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25 Oct 1993

Volume 63, Issue 17, pp. 2309-2443

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Maskless writing of submicrometer gratings in fused silica by focused ion beam implantation and differential wet etching

J. Albert, K. O. Hill, B. Malo, D. C. Johnson, F. Bilodeau, I. M. Templeton, and J. L. Brebner

Appl. Phys. Lett. 63, 2309 (1993); http://dx.doi.org/10.1063/1.110509 (3 pages) | Cited 16 times

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Surface relief gratings with submicrometer periods have been fabricated in silica by ion implantation with a focused ion beam, followed by etching in diluted hydrofluoric acid. Implanted silica etches three times faster than unimplanted silica and groove depths of the order of 300 nm have been achieved. The method does not require photolithography or masking layers, allows arbitrary patterns to be defined, and may be used to fabricate diffractive optical elements or grating filters in optical waveguides.
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81.05.Kf Glasses (including metallic glasses)
81.65.-b Surface treatments
42.70.Ce Glasses, quartz
42.79.Dj Gratings

Strained layer GaAs1−yPy‐AlGaAs and InxGa1−xAs‐AlGaAs quantum well diode lasers

C. J. van der Poel, H. P. M. M. Ambrosius, R. W. M. Linders, R. M. L. Peeters, G. A. Acket, and M. P. C. M. Krijn

Appl. Phys. Lett. 63, 2312 (1993); http://dx.doi.org/10.1063/1.110510 (3 pages) | Cited 12 times

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Separate confinement strained layer single quantum well diode lasers on GaAs substrates have been fabricated by low‐pressure organometallic vapor phase epitaxy. Laser diode structures with a 90 Å quantum well under compressive strain, composed of InxGa1−xAs with x=0.00–0.17, as well as tensile strain, composed of GaAs1−yPy with y=0.00–0.29, have been studied. The emission wavelength ranges from λ=746 nm for y=0.29 up to λ=962 nm for x=0.17. The strain dependence of the threshold current for broad area devices is studied both experimentally and theoretically as a function of temperature. Regions of optimal laser performance, one for compressive and one for tensile strain, are identified.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation

Low‐threshold buried‐ridge II‐VI laser diodes

M. A. Haase, P. F. Baude, M. S. Hagedorn, J. Qiu, J. M. DePuydt, H. Cheng, S. Guha, G. E. Höfler, and B. J. Wu

Appl. Phys. Lett. 63, 2315 (1993); http://dx.doi.org/10.1063/1.110511 (3 pages) | Cited 36 times

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Blue‐green (λ=511 nm) separate confinement laser structures based on lattice‐matched MgZnSSe‐ZnSSe‐CdZnSe have been grown by molecular beam epitaxy. Wide stripe gain‐guided devices have been fabricated from several such wafers. These devices exhibit room‐temperature pulsed threshold current densities as low as 630 A/cm2 and threshold voltages less than 9 V. Using a novel self‐aligned process that results in a planar surface, buried‐ridge laser diodes have also been fabricated. These devices have demonstrated room‐temperature threshold currents as low as 2.5 mA, which is more than a factor of 50 lower than that of any previously reported II‐VI laser diode. Room‐temperature operation at duty factors up to 50% has been demonstrated. The far‐field patterns from these devices indicate single lateral mode operation, suitable for diffraction‐limited applications, such as optical data storage.  
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation

Single‐wavelength all‐optical phase modulation in a GaAs/AlAs hetero‐nipi waveguide: Towards an optical transistor

G. W. Yoffe, J. Brübach, F. Karouta, and J. H. Wolter

Appl. Phys. Lett. 63, 2318 (1993); http://dx.doi.org/10.1063/1.110512 (3 pages) | Cited 2 times

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We propose and demonstrate a single‐wavelength all‐optical transistor‐like device, exploiting the polarization‐dependent absorption coefficient in quantum wells. The device is a GaAs/AlAs multiple‐quantum‐well hetero‐nipi waveguide structure. A transverse‐electric (TE)‐polarized control beam is absorbed, changing the refractive index through carrier‐induced effects. A transverse‐magnetic‐polarized probe beam at the same wavelength, to which the material is transparent, undergoes a phase shift, which can be converted to amplitude modulation if required. The probe can be more powerful than the control beam, so the device can exhibit gain. We obtained a 180° phase shift in the probe beam with 4.2 mW of absorbed control light. The effect was greater with an applied dc bias. A 180° phase shift was obtained at 831 nm with 2.8 mW absorbed TE light and 0.5 V bias.
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42.79.Hp Optical processors, correlators, and modulators
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
78.66.Fd III-V semiconductors

Strained quaternary quantum well lasers for high temperature operation

H. Temkin, D. Coblentz, R. A. Logan, J. M. Vandenberg, R. D. Yadvish, and A. M. Sergent

Appl. Phys. Lett. 63, 2321 (1993); http://dx.doi.org/10.1063/1.110513 (3 pages) | Cited 12 times

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We describe compressively strained separate confinement heterostructure 1.3 μm quantum well lasers optimized for high temperature operation. The active layer consists of ten GaInAsP wells, each 40–80 Å thick, grown under compressive lattice mismatch strain of Δa/a≤0.75%. Within the constraints of the well composition and thickness imposed on the active region, strain is necessary for efficient laser operation. Best results are obtained for Δa/a∼0.2%–0.3% with the laser threshold as low as 5 mA and slope efficiency of 42 mW/mA. In the temperature range of 25–85 °C a slope efficiency change as small as 30% was achieved. Power output of at least 20 mW can be maintained up to 100 °C at a current drive below 150 mA.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation

Second harmonic generation from SimGen superlattices

D. J. Bottomley, G. Lüpke, M. L. Ledgerwood, X. Q. Zhou, and H. M. van Driel

Appl. Phys. Lett. 63, 2324 (1993); http://dx.doi.org/10.1063/1.110514 (3 pages) | Cited 16 times

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We report the observation of optical second harmonic generation (SHG) from SimGen short‐period superlattices grown on different substrates. For a 775 nm fundamental beam, the SHG signals from odd‐odd, even‐even, and even‐odd specimens are comparable, apart from substrate‐dependent strain enhancement. It is concluded that the lack of a large bulk dipole‐allowed signal in odd‐odd superlattices predicted by Ghahramani, Moss, and Sipe [Phys. Rev. Lett. 64, 2815 (1990)] is due to the inevitable presence of monatomic steps on the substrate which lead to antiphase domains; a possible circumvention of this limitation is outlined based on the use of a single domain vicinal Si(001) substrate.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.66.Li Other semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

High power continuous wave blue light generation in KNbO3 using semiconductor amplifier seeded by a laser diode

L. Goldberg, L. E. Busse, and D. Mehuys

Appl. Phys. Lett. 63, 2327 (1993); http://dx.doi.org/10.1063/1.110515 (3 pages) | Cited 17 times

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Diffraction limited emission of a GaAlAs tapered amplifier seeded by a laser diode is frequency doubled in a 12.4‐mm‐long KNbO3 crystal to generate 62 mW of 429 nm continuous wave emission, corresponding to a conversion efficiency of 1.1%/W cm. Reductions in the conversion efficiency due to nonuniform temperature distribution caused by blue‐enhanced infrared absorption were characterized.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Role of excitation frequency in a low‐pressure, inductively coupled radio‐frequency, magnetized plasma

Chunshi Cui and R. W. Boswell

Appl. Phys. Lett. 63, 2330 (1993); http://dx.doi.org/10.1063/1.110516 (3 pages) | Cited 1 time

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We have experimentally studied the role of the excitation frequency frf in a low‐pressure, inductively coupled radio‐frequency (rf), magnetized plasma. Planar Langmuir probe measurements of the electron energy distribution function and the plasma density ne clearly demonstrate a sudden change in the nature of plasma‐rf coupling as frf approaches the electron cyclotron frequency fce from below or above. The observed mode change is qualitatively explained by different wave coupling mechanism for frf<fce and frf≳fce. These observations could have important applications for plasma processing.
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52.80.Pi High-frequency and RF discharges
52.50.Gj Plasma heating by particle beams
52.70.Ds Electric and magnetic measurements

Emission spectra analyses of a new vacuum ultraviolet source

M. L. Sentis, F. Chazaud, Ph. C. Delaporte, and W. I. Marine

Appl. Phys. Lett. 63, 2333 (1993); http://dx.doi.org/10.1063/1.110517 (3 pages) | Cited 2 times

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Spectroscopic study of a formed‐ferrite plasma source has been carried out in the 115–210 nm spectral region. Emission spectra are dominated either by atomic lines superimposed on continuum emission depending on the surrounding gas. Atomic lines are related to the emission from electronic transitions of singly or multi‐ionized atomic species of the ferrite. The electronic density of such a vacuum ultraviolet source is estimated to 4×1018 cm−3 based on Stark broadening effect.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.80.-s Electric discharges
42.72.Bj Visible and ultraviolet sources

Etching yields of SiO2 by low energy CFx+ and F+ ions

Teruo Shibano, Nobuo Fujiwara, Makoto Hirayama, Hitoshi Nagata, and Kiyoshi Demizu

Appl. Phys. Lett. 63, 2336 (1993); http://dx.doi.org/10.1063/1.110518 (3 pages) | Cited 26 times

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Etching yields of SiO2 by mass‐separated F+, CF+, CF2+, CF3+, and Ar+ ions have been measured at low ion energies ranging from 80 to 350 eV. CF3+ and CF2+ ions have higher etching yields than CF+ and F+ ions. At low ion energies, SiO2 cannot be etched and some film deposition is observed on the SiO2 surface. For example, in the case of CF+ ions, SiO2 can be etched at ion energies above 200 eV. This film deposition is caused by reactions of CFx+ ions at the SiO2 surface, and neutrals coming from the ion source also have some effect on this deposition.
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81.65.-b Surface treatments
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Absorption spectroscopic measurement of atomic density in laser‐induced vapor plume

T. P. Duffey, T. G. McNeela, J. Mazumder, and A. L. Schawlow

Appl. Phys. Lett. 63, 2339 (1993); http://dx.doi.org/10.1063/1.110519 (3 pages) | Cited 4 times

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Laser absorption spectroscopy employing a tunable continuous wave dye laser has been used to measure the density of atomic niobium vapor in a laser ablation plume near the target surface. Population densities for one atomic level were measured to be ∼2×1015 cm−3 near the center of the plume.
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81.15.Fg Pulsed laser ablation deposition
79.20.Ds Laser-beam impact phenomena
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

A highly processable metallic glass: Zr41.2Ti13.8Cu12.5Ni10.0Be22.5

A. Peker and W. L. Johnson

Appl. Phys. Lett. 63, 2342 (1993); http://dx.doi.org/10.1063/1.110520 (3 pages) | Cited 1248 times

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We report on the properties of one example of a new family of metallic alloys which exhibit excellent glass forming ability. The critical cooling rate to retain the glassy phase is of the order of 10 K/s or less. Large samples in the form of rods ranging up to 14 mm in diameter have been prepared by casting in silica containers. The undercooled liquid alloy has been studied over a wide range of temperatures between the glass transition temperature and the thermodynamic melting point of the equilibrium crystalline alloy using scanning calorimetry. Crystallization of the material has been studied. Some characteristic properties of the new material are presented. The origins of exceptional glass forming ability of these new alloys are discussed.
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61.43.Fs Glasses
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
81.05.Kf Glasses (including metallic glasses)

Low‐temperature in situ preparation of ferroelectric Pb(Zr0.55Ti0.45)O3 thin films by reactive sputtering

Xingjiao Li, Jianshe Liu, Yike Zeng, and Junwen Liang

Appl. Phys. Lett. 63, 2345 (1993); http://dx.doi.org/10.1063/1.110521 (3 pages) | Cited 10 times

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Ferroelectric thin films with a composition Pb(Zr0.55Ti0.45)O3 have been prepared on Pt‐coated Si substrates by a reactive sputtering technique at substrate temperatures as low as 250 °C. By means of x‐ray diffraction, titanium zirconium oxide was identified as one of the reaction products. Based on this fact, a possible Pb(Zr,Ti)O3 formation mechanism has been proposed. X‐ray diffraction patterns of these films show nearly no pyrochlore phase. Ferroelectric hysteresis loops show a remanent polarization of 25.6 μC/cm2 and a coercive field of 17.1 kV/cm.    
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81.15.Cd Deposition by sputtering
77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Step‐flow growth on strained surfaces

C. Ratsch and A. Zangwill

Appl. Phys. Lett. 63, 2348 (1993); http://dx.doi.org/10.1063/1.110522 (3 pages) | Cited 20 times

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A theoretical study is presented of the effect of misfit strain on the transition from step flow to island nucleation dominated epitaxial layer growth on a vicinal surface. The analysis generalizes a set of reaction‐diffusion equations used for homoepitaxy to include the fact that heteroepitaxial strain changes the Arrhenius barrier for diffusion and promotes the detachment of atoms from the edge of strained terraces and islands. The first effect is equivalent to changing the deposition flux; the latter can drive the system into a new layer growth mode characterized by moving steps that engulf very many very small islands. Experiments to test these predictions are suggested.
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68.55.-a Thin film structure and morphology

Crystal growth of C60 thin films on layered substrates

Katsumi Tanigaki, Sadanori Kuroshima, Jun‐ichi Fujita, and Thomas W. Ebbesen

Appl. Phys. Lett. 63, 2351 (1993); http://dx.doi.org/10.1063/1.110523 (3 pages) | Cited 46 times

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The process of the C60 thin film crystal growth on layered materials such as MoS2 and mica is studied in detail with a combination of atomic force microscopy (AFM) and reflection high‐energy electron diffractometry, and is compared to that on alkali‐halide (NaCl) substrates. AFM shows that a single crystal containing triangle‐shaped grains of 1–2 μm size with a (111) surface terrace is grown on the MoS2 substrate over a large area through a layer‐by‐layer process, while the grains on mica are 200–400 nm in size and distribute with some disorder in the orientation. The epitaxial characteristics of the C60 crystal growth on these layered substrates are discussed in comparison with that on alkali‐halides.
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68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Electrical conductivity studies of diamond films prepared by electron cyclotron resonance microwave plasma

S. Jin and T. D. Moustakas

Appl. Phys. Lett. 63, 2354 (1993); http://dx.doi.org/10.1063/1.110524 (3 pages) | Cited 20 times

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The electrical conductivity of diamond films, having different surface morphologies, was measured in the temperature range from 200 to 800 °C. The films were prepared by the electron cyclotron resonance plasma‐assisted CVD method (ECR‐PACVD) using CO/H2/O2 . We found that films with (111) surface morphology have electrical conductivity activation energies of between 0.3 and 0.4 eV, consistent with boron ionization energy in diamond. On the other hand, films with (100) morphology have an activation energy of 1.5 eV, consistent with the ionization energy of substitutional nitrogen. Due to their high solubility, boron and nitrogen are the most common impurities in natural and synthetic diamond. These data suggest that electrically active boron and nitrogen incorporation is correlated with the film growth along (111) and (100) directions, respectively.
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73.61.Cw Elemental semiconductors
71.55.Cn Elemental semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Can electrical deactivation of highly Si‐doped GaAs be explained by autocompensation?

S. Schuppler, D. L. Adler, L. N. Pfeiffer, K. W. West, E. E. Chaban, and P. H. Citrin

Appl. Phys. Lett. 63, 2357 (1993); http://dx.doi.org/10.1063/1.110500 (3 pages) | Cited 12 times

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Using near‐edge x‐ray absorption fine structure, the first experimental determination of Si atom concentrations occupying As sites in Si‐doped GaAs (100) is reported. The measurements reveal that at high doping levels (≳1019 cm−3) in molecular‐beam‐epitaxy‐grown samples, the number of such p‐type Si atoms is insufficient to account for the observed large reduction of free‐carriers.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.uf Ge and Si
78.70.Dm X-ray absorption spectra
72.80.Cw Elemental semiconductors

X‐ray photoemission characterization of thin epitaxial Fe silicide phases on Si(111)

U. Kafader, P. Wetzel, C. Pirri, and G. Gewinner

Appl. Phys. Lett. 63, 2360 (1993); http://dx.doi.org/10.1063/1.110501 (3 pages) | Cited 10 times

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Depending on preparation conditions, Fe silicides grown on Si(111) by means of solid phase epitaxy and molecular beam epitaxy show the formation of the bulk ϵ‐FeSi and β‐FeSi2 phases as well as epitaxially grown metastable CsCl‐ and CaF2‐type Fe silicides. The valence‐band of these Fe silicides are measured with monochromatized Al Kα x‐ray photoemission and angle resolved ultraviolet photoemission and are found to be in remarkable agreement with calculated densities of states.
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68.55.-a Thin film structure and morphology
73.20.At Surface states, band structure, electron density of states
79.60.Jv Interfaces; heterostructures; nanostructures

Critical conditions for achieving blue light emission from porous silicon

Xun Wang, G. Shi, F. L. Zhang, H. J. Chen, W. Wang, P. H. Hao, and X. Y. Hou

Appl. Phys. Lett. 63, 2363 (1993); http://dx.doi.org/10.1063/1.110502 (3 pages) | Cited 39 times

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By observing the luminescence micrographic images and measuring the decay behaviors of photoluminescence spectra, it is found that the blue light‐emitting porous silicon obtained by boiling water treatment behaves very similarly to the red light‐emitting sample. It is thus believed that the blue light emission is originated from the porous silicon skeleton rather than impurity contaminations. The achievement of blue light emission requires the proper control of the size of the Si nanostructures, effective passivation of the internal surfaces of porous silicon layer, and keeping a mechanically strong Si skeleton. A theoretical estimation and the experiments show that the simultaneous fulfillment of these conditions is quite critical, which explains the poor reproducibility of achieving blue emission experimentally.
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78.55.Hx Other solid inorganic materials
81.65.-b Surface treatments
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

High temperature ballistic transport observed in AlGaAs/InGaAs/GaAs small four‐terminal structures

Y. Hirayama and S. Tarucha

Appl. Phys. Lett. 63, 2366 (1993); http://dx.doi.org/10.1063/1.110799 (3 pages) | Cited 14 times

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Four‐terminal structures are fabricated by focused‐ion‐beam (FIB) scanning on an AlGaAs/InGaAs/GaAs modulation doped structure. The large carrier density of this system results in small depletion spreading and a 260‐nm‐square four‐terminal structure is successfully formed. The bend resistance of this structure indicates that ballistic coupling between two facing terminals remains up to room temperature. Thermal broadening of electron energy enhances the ballistic nature of the system at high temperature.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Ey III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Determining the electric field in [111] strained‐layer quantum wells

Richard L. Tober and Thomas B. Bahder

Appl. Phys. Lett. 63, 2369 (1993); http://dx.doi.org/10.1063/1.110478 (3 pages) | Cited 28 times

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The electric field in a [111] growth‐axis strained‐layer quantum well embedded in a p‐i‐n diode is determined by measuring the polarization vector in the quantum well. The polarization is determined from the critical reverse bias necessary to produce zero electric field in the quantum well. The critical reverse bias is obtained from electroreflectance spectra, which have quantum well optical features that exhibit a 180° phase change at flat band. A depletion model of the p‐i‐n diode with an embedded quantum well is used to relate the electric field in the quantum well to the applied bias and the polarization vector in the well.  
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78.66.Fd III-V semiconductors
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
42.79.Hp Optical processors, correlators, and modulators
42.65.Pc Optical bistability, multistability, and switching, including local field effects

Escape tunneling out of shallow multiple quantum wells studied by transient four‐wave mixing

G. von Plessen, J. Feldmann, E. O. Göbel, K. W. Goossen, D. A. B. Miller, and J. E. Cunningham

Appl. Phys. Lett. 63, 2372 (1993); http://dx.doi.org/10.1063/1.110479 (3 pages) | Cited 8 times

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We demonstrate that transient optical dephasing experiments on electrically biased, shallow multiple quantum wells offer the unique possibility of studying the first step in carrier sweep‐out, namely, the tunneling escape out of the individual quantum wells. We find that the electron tunneling times out of the quasibound n=1 quantum well states into the continuum states lie in the subpicosecond regime at high electric fields. In addition, the experimentally determined escape rate is resonantly enhanced when the quasibound n=1 quantum well state couples with the resonant n=2 continuum state originating from the second‐nearest neighbor well.
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73.40.Gk Tunneling
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.47.-p Spectroscopy of solid state dynamics

Realization of nearly two‐dimensional growth mode for AlP on Si(100) substrate by a low temperature migration enhanced epitaxy

H. Maruyama, K. Pak, K. Sakakibara, and H. Yonezu

Appl. Phys. Lett. 63, 2375 (1993); http://dx.doi.org/10.1063/1.110798 (3 pages)

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AlP layers were successfully grown on Si(100) substrates with a nearly two‐dimensional growth mode using a low temperature migration enhanced epitaxy. The reflection high‐energy electron diffraction intensity oscillations were observed at the initial growth stage although a three‐dimensional mode occurred at all times in the molecular beam epitaxy growth. The Auger electron spectroscopy measurement also showed that the nearly two‐dimensional growth mode proceeded from the start of the AlP growth.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Optical investigation of interwell coupling in strained Si1−xGex/Si quantum wells

S. Fukatsu and Y. Shiraki

Appl. Phys. Lett. 63, 2378 (1993); http://dx.doi.org/10.1063/1.110480 (3 pages) | Cited 25 times

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Photoluminescence is reported in strained Si1−xGex/Si(100) coupled double quantum well (CDQW) systems. Systematic red shift of luminescence energy was found in symmetric CDQWs with decreasing width of the Si barrier centered at the DQW, the characteristics of which were used to determine the band offsets. The total and valence‐band discontinuities, ΔEc+ΔEv=156 meV and ΔEv=149±1 meV, were obtained, suggesting that the band alignment is of type I for x=0.177. Variation of the inserted Si barrier width in asymmetric CDWs revealed well‐resolved spectral evolution due to the reduction in tunneling‐controlled carrier escape competing with the radiative recombination.
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78.66.Li Other semiconductors
78.55.Hx Other solid inorganic materials
73.40.Gk Tunneling
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Strong luminescence intensities in Al0.22Ga0.78As grown on misoriented (111)B GaAs

Albert Chin, T. M. Cheng, S. P. Peng, Ziad Osman, Utpal Das, and C. Y. Chang

Appl. Phys. Lett. 63, 2381 (1993); http://dx.doi.org/10.1063/1.110481 (3 pages) | Cited 9 times

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Strong enhancement in the luminescence intensity is observed in Al0.22Ga0.78As epitaxial layers grown on misoriented (111)B GaAs at 630 °C. For 3° misorientation, the luminescence intensity is almost 10 times that of (100) layers and the luminescence efficiency is an order of magnitude stronger than that of (100). (100) Al0.4Ga0.6As/GaAs quantum well laser diode structures grown under identical conditions with a low threshold current density of 150 A/cm2 are indications of excellent AlGaAs material quality. Electron mobility for 3° misoriented (111) Al0.25Ga0.75As is about 10% higher than that for side‐by‐side grown (100). The strong luminescence associated with a large red shift of 90 meV, the 10% mobility enhancement, and wirelike structure shown in transmission electron microscopy are indicative of the natural formation of quantized structures.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
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