM) and by photoluminescence (PL) and cathodoluminescence (CL) spectroscopy. Our AFM observations revealed that Si-doped InGaN barriers strongly affect the growth mode of overlying InGaN QW layers. This effect leads to the formation of nanoscale islands (with a density of 108 cm−2) due to spiral growth of the QW layers. The spirally grown nanoscale islands significantly increase the PL intensity. Through spatially resolved CL observations, we found that the number of dot-like CL bright spots increased dramatically when the barrier layers were Si doped, and the increased density of the spots was in good agreement with the increased density of the nanoscale islands observed by AFM. By combining these results, we show that the spirally grown QW structures produced by Si doping of the barriers effectively reduce the fluctuation of the band-gap potential in InGaN QW layers. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
81.05.Ea III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
61.72.uj III-V and II-VI semiconductors
85.40.Ry Impurity doping, diffusion and ion implantation technology
78.60.Hk Cathodoluminescence, ionoluminescence
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