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23 Feb 1998

Volume 72, Issue 8, pp. 873-995

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Magnesium induced changes in the selective growth of GaN by metalorganic vapor phase epitaxy

B. Beaumont, S. Haffouz, and P. Gibart

Appl. Phys. Lett. 72, 921 (1998); http://dx.doi.org/10.1063/1.120874 (3 pages) | Cited 54 times

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Atmospheric pressure metalorganic vapor phase epitaxy is used to perform selective regrowth of GaN on a silicon nitride patterned mask, capping a GaN epitaxial layer deposited on (0001) sapphire substrate. The basic pattern is constituted by a 15 μm period hexagonal array of hexagonal openings in the mask, these openings being circumscribed into 10 μm diam circles. We investigate the effect of Mg incorporation on the growth anisotropy of the localized GaN islands by varying the ratio [Mg]/[Ga] of bis-methylcyclopentadienyl-magnesium and trimethylgallium partial pressures. Both undoped and Mg-doped GaN hexagonal pyramids, delimited by C (0001) and R (1 101) facets, are achieved with a good selectivity. It is found that the GaN growth rates VR and VC, measured in the R〈1math01〉 and C 〈0001〉 directions respectively, are drastically affected by the Mg incorporation. By adjusting the Mg partial pressure in the growth chamber, the VR/VC ratio can be increased so that the delimiting top C facet does not vanish as usually observed in undoped GaN localized growth, but by contrast expands. © 1998 American Institute of Physics.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors

Two-peak electroluminescence of porous silicon in persulphate solution

R. Q. Wang, J. J. Li, S. M. Cai, Z. F. Liu, and S. L. Zhang

Appl. Phys. Lett. 72, 924 (1998); http://dx.doi.org/10.1063/1.120619 (3 pages)

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A large blue shift of electroluminescence (EL) was achieved from oxidized n-type porous silicon (PS) in a persulphate solution under cathodic polarization. The two-peak phenomenon observed in the EL spectrum suggests that there are two types of luminescent centers located in the nanoscale silicon particles and at the surface of the oxidized PS layer, respectively. It is found that only the low-energy peak having luminescent centers in nanoscale silicon particles can be tuned by voltage, supporting the quantum confinement model. © 1998 American Institute of Physics.
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78.60.Fi Electroluminescence

Near-field scanning optical spectroscopy of an InGaN quantum well

P. A. Crowell, D. K. Young, S. Keller, E. L. Hu, and D. D. Awschalom

Appl. Phys. Lett. 72, 927 (1998); http://dx.doi.org/10.1063/1.120875 (3 pages) | Cited 26 times

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Near-field scanning optical microscopy is used to image photoluminescence (PL) in an InGaN/GaN quantum well (QW) with spatial resolution of approximately 100 nm for temperatures between 50 and 295 K. Strong (∼50%) fluctuations in the quantum well photoluminescence as well as a tenfold enhancement of deep level-related emission at lower energies occur at large (∼500 nm diam) pits in the heterostructure. Regions of smaller (∼15%) fluctuations in the QW PL are not correlated with the presence of pits. The spectrum of the QW PL shows no significant variations on the length scales probed in this experiment. We thus find no spectroscopic signature of the recombination of strongly localized carriers at temperatures above 50 K. © 1998 American Institute of Physics.
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78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
07.79.Fc Near-field scanning optical microscopes
78.55.Cr III-V semiconductors
07.79.Lh Atomic force microscopes
71.55.Eq III-V semiconductors
07.60.Rd Visible and ultraviolet spectrometers

Growth and characterization of thin Si80C20 films based upon Si4C building blocks

J. Kouvetakis, D. Chandrasekhar, and David J. Smith

Appl. Phys. Lett. 72, 930 (1998); http://dx.doi.org/10.1063/1.120876 (3 pages) | Cited 8 times

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The growth of thin Si80C20 diamond-structured material on (100)Si has been achieved using the novel C–H free, carbon source tetrasilyl methane, C(SiH3)4. The precursor decomposes at temperatures in the range 600–700 °C to give thin amorphous layers with a composition of Si0.80C0.20, which corresponds to the same relative concentrations of Si and C as in the precursor. The amorphous material is crystallized via solid-phase epitaxy by annealing at 825 °C to yield a potentially ordered structure in which Si4C tetrahedra are linked together in a three-dimensional diamond-cubic framework. Measured lattice parameters are larger than expected from Vegards’ Law, a discrepancy which is attributed to steric repulsions causing bond elongation. © 1998 American Institute of Physics.
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81.05.Hd Other semiconductors
81.15.Np Solid phase epitaxy; growth from solid phases
81.40.Gh Other heat and thermomechanical treatments

In situ monitoring of Raman scattering and photoluminescence from silicon surfaces in HF aqueous solutions

B. Ren, F. M. Liu, J. Xie, B. W. Mao, Y. B. Zu, and Z. Q. Tian

Appl. Phys. Lett. 72, 933 (1998); http://dx.doi.org/10.1063/1.120877 (3 pages) | Cited 11 times

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In situ Raman spectra of SiHx, Si–F, and Si–Si vibrations from Si surfaces in HF aqueous solutions are obtained using a highly sensitive confocal microprobe Raman system. Electrochemical roughening pretreatment and laser-assisted roughening procedure enable good quality surface Raman spectra to be obtained. The surface Raman and photoluminescence spectra from the Si surface in the etching environment and the correlation of the two types of spectra are discussed. The Raman spectroscopy is shown to have high potential in serving as an important tool for in situ investigating of Si surface bonding during the etching process. © 1998 American Institute of Physics.
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78.30.Am Elemental semiconductors and insulators
68.35.Ja Surface and interface dynamics and vibrations
78.55.Ap Elemental semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Cf Surface cleaning, etching, patterning

Influence of rapid thermal annealing on the optical properties of gallium nitride grown by gas-source molecular-beam epitaxy

X. B. Li, D. Z. Sun, J. P. Zhang, M. Y. Kong, and S. F. Yoon

Appl. Phys. Lett. 72, 936 (1998); http://dx.doi.org/10.1063/1.120878 (3 pages) | Cited 7 times

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Raman scattering, photoluminescence (PL), and nuclear reaction analysis (NRA) have been employed to investigate the effects of rapid thermal annealing (RTA) on GaN films grown on sapphire (0001) substrates by gas-source molecular-beam epitaxy. The Raman spectra showed the presence of the E2 (high) mode of GaN and shift of this mode from 572 to 568 cm−1 caused by annealing. The results showed that RTA has a significant effect on the strain relaxation caused by the lattice and thermal expansion misfit between the GaN epilayer and the substrate. The PL peak exhibited a blueshift in its energy position and a decrease in the full width at half maximum after annealing, indicating an improvement in the optical quality of the film. Furthermore, a green luminescence appeared after annealing and increased in intensity with increasing annealing time. This effect was attributed to H concentration variation in the GaN film, which was measured by NRA. A high H concentration exists in as-grown GaN, which can neutralize the deep level, and the H-bonded complex dissociates during RTA. This leads to the appearance of a luminescent peak in the PL spectrum. © 1998 American Institute of Physics.
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78.66.Fd III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
78.55.Cr III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
65.40.De Thermal expansion; thermomechanical effects
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
82.80.-d Chemical analysis and related physical methods of analysis
68.60.Bs Mechanical and acoustical properties
68.60.Dv Thermal stability; thermal effects

Deep ultraviolet enhanced wet chemical etching of gallium nitride

L.-H. Peng, C.-W. Chuang, J.-K. Ho, C.-N. Huang, and C.-Y. Chen

Appl. Phys. Lett. 72, 939 (1998); http://dx.doi.org/10.1063/1.120879 (3 pages) | Cited 52 times

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We report a study of the ultraviolet (UV) irradiation effects on the wet chemical etching of unintentionally doped n-type gallium nitride (GaN) layers grown on sapphire substrates. When illuminated with a 253.7 nm mercury line source, etching of GaN is found to take place in aqueous phosphorus acid (H3PO4) and potassium hydroxide (KOH) solutions of pH values ranging from −1 to 2 and 11 to 15, respectively. Formation of gallium oxide is observed on GaN when illuminated in dilute H3PO4 and KOH solutions. These results are attributed to a two-step reaction process upon which the UV irradiation is shown to enhance the oxidative dissolution of GaN. © 1998 American Institute of Physics.  
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81.05.Ea III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning

Gain studies of (Cd, Zn)Se quantum islands in a ZnSe matrix

M. Strassburg, V. Kutzer, U. W. Pohl, A. Hoffmann, I. Broser, N. N. Ledentsov, D. Bimberg, A. Rosenauer, U. Fischer, D. Gerthsen, I. L. Krestnikov, M. V. Maximov, P. S. Kop’ev, and Zh.I. Alferov

Appl. Phys. Lett. 72, 942 (1998); http://dx.doi.org/10.1063/1.120880 (3 pages) | Cited 88 times

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By inserting stacked sheets of nominally 0.7 monolayer CdSe into a ZnSe matrix we create a region with strong resonant excitonic absorption. This leads to an enhancement of the refractive index on the low-energy side of the absorption peak. Efficient waveguiding can thus be achieved without increasing the average refractive index of the active layer with respect to the cladding. Processed high-resolution transmission electron microscopy images show that the CdSe insertions form Cd-rich two-dimensional (Cd, Zn)Se islands with lateral sizes of about 5 nm. The islands act as quantum dots with a three-dimensional confinement for excitons. Zero-phonon gain is observed in the spectral range of excitonic and biexcitonic waveguiding. At high excitation densities excitonic gain is suppressed due to the population of the quantum dots with biexcitons. © 1998 American Institute of Physics.
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78.66.Hf II-VI semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.45.+h Stimulated emission
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.)
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
63.20.-e Phonons in crystal lattices
42.55.Px Semiconductor lasers; laser diodes

Optical characterization of GaN/SiC n-p heterojunctions and p-SiC

John T. Torvik, Chang-hua Qiu, Moeljanto Leksono, and Jacques I. Pankove

Appl. Phys. Lett. 72, 945 (1998); http://dx.doi.org/10.1063/1.120881 (3 pages) | Cited 18 times

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Optical characterization of GaN/SiC heterojunctions and p-SiC has been performed to explain the current–voltage (I–V) characteristics in GaN/SiC n-p heterojunction diodes. The I–V characteristics exhibit tunneling-assisted current with low forward “turn-on” voltages around 1.15 V as opposed to the expected drift/diffusion current with a turn on around 2.5 V. Electroluminescence (EL) measurements on these diodes revealed an infrared peak at 1.25 eV and a red peak at 1.75 eV. Photoluminescence (PL) measurements on p-SiC yielded peaks at 1.25 and 1.80 eV. Since the band gap of 6H–SiC is 3.03 eV, we attribute the EL and PL peaks to radiative transitions from the conduction band edge to a defect level and subsequently down to the valence band edge of p-SiC. This defect level is located 1.25 eV above the valence band edge. © 1998 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.60.Fi Electroluminescence
78.66.Fd III-V semiconductors
78.66.Li Other semiconductors
71.55.Ht Other nonmetals
73.40.Gk Tunneling
78.55.Hx Other solid inorganic materials

Regular step arrays on silicon

J. Viernow, J.-L. Lin, D. Y. Petrovykh, F. M. Leibsle, F. K. Men, and F. J. Himpsel

Appl. Phys. Lett. 72, 948 (1998); http://dx.doi.org/10.1063/1.120882 (3 pages) | Cited 82 times

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Highly regular arrays of steps are produced on vicinal Si(111)7×7. The step edges are atomically straight for up to 2×104 lattice sites. The terraces are single domain, which produces a minimum kink width of 2.3 nm (half a 7×7 unit cell) and thus a high barrier for creating kinks. Criteria for obtaining optimum step arrays are established, such as the miscut [≈1° towards (112)] and an annealing sequence which passes through step bunching regions quickly. © 1998 American Institute of Physics.
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81.05.Cy Elemental semiconductors
81.65.Cf Surface cleaning, etching, patterning
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments

The reaction of carbon tetrachloride with gallium arsenide (001)

L. Li, S. Gan, B.-K. Han, H. Qi, and R. F. Hicks

Appl. Phys. Lett. 72, 951 (1998); http://dx.doi.org/10.1063/1.120620 (3 pages) | Cited 5 times

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Carbon tetrachloride dissociatively adsorbs on the Ga-rich (4×2) reconstruction of GaAs (001) at 200 °C. Upon heating to 440 °C, the chlorine desorbs as GaCl, which etches the surface. Scanning tunneling micrographs reveal that this reaction transforms the (4×2) into a Ga-rich (3×2) structure that is interlaced with As-rich (2×4) phases. The (3×2) is well ordered, while the (2×4) phases exhibit a high degree of disorder. This work establishes the surface reaction pathway for carbon doping of GaAs with CCl4.© 1998 American Institute of Physics.  
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81.65.Cf Surface cleaning, etching, patterning
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Rh Phase transitions and critical phenomena
81.05.Ea III-V semiconductors
72.80.Ey III-V and II-VI semiconductors

A reflection high-energy electron diffraction and atomic force microscopy study of the chemical beam epitaxial growth of InAs and InP islands on (001) GaP

B. Junno, T. Junno, M. S. Miller, and L. Samuelson

Appl. Phys. Lett. 72, 954 (1998); http://dx.doi.org/10.1063/1.120883 (3 pages) | Cited 17 times

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We have studied the formation of strained InAs and InP island structures on GaP surfaces grown by chemical beam epitaxy. InP grows pseudomorphically for 3 ML before island crystallization is observed by reflection high-energy electron diffraction, following a typical Stranski–Krastanov growth mode. For the growth of InAs on GaP, three-dimensional diffraction peaks are observed after 0.9 ML of InAs have been deposited, indicating a Volmer–Weber growth mode. Atomic force microscopy studies of these structures are presented and the optical properties are discussed. © 1998 American Institute of Physics.
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81.05.Ea III-V semiconductors
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors

Addition energies in semiconductor quantum dots: Role of electron–electron interaction

Massimo Rontani, Fausto Rossi, Franca Manghi, and Elisa Molinari

Appl. Phys. Lett. 72, 957 (1998); http://dx.doi.org/10.1063/1.120933 (3 pages) | Cited 27 times

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We show that the addition spectra of semiconductor quantum dots in the presence of magnetic field can be studied through a theoretical scheme that allows an accurate and practical treatment of the single-particle states and electron–electron interaction up to large numbers of electrons. The calculated addition spectra exhibit the typical structures of Hund-like shell filling, and account for recent experimental findings. A full three-dimensional description of Coulomb interaction is found to be essential for predicting the conductance characteristics of few-electron semiconductor structures. © 1998 American Institute of Physics.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.23.Hk Coulomb blockade; single-electron tunneling
78.20.Ls Magneto-optical effects
78.66.-w Optical properties of specific thin films
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Realization and optical characterization of etched mirror facets in GaN cavities

F. Binet, J. Y. Duboz, N. Laurent, C. Bonnat, P. Collot, F. Hanauer, O. Briot, and R. L. Aulombard

Appl. Phys. Lett. 72, 960 (1998); http://dx.doi.org/10.1063/1.120934 (3 pages) | Cited 15 times

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We report on the realization of etched mirror facets in GaN cavities by chemically assisted ion-beam etching. The etching conditions are adjusted to obtain a high degree of verticality and smoothness. Optical pumping experiments and gain measurements are performed in etched GaN cavities of various geometries. Stimulated emission and lasing are observed. The study of the value of the gain at threshold as a function of the cavity length allows a determination of the reflection coefficient of the etched mirror. The measured value of 15% is in good agreement with the one expected for a perfect air–GaN interface. This demonstrates the high quality of the etched mirror facets. © 1998 American Institute of Physics.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes
78.45.+h Stimulated emission
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.05.Ea III-V semiconductors

Efficient all-optical light modulation in a piezoelectric heterostructure at room temperature

V. Ortiz, N. T. Pelekanos, and Guido Mula

Appl. Phys. Lett. 72, 963 (1998); http://dx.doi.org/10.1063/1.120935 (3 pages) | Cited 3 times

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We demonstrate a novel piezoelectric-barrier heterostructure designed for efficient all-optical light modulation. The modulation mechanism relies upon drastic photocarrier separation by the piezoelectric field in the barrier layers. We present room temperature results showing that an optical “control” power of 70 W/cm2 creates in the heart of the structure a space-charge field of about 30 kV/cm, which induces large spectral shifts (≈100 nm) in the photoluminescence spectra of a CdHgTe quantum well in the 1.5 μm range. © 1998 American Institute of Physics.
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78.66.Hf II-VI semiconductors
42.79.Hp Optical processors, correlators, and modulators
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.)
77.65.-j Piezoelectricity and electromechanical effects
78.55.Et II-VI semiconductors
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
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