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30 Jan 1995

Volume 66, Issue 5, pp. 535-648

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High quantum efficiency dual wavelength resonant‐cavity photodetector

A. Srinivasan, S. Murtaza, J. C. Campbell, and B. G. Streetman

Appl. Phys. Lett. 66, 535 (1995); http://dx.doi.org/10.1063/1.114004 (3 pages) | Cited 5 times

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A new dual‐wavelength, resonant‐cavity photodiode is described. It has previously been shown that the resonant‐cavity structure can achieve high quantum efficiencies in a relatively narrow spectral region with thin absorbing regions. In this letter, a dual wavelength mirror is incorporated into the cavity to achieve operation in two wavelength regions. Peak external quantum efficiencies greater than 50% were demonstrated at 730 and 910 nm. © 1995 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
42.79.Pw Imaging detectors and sensors
78.66.Fd III-V semiconductors

Vertical transition quantum cascade laser with Bragg confined excited state

Jérôme Faist, Federico Capasso, Carlo Sirtori, Deborah L. Sivco, Albert L. Hutchinson, and Alfred Y. Cho

Appl. Phys. Lett. 66, 538 (1995); http://dx.doi.org/10.1063/1.114005 (3 pages) | Cited 105 times

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A new midinfrared (λ∼4.5 μm) intersubband quantum cascade laser based on a vertical transition is reported. A superlattice graded gap region was incorporated in the design to provide strong electron confinement in the upper state using a Bragg reflector. Pulsed operation at 100 K is reported with a threshold current density of Jth=3 kA/cm2 and a measured slope efficiency of 300 mW/A. © 1995 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation

Light propagation, optical modulation, and beam steering in waveguides with quantum well voltage tunable claddings

Alex Harwit, R. Fernandez, D. K. Kinell, and W. D. Eades

Appl. Phys. Lett. 66, 541 (1995); http://dx.doi.org/10.1063/1.114006 (3 pages) | Cited 2 times

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We present results on devices fabricated in a waveguide system utilizing a voltage tunable quantum well cladding layer. A (GaAs/AlGaAs) beam steering device produced an angular shift of 2.4° under an applied voltage of 20 V. It is shown numerically that electro‐optic modulators fabricated in such a material configuration can have simultaneously improved contrast ratios and insertion losses if the ratio of light propagating in the cladding and in the core regions can be controlled. A proof of concept device is demonstrated in which an electric field is used to change the distribution of light propagating in the waveguide. © 1995 American Institute of Physics.
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78.66.Fd III-V semiconductors
42.79.Gn Optical waveguides and couplers
42.79.Hp Optical processors, correlators, and modulators

Negative submillimeter absorption in tunnel‐coupled quantum wells under resonant infrared excitation

F. T. Vasko and Yu. N. Soldatenko

Appl. Phys. Lett. 66, 544 (1995); http://dx.doi.org/10.1063/1.114007 (3 pages) | Cited 5 times

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We have studied the redistribution of the electrons between the tunnel‐coupled ground levels in double quantum wells (DQWs), caused by the resonant infrared (IR) excitation on the next level and relaxation of the photoexcited electrons due to spontaneous emission of the optical phonons. The condition for the inversion of the electron populations in the tunnel‐coupled pair of ground states is presented as a function of the DQWs parameters. Negative absorption coefficient of the submillimeter radiation under intensive (2–4 kW/cm2) IR pumping and commonly realized parameters of DQWs is of order 20–50 cm−1. © 1995 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.66.-w Optical properties of specific thin films
78.30.-j Infrared and Raman spectra

Blue light emission from a laser diode pumped ring resonator with an organic second‐harmonic generation crystal of 8‐(4′‐acetylphenyl)‐1,4‐dioxa‐8‐azaspirol[4.5]decane

M. Sagawa, H. Kagawa, A. Kakuta, M. Kaji, M. Saeki, and Y. Namba

Appl. Phys. Lett. 66, 547 (1995); http://dx.doi.org/10.1063/1.114008 (3 pages) | Cited 10 times

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A laser diode pumped ring resonator was built with a new organic second‐order nonlinear optical crystal, 8‐(4′‐acetylphenyl)‐1,4‐dioxa‐8‐azaspiro[4.5] decane. Ultraprecision diamond polishing was used for the crystal and optically flat surfaces and roughnesses of less than λ/10 were achieved. The surfaces were dip coated with a perfluorinated polymer thin film to suppress surface reflection loss. Under resonant conditions, fundamental power was enhanced and a blue second‐harmonic emission with wavelength of 405.5 nm was observed. © 1995 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Theoretical analysis of ultrafast pump‐probe experiments in semiconductor amplifiers

A. Girndt, A. Knorr, M. Hofmann, and S. W. Koch

Appl. Phys. Lett. 66, 550 (1995); http://dx.doi.org/10.1063/1.114009 (3 pages) | Cited 8 times

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Pump‐probe experiments in semiconductor amplifiers are analyzed theoretically. On the basis of Maxwell–Semiconductor–Bloch equations it is shown that the probe signal exhibits dominant oscillatory interference‐like structures. These structures are superimposed on the pump and probe intensity dependent features. The calculations are qualitatively similar to experimental results. © 1995 American Institute of Physics.
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78.47.-p Spectroscopy of solid state dynamics

Demonstration of a two stage backward‐wave oscillator and free‐electron laser

Zheng Liang, Ziqiang Yang, Tianquan Den, and Shengang Liu

Appl. Phys. Lett. 66, 553 (1995); http://dx.doi.org/10.1063/1.114010 (3 pages)

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The experimental study of a two‐stage scheme in which the same intense relativistic electron beam (0.6 MV, 3 kA, 70 ns) first produces powerful radiation (100 MW) at 3.0 cm and then the radiation is used as a pump wave for a free‐electron laser interaction at 3.0 mm is described. The results of the experiment and nonlinear theory are discussed. © 1995 American Institute of Physics.
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41.60.Cr Free-electron lasers
52.59.Px Hard X-ray sources

Phased array of high‐power, coherent, monolithic flared amplifier master oscillator power amplifiers

J. S. Osinski, D. Mehuys, D. F. Welch, R. G. Waarts, J. S. Major, K. M. Dzurko, and R. J. Lang

Appl. Phys. Lett. 66, 556 (1995); http://dx.doi.org/10.1063/1.114011 (3 pages) | Cited 5 times

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A monolithically integrated array of InGaAs/AlGaAs flared amplifiers driven by a single DBR laser through a power splitter network and individually addressed phase modulators is described. Phase adjustment of ≳2π per element by free‐carrier effects is verified by monitoring the interference pattern of all four emitters, and typically requires <15 mA of current to obtain a 2π phase shift. Phase matching is achieved among all four diffraction‐limited emitters at a pulsed output power of ≳5 W, and, combined with the proper external lensing, could therefore result in an ultranarrow, single‐lobed far‐field pattern whose width is determined by the extended aperture of the array. © 1995 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation

Plasma‐heating induced intensity‐dependent gain in semiconductor lasers

C. Z. Ning and J. V. Moloney

Appl. Phys. Lett. 66, 559 (1995); http://dx.doi.org/10.1063/1.114012 (3 pages) | Cited 7 times

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Starting from a set of equations derived from a microscope theory we show that the familiar nonlinear gain of the form a/(1+I/Is) introduced in semiconductor laser rate equations phenomenologically should be replaced by a more general form of a/(1+I/Is)b. The new scaling exponent b depends on the relaxation constant γT that describes the rate of heat dissipation from plasma to the lattice due to carrier‐phonon scattering. © 1995 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Cathodoluminescence study of erbium and oxygen coimplanted gallium nitride thin films on sapphire substrates

C. H. Qiu, M. W. Leksono, J. I. Pankove, J. T. Torvik, R. J. Feuerstein, and F. Namavar

Appl. Phys. Lett. 66, 562 (1995); http://dx.doi.org/10.1063/1.114013 (3 pages) | Cited 42 times

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The cathodoluminescence (CL) of erbium and oxygen coimplanted GaN (GaN:Er:O) and sapphire (sapphire:Er:O) was studied as a function of temperature. Following annealing, the 1.54 μm intra‐4f‐shell emission line was observed in the temperature range of 6–380 K. As the temperature increased from 6 K to room temperature, the integrated intensity of the infrared peak decreased by less than 5% for GaN:Er:O, while it decreased by 18% for sapphire:Er:O. The observation of minimal thermal quenching by CL suggests that Er and O doped GaN is a promising material for electrically pumped room‐temperature optical devices emitting at 1.54 μm. © 1995 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
71.55.Eq III-V semiconductors
78.66.Fd III-V semiconductors

Surface sources of piezoelectric transduction

Yuan Liu

Appl. Phys. Lett. 66, 565 (1995); http://dx.doi.org/10.1063/1.114014 (3 pages)

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Recently, a complete formulation of the transient surface excitation problem for piezoelectric materials has suggested the existence of a type of electrical sources on the surface not traditionally considered in piezoelectric transduction. This letter shows that these additional sources correspond to electric current dipoles. It is shown that the wave forms, or the frequency dependence, of waves generated by these sources are different from those generated by traditionally studied sources such as mechanical stresses and electric currents. These characteristics can be used to identify the contribution of such sources. Schottky and p‐n junctions on the surface of a semiconductive material are suggested as the experimental implementation of the new sources. In addition to piezoelectric transduction, current dipoles can also be used to generate electromagnetic waves in a nonpiezoelectric medium. © 1995 American Institute of Physics.  
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77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
43.38.Ar Transducing principles, materials, and structures: general
43.38.Fx Piezoelectric and ferroelectric transducers

Trap‐limited interstitial diffusion and enhanced boron clustering in silicon

P. A. Stolk, H.‐J. Gossmann, D. J. Eaglesham, D. C. Jacobson, J. M. Poate, and H. S. Luftman

Appl. Phys. Lett. 66, 568 (1995); http://dx.doi.org/10.1063/1.114015 (3 pages) | Cited 72 times

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Boron doped superlattices have been used to detect the diffusion of self‐interstitials in Si. Interstitials were generated in the near‐surface region by 40 keV Si implantation followed by diffusion at 670–790 °C. The interstitial diffusion profile at 670 °C is stationary for t≤1 h, demonstrating that the penetration depth of interstitials is limited by trapping. The concentration of traps is estimated to be ∼1017/cm3. For sufficiently long annealing times, interstitials diffuse beyond the trapping length with an effective trap‐limited diffusivity ranging from ∼6×10−15 cm2/s at 670 °C to ∼1×10−12 cm2/s at 790 °C. The high interstitial supersaturation adjacent to the implant damage drives substitutional B into metastable clusters at concentrations below the B solid solubility limit. © 1995 American Institute of Physics.
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66.30.-h Diffusion in solids
61.72.uf Ge and Si
61.72.J- Point defects and defect clusters

Phase transitions in the Pb(In1/2Nb1/2)O3–PbZrO3 system

Naohiko Yasuda and Takuya Mizuno

Appl. Phys. Lett. 66, 571 (1995); http://dx.doi.org/10.1063/1.114016 (3 pages) | Cited 8 times

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Phase transitions and dielectric properties of (1−x)Pb(In1/2Nb1/2)O3(PIN)‐xPbZrO3(PZ) solid solution system have been examined as a function of the concentration x. Two morphotropic phase boundaries were identified: (1) pseudocubic to rhombohedral phase boundary at x=0.35 and (2) rhombohedral to orthorhombic at x=0.8. For x<0.35, a diffuse phase transition was observed. For 0.35<x<0.8, the relative permittivity ϵ′r showed a sharp peak at Tc. In this regime, the phase below Tc was confirmed to be ferroelectric by observation square P‐E hysteresis loops. For x≳0.8, a steplike dielectric anomaly appeared at Tt (below Tc) as well as the sharp peak in the permittivity. The phase below Tt was confirmed to be antiferroelectric by the observation of double P‐E hysteresis loops. The maximum permittivity of 15 000 (at 100 kHz) was observed at x=0.35 © 1995 American Institute of Physics.
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77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
77.80.-e Ferroelectricity and antiferroelectricity

Reduced effective misfit in laterally limited structures such as epitaxial islands

S. Christiansen, M. Albrecht, H. P. Strunk, P. O. Hansson, and E. Bauser

Appl. Phys. Lett. 66, 574 (1995); http://dx.doi.org/10.1063/1.114017 (3 pages) | Cited 50 times

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Numerical finite element calculations have been reported to determine a correction function Φ that describes the reduction of the misfit that occurs when laterally limited structures such as faceted islands or mesa structures are grown on a substrate. The reduction of the average strain energy density is calculated in these three‐dimensional islands and compared to the constant strain energy density in a continuous layer. Ratios Φ are obtained from the calculation of different island geometries, i.e., different facet angles γ and different aspect ratios island width l to island height h. These discrete values are fitted by a function which can easily be applied to the full range of aspect ratios (l/h≳0) and facet angles (0°<γ<90°). Faceted Ge(Si) islands on Si(001) substrate, grown from the solution in the Stranski–Krastanov growth mode, serve as an example for the calculation. Experimental and theoretical values for the critical thickness of these islands agree well. This result demonstrates the drastic influence of islanding on misfit strain distribution in island and substrate as well and, consequently, on the strong increase of the critical thickness as determined by the mechanical equilibrium theory of Matthews and Blakeslee. © 1995 American Institute of Physics.
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68.55.-a Thin film structure and morphology

Study of the effect of boron doping on the aging of micromachined silicon cantilevers

Andrew Pember, Jim Smith, and Henri Kemhadjian

Appl. Phys. Lett. 66, 577 (1995); http://dx.doi.org/10.1063/1.114018 (3 pages) | Cited 4 times

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Micromachined silicon cantilevers have been prepared using anisotropic etching in conjunction with boron doping. They were driven into resonant vibration for periods of over 2000 h and their natural frequencies and quality factors were recorded as a function of aging time. It has been found that aging has occurred in all of the samples tested and this was manifest as an increase in the quality factor and a small decrease in resonant frequency, with both values eventually stabilizing. The magnitude of this effect was found to increase with increasing levels of boron doping within the structures. The mechanism of aging is not clear but may be linked to dislocation damage and activity of interstitial boron with the crystals. © 1995 American Institute of Physics.
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62.30.+d Mechanical and elastic waves; vibrations
62.20.-x Mechanical properties of solids
81.40.Lm Deformation, plasticity, and creep

Effects of strain on boron diffusion in Si and Si1−xGex

P. Kuo, J. L. Hoyt, J. F. Gibbons, J. E. Turner, and D. Lefforge

Appl. Phys. Lett. 66, 580 (1995); http://dx.doi.org/10.1063/1.114019 (3 pages) | Cited 76 times

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Boron diffusion in in situ doped Si1−xGex and Si, subjected to inert‐ambient furnace annealing at 800 °C, was investigated. For Si1−xGex, the effect of biaxial compressive and tensile strain on boron diffusion was studied using Si1−xGex layers with a constant Ge content (x≊0.10 and x≊0.20) grown epitaxially on various relaxed Si1−yGey (0≤y≤0.20) substrates. Boron diffusion is primarily a function of Ge content, x in the Si1−xGex layers, and does not show a strong dependence on macroscopic biaxial strain. For Si, the effect of biaxial tension was investigated using relaxed Si1−yGey layers as substrate templates for epitaxial Si layers. As in Si1−xGex, boron diffusion in Si does not depend strongly on biaxial strain. © 1995 American Institute of Physics.
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66.30.J- Diffusion of impurities
61.72.uf Ge and Si
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Heteroepitaxial growth of smooth and continuous diamond thin films on silicon substrates via high quality silicon carbide buffer layers

H. Kawarada, T. Suesada, and H. Nagasawa

Appl. Phys. Lett. 66, 583 (1995); http://dx.doi.org/10.1063/1.114020 (3 pages) | Cited 63 times

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Smooth and continuous diamond films have been heteroepitaxially grown on β‐type silicon carbide (β‐SiC) (001) surfaces. The smooth films can be obtained in the thickness of less than 6 μm which is the smallest in heteroepitaxial diamonds. The epitaxial growth is composed of three steps; (i) Bias enhanced nucleation on β‐SiC (001) grown on silicon (001), (ii) 〈001〉 fast growth mode for the selection of epitaxially oriented particles, and (iii) 〈111〉 fast growth mode for the smoothing of (001) surface. High quality silicon carbide (001) surface is effective for oriented diamond nucleation. The winnowing process of oriented particles and the surface adjustment are due to the high surface energy of diamond. © 1995 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

Photoluminescence of modulation‐doped ordered–disordered GaInP2 homojunctions: Intrinsic versus extrinsic emissions

F. A. J. M. Driessen, P. R. Hageman, S. M. Olsthoorn, and L. J. Giling

Appl. Phys. Lett. 66, 586 (1995); http://dx.doi.org/10.1063/1.114021 (3 pages) | Cited 1 time

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Photoluminescence (PL) measurements are reported on modulation‐doped ordered‐GaInP2/ disordered‐GaInP2 homojunctions. These junctions exhibit extremely high carrier densities of the two‐dimensional (2D) electron gas. A luminescence peak that involves recombination of these intrinsic 2D electrons and photoexcited holes shows a very large redshift as a result of the spatially separated carriers. However, no inverted S shaped behavior of PL energy is observed for this signal upon increasing temperature. This result affirms that the inverted S PL behavior of bulk ordered GaInP2 has an extrinsic nature. © 1995 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Enhanced hot‐carrier spontaneous and stimulated recombination in a photopumped vertical cavity AlxGa1−xAs–GaAs quantum well heterostructure with multiple top and bottom native oxide mirrors

T. A. Richard, S. A. Maranowski, N. Holonyak, E. I. Chen, M. J. Ries, J. G. Neff, P. A. Grudowski, and R. D. Dupuis

Appl. Phys. Lett. 66, 589 (1995); http://dx.doi.org/10.1063/1.114022 (3 pages) | Cited 9 times

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Data (300 and 77 K) are presented on the photopumped laser operation of AlxGa1−xAs–GaAs vertical cavity quantum well heterostructure crystals that exhibit enhanced hot‐carrier recombination. The mirrors defining the vertical cavity are formed by selective lateral oxidation (H2O+N2, 425 °C, 30 min) of quadruple AlAs layers separated by lower composition AlxGa1−xAs ‘‘stop’’ layers in order to create upper and lower high‐index‐step oxide‐semiconductor distributed Bragg reflector mirrors. The Q of the compact vertical‐cavity (a microcavity) enhances the spontaneous and stimulated recombination of hot carriers, making possible single mode laser operation at an energy corresponding to the second state of the quantum well. The laser operation can be shifted to the first state by cooling to 77 K and shifting the energy gap towards the vertical cavity resonance. © 1995 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.45.+h Stimulated emission

Advantage of rapid thermal annealing over furnace annealing for P‐implanted metastable Si/Ge0.12Si0.88

D. Y. C. Lie, J. H. Song, M.‐A. Nicolet, and N. D. Theodore

Appl. Phys. Lett. 66, 592 (1995); http://dx.doi.org/10.1063/1.114023 (3 pages) | Cited 13 times

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Metastable pseudomorphic Ge0.12Si0.88 films were grown by molecular beam epitaxy on Si(100) substrates and then implanted with 100 keV 31P at room temperature for a dose of 5×1013/cm2. Samples were subsequently annealed by rapid thermal annealing (RTA) in nitrogen and by steady‐state furnace annealing in vacuum. Both damage and strain introduced by implantation can be completely removed, within instrumental sensitivity, by RTA at 700 °C for 10–40 s. Vacuum annealing for 30 min at 500–550 °C removes most of the damage and strain induced by the implantation but the activation of the P is poor. At 700 °C, the activation is nearly 100%, but the crystallinity worsens and the pseudomorphic strain begins to relax. We conclude that for a lightly implanted metastable and pseudomorphic GeSi epilayer on Si, steady‐state vacuum annealing cannot achieve good dopant activation without introducing significant strain relaxation to the heterostructure, while RTA can. © 1995 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.uf Ge and Si
61.80.Jh Ion radiation effects
61.72.Cc Kinetics of defect formation and annealing

High deposition rate amorphous silicon‐based multijunction solar cell

S. Guha, X. Xu, J. Yang, and A. Banerjee

Appl. Phys. Lett. 66, 595 (1995); http://dx.doi.org/10.1063/1.114024 (3 pages) | Cited 14 times

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We have investigated and optimized the deposition conditions for growth of amorphous silicon (a‐Si:H) and silicon‐germanium (a‐SiGe:H) alloys at high rates using microwave glow discharge. The optimum substrate temperature is found to be higher and deposition pressure lower than the case for materials deposited at low rates using radio‐frequency glow discharge. Using the optimized conditions, we report an active‐area efficiency of 11.44% for a double‐junction, dual‐gap a‐Si:H alloy solar cell in which the bottom cell incorporates a‐SiGe:H alloy deposited at 100 Å/s. © 1995 American Institute of Physics.
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84.60.Jt Photoelectric conversion
78.66.Jg Amorphous semiconductors; glasses
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Substrate bias effect on the capture kinetics of random telegraph signals in submicron p‐channel silicon metal–oxide–semiconductor transistors

E. Simoen and C. Claeys

Appl. Phys. Lett. 66, 598 (1995); http://dx.doi.org/10.1063/1.114025 (3 pages) | Cited 1 time

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This letter investigates the effect of the substrate bias on the capture kinetics of random telegraph signals in submicron silicon p‐channel metal–oxide–semiconductor transistors. A strong dependence of the capture time constant τc on the transverse electric field is observed. As a result, τc∼exp(−Ap) is observed experimentally, which is much stronger than the 1/p dependence predicted by simple Shockley–Read–Hall theory, whereby p is the surface density of free holes. The observations are explained tentatively by considering a field‐dependent hole capture cross section. The latter may result from quantization effects induced by the transverse field in the two‐dimensional inversion layer. © 1995 American Institute of Physics.
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72.70.+m Noise processes and phenomena
73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.30.Tv Field effect devices

Al diffusion into GaAs from monatomic AlAs layers investigated by localized vibrational modes

Haruhiko Ono, Nobuyuki Ikarashi, and Toshio Baba

Appl. Phys. Lett. 66, 601 (1995); http://dx.doi.org/10.1063/1.114026 (3 pages) | Cited 1 time

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Using infrared absorption spectroscopy, we investigate the thermal diffusion behavior of Al atoms from monatomic Al layers embedded in a GaAs epitaxial film. After thermal annealing, the absorption peak of the two‐dimensionally localized vibrational modes at 358 cm−1 due to Al layers decreases, while the peak at 362 cm−1 due to isolated Al atoms increases. The 362 cm−1 peak height is compared with the fraction of isolated Al atoms calculated, assuming the second nearest neighbor hopping diffusion from a monatomic Al layer into GaAs matrix. We thus determine the diffusion coefficient of Al atoms in GaAs to be 2×10−19 cm2/s at 700 °C. The present study offers a simple and reliable method to investigate the impurity diffusion in crystals. © 1995 American Institute of Physics.
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68.35.Fx Diffusion; interface formation
66.30.J- Diffusion of impurities
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Surface morphology of metalorganic vapor phase epitaxy grown strained‐layer InxGa1−xAs on GaAs observed by atomic force microscopy

C. C. Hsu, J. B. Xu, I. H. Wilson, and S. M. Wang

Appl. Phys. Lett. 66, 604 (1995); http://dx.doi.org/10.1063/1.114027 (3 pages) | Cited 6 times

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We have studied the surface morphology and growth mechanism of metalorganic vapor phase epitaxy grown strained‐layer InxGa1−xAs (x=0.2 or 0.5) on GaAs with atomic force microscopy. Morphological instability of monolayer steps was observed on a 10 nm thick strained‐layer In0.2Ga0.8As. Three‐dimensional (3D) growth was observed for x=0.5 when grown at 650 °C. By lowering the growth temperature to 600 °C, the growth mode is 2‐D for 5 nm films (x=0.5). Monolayer steps and 2D islands can be seen. Increasing the layer thickness to 7.5 nm at 600 °C caused the growth of 3D islands and the generation of misfit dislocations. © 1995 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

Simultaneous blue‐ and red‐shift of light‐hole and heavy‐hole band in a novel variable‐strain quantum well heterostructure

Weimin Zhou, H. Shen, J. Pamulapati, P. Cooke, and M. Dutta

Appl. Phys. Lett. 66, 607 (1995); http://dx.doi.org/10.1063/1.114028 (3 pages) | Cited 6 times

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We have designed and studied a new type of strained semiconductor quantum well structure, variable‐strain quantum well. The strain within the quantum well is graded from compressive to tensile in order to obtain mutually opposing slopes for the heavy‐ and light‐hole band edges, causing the heavy and light holes to experience opposite fields created by the same strain. A unique bias controlled crossover with a simultaneous red and blue quantum confined Stark shift for the heavy‐ and light‐hole transitions, respectively, has been observed by electroreflectance spectra. This results in a bias controlled change of the polarization properties and the transition energies suitable for polarization controllable photonic devices. © 1995 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.66.Fd III-V semiconductors
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
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