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19 Dec 1994

Volume 65, Issue 25, pp. 3167-3289

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Double‐disk structure for output coupling in microdisk lasers

D. Y. Chu, M. K. Chin, W. G. Bi, H. Q. Hou, C. W. Tu, and S. T. Ho

Appl. Phys. Lett. 65, 3167 (1994); http://dx.doi.org/10.1063/1.112470 (3 pages) | Cited 28 times

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We report our experiment on the use of a double‐disk structure to couple light output from a microdisk laser which allows us to maintain a high Q value of the microdisk resonator. The small photon leakage rate from the lower lasing disk to the top waveguiding disk can be carefully controlled by choosing the distance between the two disks. Various structures can be fabricated on the top disk to couple the light out. In this letter, a simple opening in the top disk is used for output coupling. © 1994 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation

Gain coupled distributed feedback lasers realized by masked implantation enhanced intermixing

C. Kaden, H.‐P. Gauggel, V. Hofsäss, A. Hase, H. Schweizer, and H. Künzel

Appl. Phys. Lett. 65, 3170 (1994); http://dx.doi.org/10.1063/1.112471 (3 pages) | Cited 1 time

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Long wavelength 1.3 μm gain coupled distributed feedback (GC‐DFB) lasers were realized by masked implantation enhanced intermixing. On the basis of this full planar technology GC‐DFB lasers with first and second order gratings were fabricated in the InGaAs/InGaAlAs system. The lasers show clear GC‐DFB laser emission with a single mode yield of 69% and remain single mode up to several times laser threshold. The results are in good agreement with the theoretical description of our gain coupled lasers by optical matrix theory. © 1994 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation
61.80.Jh Ion radiation effects

Modes in optical waveguides formed by diffusion revisited

Zhen Ye

Appl. Phys. Lett. 65, 3173 (1994); http://dx.doi.org/10.1063/1.112472 (3 pages) | Cited 3 times

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For an optical waveguide with index of refractive having a small exponential variation superimposed on a constant background value, the wave equation can be solved exactly. It is shown that the characteristic equation determining the optical modes can be solved in an uncomplicated form. The number of normal modes depends on the waveguide properties through a simple equation. © 1994 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Enhancement of second harmonic generation at 1.06 μm using a quasi‐phase‐matched AlGaAs/GaAs asymmetric quantum well structure

Xiaohua H. Qu, Harry Ruda, Siegfried Janz, and Anthony J. SpringThorpe

Appl. Phys. Lett. 65, 3176 (1994); http://dx.doi.org/10.1063/1.112958 (3 pages) | Cited 6 times

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We report on the observation of a significant enhancement of second harmonic generation (SHG) in reflection mode using multiple GaAs/AlxGa1−xAs asymmetric quantum wells (AQWs). The growth sequence and spacing of these AQWs were carefully designed for quasi‐phase‐matching of SHG using 1.06 μm fundamental wavelength pumping. The maximum SHG measured from this AQW sample is approximately twice that of an undoped semi‐insulating GaAs reference sample. This represents a 2.6 times enhancement after allowing for the cap layer absorption of the SH signal from AQWs. The SH susceptibility of a single AQW is then estimated as ‖χ(2)24,QW‖=1.3×10−11 m/V and ‖χ(2)32,QW‖=1.1×10−11 m/V, which are in excellent agreement with results of our theoretical modeling. © 1994 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.66.Fd III-V semiconductors

Very low loss channel waveguides in polymethylmethacrylate

Anadi Mukherjee, Ben Joy Eapen, and Swapan K. Baral

Appl. Phys. Lett. 65, 3179 (1994); http://dx.doi.org/10.1063/1.112473 (3 pages) | Cited 7 times

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A unique ultraviolet laser fabrication technique of very low loss channel waveguides in polymethylmethacrylate (PMMA) is reported. Beside low surface and sidewall scattering, the role of bulk scattering in polymeric waveguides was addressed. Linear propagation loss of 0.08 dB/cm in channel waveguides of PMMA at 633 nm was achieved. The experimentally observed one order of magnitude reduction of linear loss due to a selection of maximum size polymers used is qualitatively explained from Mie scattering simulation from bulk polymer medium. This points to the possibility of further reduction of linear propagation loss in polymeric waveguides with reduced dimension of constituent polymers. © 1994 American Institute of Physics.
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42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers
42.70.Jk Polymers and organics
42.82.Cr Fabrication techniques; lithography, pattern transfer

Strontium and SrO epitaxy on hydrogen‐terminated Si(111)

Akihiko Hirata, Koichiro Saiki, and Atsushi Koma

Appl. Phys. Lett. 65, 3182 (1994); http://dx.doi.org/10.1063/1.112474 (3 pages) | Cited 7 times

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Epitaxy of Sr and SrO films onto hydrogen‐terminated Si (111) has been demonstrated. The use of hydrogen‐terminated Si (111) has enabled the epitaxy of metallic Sr films, whereas direct epitaxy on a clean 7×7 Si (111) surface has not been successful. The alternate supply of Sr and O during growth has made it possible to grow good epitaxial SrO films. It has been revealed by electron energy loss spectroscopy that stoichiometric SrO films are obtained by this method. © 1994 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.Fx Diffusion; interface formation

Low‐temperature plasma enhanced chemical vapor deposition of SiO2

Shashank C. Deshmukh and Eray S. Aydil

Appl. Phys. Lett. 65, 3185 (1994); http://dx.doi.org/10.1063/1.112475 (3 pages) | Cited 27 times

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Silicon dioxide (SiO2) films, with qualities approaching to those of thermal oxide, were deposited at 40 °C in a helical resonator plasma reactor from tetraethylorthosilicate (TEOS) and oxygen discharge. The films were characterized using transmission infrared spectroscopy, variable angle spectroscopic ellisometry, and wet etch rate measurements. It was found that the TEOS/O2 ratio, @FR, in plasma enhanced chemical vapor deposition of SiO2 is as important a parameter as the substrate temperature. Using low TEOS/O2 ratio (@FR<1:20), high quality SiO2 films could be deposited by PECVD at room temperature. At high TEOS/O2 ratio, particularly at low temperature, ethoxy ligands of the TEOS molecule are incorporated into the film disrupting the connectedness of the SiO4 tetrahedra resulting in porous, low density films with high OH content. © 1994 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Pulsed laser deposition of VO2 thin films

D. H. Kim and H. S. Kwok

Appl. Phys. Lett. 65, 3188 (1994); http://dx.doi.org/10.1063/1.112476 (3 pages) | Cited 67 times

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High quality vanadium dioxide (VO2) thin films have been successfully deposited by pulsed laser deposition without postannealing on (0001) and (1010) sapphire substrates. X‐ray diffraction reveals that the films are highly oriented with (010) planes parallel to the surface of the substrate. VO2 thin films on (0001) and (1010) substrates show semiconductor to metal transistions with electrical resistance changes as large as 4×104, 105, respectively. Thin films on (1010) substrate have a transition at as low as 55 °C with a hysteresis less than 1 °C. These transition properties are comparable with single crystal VO2. © 1994 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
73.61.Ng Insulators

Thermodynamic guidance for implantation treatments to improve coating–substrate adhesion

I. L. Singer, S. Fayeulle, P. D. Ehni, and R. G. Vardiman

Appl. Phys. Lett. 65, 3191 (1994); http://dx.doi.org/10.1063/1.112477 (3 pages)

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A novel ‘‘seeding’’ method is disclosed, in which ion implanted Al atoms promote bonding between SiC and a subsequently deposited Al2O3 coating. Al+ ions were implanted in SiC substrates near room temperature to a fluence of 4×1017 Al/cm2 at an energy of 110 keV. The substrates were coated with 100–200 nm of aluminum oxide and then heated in air (i.e., oxidized) for 4 hours at temperatures from 500 to 1000 °C. Scratch tests demonstrated that coatings spalled from nonimplanted substrates but not from Al+‐implanted substrates. Auger sputter depth profiles of substrates oxidized at 850 °C showed that Al diffused out of the implanted layer and an Al‐Si‐O layer formed at the coating‐substrate interface. Cross‐section and plan TEM of a substrate oxidized at 1000 °C identified the interface phase as mullite and found fine‐grained SiC and mullite (Al6Si2O13) in the implanted layer. The composition and phase changes were explained in terms of the thermochemical reactions expected of the Al‐Al2O3‐SiC‐O2 system. © 1994 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
68.55.-a Thin film structure and morphology
61.80.Jh Ion radiation effects
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Ion‐implantation induced interdiffusion in CdTe/CdMgTe quantum wells

D. Tönnies, G. Bacher, D. Eisert, A. Forchel, A. Waag, Th. Litz, and G. Landwehr

Appl. Phys. Lett. 65, 3194 (1994); http://dx.doi.org/10.1063/1.112439 (3 pages) | Cited 3 times

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The influence of ion implantation on the interdiffusion of Cd and Mg in CdTe/CdMgTe single quantum wells was studied. The samples were implanted with 150 keV Ar+ ions and subsequently annealed for 1 min by rapid thermal annealing at temperatures between 400 and 480 °C. Ion implantation and annealing lead to an intermixing of barrier and well material, causing a blue shift of the characteristic emission spectrum. The dependence of the energy shift on the ion dose and the annealing temperature was studied. For an ion dose of 1×1014 cm−2 and an annealing temperature of 400 °C a blueshift of 80 meV compared to a nonimplanted reference sample indicates a significant enhancement of the interdiffusion of Cd and Mg by the implantation. © 1994 American Institute of Physics.
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61.80.Jh Ion radiation effects
66.30.Ny Chemical interdiffusion; diffusion barriers
78.66.Hf II-VI semiconductors
68.35.Fx Diffusion; interface formation

Topmost surface analysis of SrTiO3 (001) by coaxial impact‐collision ion scattering spectroscopy

M. Yoshimoto, T. Maeda, K. Shimozono, H. Koinuma, M. Shinohara, O. Ishiyama, and F. Ohtani

Appl. Phys. Lett. 65, 3197 (1994); http://dx.doi.org/10.1063/1.112988 (3 pages) | Cited 50 times

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The terminating atomic plane of SrTiO3 (001) surface was investigated by means of coaxial impact‐collision ion scattering spectroscopy (CAICISS). CAICISS spectra proved that SrTiO3 (001) surfaces of as‐supplied substrates as well as of O2‐annealed substrates were predominantly terminated with TiO2 atomic plane, while the SrO atomic plane came at the topmost surface of SrTiO3 (001) homoepitaxial film. This indicates the structural conversion of the topmost atomic layer from TiO2 to SrO occurred during the SrTiO3 homoepitaxial growth. The azimuth rotational CAICISS spectra exhibited a fourfold symmetry in the surface atom alignments, showing the square lattice structure of a terminating plane. © 1994 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
74.78.-w Superconducting films and low-dimensional structures

Thermal stability and electrical properties of hydrogenated amorphous carbon film

A. Callegari, D. A. Buchanan, H. Hovel, E. Simonyi, A. Marwick, and N. E. Lustig

Appl. Phys. Lett. 65, 3200 (1994); http://dx.doi.org/10.1063/1.112440 (3 pages) | Cited 6 times

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The thermal stability of a plasma‐deposited amorphous carbon film was enhanced by using acetylene heavily diluted with He. The film preserved its hardness even after annealing at ≂590  °C in Ar/H2, while a film deposited in similar conditions in an acetylene/Ar mixture softened significantly. The I‐V characteristics of n‐ and p‐type Si/amorphous carbon heterojunctions showed a 0.2 eV discrepancy. This is attributed to an offset in the conduction band of the amorphous carbon with respect to Si. © 1994 American Institute of Physics.
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68.60.Dv Thermal stability; thermal effects
73.61.Jc Amorphous semiconductors; glasses
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Structural study of diamond film formed on silicon wafer by hot‐filament chemical vapor deposition method

Jie Yang, Zhangda Lin, Li‐Xin Wang, Sing Jin, and Zhe Zhang

Appl. Phys. Lett. 65, 3203 (1994); http://dx.doi.org/10.1063/1.112413 (3 pages) | Cited 21 times

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Very important evidence has been obtained by high‐resolution cross‐sectional electron microscopy (HREM) that diamond films prepared by the hot‐filament chemical vapor deposition (HFCVD) method were grown epitaxially on the mirror‐polished Si(100) substrate in a local area with surface biasing pretreatment. There is about a 7.3° angle between Si (100) and D(100) heteroepitaxial crystalline planes. The same type of twinnings (coherent twin boundaries of type, Σ=3) exist on and near the interface. High preferential oriented diamond films have been observed by scanning electron microscopy (SEM). From the discussion, the pretreatment of the substrate is a key factor for the heteroepitaxy of diamond on Si wafer. © 1994 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology

Improved microscratch hardness of ion‐plated carbon film by nitrogen inclusion evaluated by atomic force microscope

S. Miyake, S. Watanabe, H. Miyazawa, M. Murakawa, R. Kaneko, and T. Miyamoto

Appl. Phys. Lett. 65, 3206 (1994); http://dx.doi.org/10.1063/1.112414 (3 pages) | Cited 17 times

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Nitrogen‐containing carbon films where deposited by reactive ion plating under a pure nitrogen ambient. Knoop hardness, microindentation hardness, and microscratch hardness of these films were evaluated. Indentation hardness, such as Knoop hardness and microindentation hardness, is influenced by surface roughness and substrate hardness, so the effect of nitrogen inclusion on the hardness cannot be clearly evaluated. In contrast, an atomic force microscope can clearly evaluate the effect of nitrogen inclusion on scratched wear depth. © 1994 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
68.35.Gy Mechanical properties; surface strains
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Electron effective masses and mobilities in high‐purity 6H–SiC chemical vapor deposition layers

N. T. Son, O. Kordina, A. O. Konstantinov, W. M. Chen, E. Sörman, B. Monemar, and E. Janzén

Appl. Phys. Lett. 65, 3209 (1994); http://dx.doi.org/10.1063/1.112956 (3 pages) | Cited 43 times

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The first observation of cyclotron resonance in 6H‐SiC by optically detected cyclotron resonance (ODCR) spectroscopy at X‐band microwave frequency is reported. High purity undoped, n‐type 6H‐SiC layers grown by chemical vapor deposition (CVD), with residual doping concentrations in the 1014–1015 cm−3 range, were investigated. Effective mass values were determined as m∗⊥=(0.42±0.02)m0 and m∗∥=(2.0±0.2)m0. From the fit of the ODCR line shape, a remarkably high mobility at 6 K was deduced: μ⊥≊1.1×105 cm2/V s for electrons in the basal plane. The anisotropy of the effective mass and the carrier mobility is discussed in comparison with previously reported data. © 1994 American Institute of Physics.
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71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
73.50.Dn Low-field transport and mobility; piezoresistance
73.61.Le Other inorganic semiconductors

Relaxation of InGaAs layers grown on (111)B GaAs

A. Sacedón, F. Calle, A. L. Alvarez, E. Calleja, E. Muñoz, R. Beanland, and P. Goodhew

Appl. Phys. Lett. 65, 3212 (1994); http://dx.doi.org/10.1063/1.112415 (3 pages) | Cited 12 times

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The relaxation behavior of InGaAs layers grown by molecular beam epitaxy on (111)B GaAs is investigated and compared with simultaneously grown (100) reference samples. Surface morphology, defect microstructure, and optical quality of the layers during the relaxation process are studied by Nomarski interference contrast, transmission electron microscopy, low‐temperature photoluminescence, and Raman spectroscopy. These techniques reveal an inhomogeneous and anisotropic relaxation in (111) samples. In (111) samples, the increase of critical thickness and the slower relaxation dependence on thickness, as compared with the (100) reference samples, is discussed © 1994 American Institute of Physics.
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68.55.-a Thin film structure and morphology

ZnMgSeTe light emitting diodes

W. Faschinger, R. Krump, G. Brunthaler, S. Ferreira, and H. Sitter

Appl. Phys. Lett. 65, 3215 (1994); http://dx.doi.org/10.1063/1.112416 (3 pages) | Cited 11 times

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The MBE growth of light emitting diodes based on junctions between n‐ZnMgSe and p‐ZnMgSeTe is reported. For optimized compositions of the n‐ and p‐layer, doping levels as high as n=p=2×1018 cm−3 were obtained. The p contacts of these diodes are ohmic, and the voltage needed to achieve a given current density is comparable to that of the best ZnSe based p‐n junctions reported in the literature. The diodes show green electroluminescence up to room temperature. © 1994 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.66.Hf II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Effect of carrier charge imbalance on the threshold current in diode lasers with thin intrinsic quantum wells

G. A. Kosinovsky, M. Grupen, and K. Hess

Appl. Phys. Lett. 65, 3218 (1994); http://dx.doi.org/10.1063/1.112417 (3 pages) | Cited 8 times

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This study is based on the results of a two‐dimensional self‐consistent laser simulator MINILASE for the GaAs/AlGaAs system. It predicts that the electron/hole density ratio in thin quantum wells (QW’s) of laser diodes with intrinsic QW active regions (QW p‐i‐n lasers) can be significantly different from unity and depends on the doping density near the active region. These deviations from local charge neutrality can have significant effects on the laser threshold. © 1994 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.66.Fd III-V semiconductors

Deep‐oxide planar buried‐heterostructure AlGaAs–GaAs quantum well heterostructure laser diodes

M. R. Krames, E. I. Chen, and N. Holonyak

Appl. Phys. Lett. 65, 3221 (1994); http://dx.doi.org/10.1063/1.112418 (3 pages) | Cited 9 times

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Data are presented on deep‐oxide planar buried‐heterostructure AlGaAs–GaAs quantum well heterostructure laser diodes fabricated using a self‐aligned process that combines native oxide and impurity‐induced layer disordering (IILD) technologies. Silicon IILD intermixes the waveguide layers on either side of an active area stripe and allows ‘‘wet’’ oxidation to penetrate and create a low‐index (n∼1.7) deep‐oxide structure for electrical and optical confinement. Continuous‐wave (cw) threshold currents of ∼3.4 mA are measured for ∼3.5‐μm‐wide active regions (L∼250 μm), with maximum cw output powers greater than 29 mW/facet and external differential quantum efficiencies as high as 70% (300 K, uncoated facets). © 1994 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation

Electric field effects on the photoluminescence in modulation‐doped pseudomorphic AlGaAs/InGaAs/GaAs single quantum wells

G. M. Yang, K. S. Seo, and Byung‐Doo Choe

Appl. Phys. Lett. 65, 3224 (1994); http://dx.doi.org/10.1063/1.112419 (3 pages) | Cited 4 times

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Electric field effects on the photoluminescence spectra of modulation‐doped AlGaAs/InGaAs/GaAs single quantum wells grown by metalorganic chemical vapor deposition are studied. The electron density is continuously varied by the use of a Schottky gate. Parity forbidden transition is observed in the samples with a high electron density of more than 1×1012 cm−2. The luminescence line shape has strong dependence on the external bias. External field‐induced blue and red shifts of the optical transition at the n=1 conduction subband are found. The mechanism for this can be related to the quantum‐confined Stark shift, due to the competition between the built‐in field and the external field. No photoluminescence intensity enhancement is observed at the Fermi edge. © 1994 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Sensitivity of ion induced charge pulses to the electrical and crystallographic properties of 60° dislocations

M. B. H. Breese, P. J. C. King, and G. W. Grime

Appl. Phys. Lett. 65, 3227 (1994); http://dx.doi.org/10.1063/1.112420 (3 pages) | Cited 1 time

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This letter reports evidence that the size of MeV ion induced charge pulses measured from epitaxial Si0.875Ge0.125/Si depends on both the crystallographic and electrical properties of the 60° misfit dislocations present. The results are correlated with both backscattered and transmission ion channeling analysis. With the sample in nonchanneled alignment the measured ion induced charge pulses depend on the number of charge carriers which recombine at the dislocations. With the sample in channeled alignment the rotated (110) and (110) planes around the 60° dislocations affect the local rate of carrier generation and so alter the size of the measured ion induced charge pulses. © 1994 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

D (donor) X center behavior for holes implied from observation of metastable acceptor states

J. Han, M. D. Ringle, Y. Fan, R. L. Gunshor, and A. V. Nurmikko

Appl. Phys. Lett. 65, 3230 (1994); http://dx.doi.org/10.1063/1.112421 (3 pages) | Cited 19 times

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The observation of persistent photoconductivity in nitrogen‐doped p‐ZnMgSSe at low temperature is reported. The increase of conductivity after illumination appears due to a metastable population of holes which are in thermodynamic equilibrium with hydrogenic acceptors having reduced activation energy. The experimental evidence suggests the presence of a DX‐like [D (donor) X center] behavior for holes. © 1994 American Institute of Physics.
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71.55.Gs II-VI semiconductors
72.40.+w Photoconduction and photovoltaic effects
61.72.uj III-V and II-VI semiconductors

Low temperature synthesis of Ge nanocrystals in SiO2

Valentin Craciun, Ian W. Boyd, Alec H. Reader, and Dirk E. W. Vandenhoudt

Appl. Phys. Lett. 65, 3233 (1994); http://dx.doi.org/10.1063/1.112422 (3 pages) | Cited 18 times

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A novel and simple technique for the synthesis of Ge nanocrystals embedded in SiO2 is reported. The method is fully compatible with silicon microelectronic technology and relies solely upon low temperature (only 550 °C) ultraviolet oxidation of Si0.8Ge0.2 strained layers. This temperature is significantly lower than that usually used for the formation of Ge nanocrystals from SiGe oxides by H2 reduction. © 1994 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
61.46.-w Structure of nanoscale materials
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Low‐temperature Si(001) epitaxy using low‐energy (〈E 〉≂18 eV) Si atoms

N.‐E. Lee, G. A. Tomasch, and J. E. Greene

Appl. Phys. Lett. 65, 3236 (1994); http://dx.doi.org/10.1063/1.112423 (3 pages) | Cited 39 times

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The use of energetic (average energy ≂18 eV), rather than thermal (≂0.2 eV), Si beams during deposition at R=1 Å s−1 was found to increase the Si(001) epitaxial thickness te (100 Å–1.2 μm) by up to an order of magnitude over the growth temperature range Ts=80–300 °C. The overall increase in te is attributed primarily to a more effective filling of interisland trenches which form during growth in the low adatom mobility two‐dimensional multilayer mode and provide preferential sites for the nucleation of the terminal amorphous phase. In addition, the behavior of te(Ts) at constant R and te(R) at constant Ts is quite different than that reported for films grown by molecular‐beam epitaxy. A decrease in the slope of ln(te) versus −1/Ts at Ts<225 °C indicates an additional increase in the epitaxial thickness at very low growth temperatures while at constant Ts, 150 °C, te increases with decreasing R, reaches a maximum, and then decreases. These latter effects are explained in terms of changes in average island sizes giving rise to corresponding changes in interlayer mass transport. © 1994 American Institute of Physics.
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68.55.-a Thin film structure and morphology

Improved crystalline quality of AlAsxSb1−x grown on InAs by modulated molecular‐beam epitaxy

Yong‐Hang Zhang and David H. Chow

Appl. Phys. Lett. 65, 3239 (1994); http://dx.doi.org/10.1063/1.112424 (3 pages) | Cited 9 times

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This letter reports a dramatic improvement in crystalline quality of AlAs0.16Sb0.84 ordered alloys compared with random ones grown by modulated molecular‐beam epitaxy (MMBE) on InAs substrates. The average As/Sb ratio in these ordered alloys is accurately controlled by the modulation of As2 and Sb2 beams. The surface morphology of the epilayers is mirrorlike to the naked eye and appears texture‐ and cluster‐free under an electron scanning microscope. X‐ray diffraction measurements reveal that the lattice‐matched conditions for AlAsxSb1−x epilayers to InAs can be easily achieved by simply changing the As‐shutter dutycycle. Distinct satellite peaks corresponding to the ordered structure with a period of about 11 Å are also clearly observed. Strong photoluminescence (PL) is observed from GaAs0.08Sb0.92/AlAs0.16Sb0.84 single quantum well structures up to room temperature under a very low photoexcitation (5 W/cm2). At 5 K the PL linewidth is 4.5 meV. © 1994 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
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