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5 Dec 1994

Volume 65, Issue 23, pp. 2901-3024

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Quantum cascade laser: Temperature dependence of the performance characteristics and high T0 operation

Jerome Faist, Federico Capasso, Deborah L. Sivco, Albert L. Hutchinson, Carlo Sirtori, S. N. G. Chu, and Alfred Y. Cho

Appl. Phys. Lett. 65, 2901 (1994); http://dx.doi.org/10.1063/1.112524 (3 pages) | Cited 55 times

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The design and temperature dependence of the performance characteristics of a quantum cascade intersubband laser operating pulsed in the midinfrared (λ≂4.3 μm) are reported. The threshold current density varies exponentially with temperature [exp(T/T0)] from ≊6.0 kA/cm2 at 50 K to ≊9.3 kA/cm2 up to the maximum operating temperature (125 K) with a T0∼112 K. This weak temperature dependence, compared to interband lasers operating at similar wavelengths, is due to the intersubband nature of the laser transition, to the physics of optical phonons scattering, and to the negligible intersubband Auger transition rates. The measured peak optical power varies from 32 mW at 10 K to 18 mW at 80 K for a 1.2‐mm cavity length. The measured slope efficiency is 52 mW/A at 80 K which corresponds to an estimated differential quantum efficiency of ≂3.4×10−2 per facet per stage. © 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

Compact high‐efficiency carbon monoxide laser at 1 kW

G. Yu, H. J. Baker, N. A. S. Rodrigues, and D. R. Hall

Appl. Phys. Lett. 65, 2904 (1994); http://dx.doi.org/10.1063/1.112525 (3 pages) | Cited 2 times

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A fast‐axial‐flow, cryogenically cooled, carbon monoxide laser has been operated at 28% efficiency producing a continuous wave output power of 1.08 kW. The laser uses two cylindrical discharge sections, each 225 mm in length, which are excited by transverse radio‐frequency fields at 27 MHz in a linear stable optical resonator. A specific power output of 2.41 kW m−1 and an extraction power density of 9.41 W cm−3 have been attained by optimization of the transverse and longitudinal electrode configuration. © 1994 American Institute of Physics.  
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.-v Laser optical systems: design and operation

Novel parallel multijunction solar cell

Martin A. Green and Stuart R. Wenham

Appl. Phys. Lett. 65, 2907 (1994); http://dx.doi.org/10.1063/1.112526 (3 pages) | Cited 27 times

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A novel parallel multijunction solar cell is described which allows fundamental radiative recombination limits upon photovoltaic cell energy conversion efficiency to be approached more closely in good quality material than possible in a single‐junction device. However, the real advantage arises for poor quality material with the structure shown to be particularly tolerant of both impurity and grain boundary effects. A novel implementation approach is described for potentially high‐performance, low‐cost, thin‐film polycrystalline silicon solar cells. © 1994 American Institute of Physics.
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84.60.Jt Photoelectric conversion
73.50.Pz Photoconduction and photovoltaic effects
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Wavelength switching in pump‐diode‐modulated mode‐locked and Q‐switched Er‐fiber laser

O. G. Okhotnikov, F. M. Araújo, and J. R. Salcedo

Appl. Phys. Lett. 65, 2910 (1994); http://dx.doi.org/10.1063/1.112527 (3 pages) | Cited 2 times

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An Er‐doped fiber laser configuration is described which utilizes a coupled cavity terminated with Bragg reflectors with intracavity 1.48 μm laser diode used as pump source and modulator. This approach represents a minimal configuration for a mode‐locked and Q‐switched fully integrated fiber laser. Individual addressing of reflectors and fast wavelength switching can be obtained by current modulation of the laser diode in a dispersive compound resonator. © 1994 American Institute of Physics.
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42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.55.Wd Fiber lasers
42.60.Fc Modulation, tuning, and mode locking

Optical differentiator based on rapid collapse of Wannier–Stark localization due to space charge field screening

M. Hosoda, K. Tominaga, T. Watanabe, and K. Fujiwara

Appl. Phys. Lett. 65, 2913 (1994); http://dx.doi.org/10.1063/1.112528 (3 pages) | Cited 2 times

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An optical differentiator operation is demonstrated using a GaAs/AlAs short‐period superlattice near an optical absorption band edge. This operation is clearly explained by a rapid collapse of Wannier–Stark localization due to electric field screening by photogenerated space charges, because the screening causes a positive feedback loop between restoration of blueshifted wavelength of absorption band edge to the red side and an increase in optical absorption which causes an additional field screening. © 1994 American Institute of Physics.
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42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.65.Pc Optical bistability, multistability, and switching, including local field effects
78.66.Fd III-V semiconductors

Strong intensity attenuation of Raman scattering in proton‐exchanged LiNbO3 crystals

Xinglong Wu, Ming‐sheng Zhang, and Duan Feng

Appl. Phys. Lett. 65, 2916 (1994); http://dx.doi.org/10.1063/1.112529 (3 pages) | Cited 3 times

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Raman spectroscopy of protonated LiNbO3 crystal has been performed as a function of proton‐exchange time. At right angle scattering geometries, a strong (more than 50 times) intensity attenuation of Raman scattering was found in samples after 12–14 h proton treatment. A similar situation exists in the protonated LiTaO3 crystal after 8–10 h proton treatment. We attribute this anomalous attenuation tentatively to phonon localization‐related effects, resulting from the strongly disordered distribution of protons in the sample. © 1994 American Institute of Physics.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
61.72.up Other materials
63.20.kp Phonon-defect interactions

Self‐holding photochromic polymer Mach–Zehnder optical switch

Fumihiro Ebisawa, Mitsutoshi Hoshino, and Ken Sukegawa

Appl. Phys. Lett. 65, 2919 (1994); http://dx.doi.org/10.1063/1.112530 (3 pages) | Cited 38 times

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A self‐holding and optical–optical 2×2 switch using a Mach–Zehnder interferometer with a thermally irreversible photochromic (PC) guest/host polymer cladding is reported. The device was fabricated using a silica‐based integrated optic Mach–Zehnder interferometer with a PC cladding polymer. Cross‐bar switching was achieved by using ultraviolet (313 nm) and visible (≳500 nm) light. The switching state was self‐holding in the dark. Switching was observed with a crosstalk ratio of −12 dB and an excess loss of 7 dB at 1.55 μm. © 1994 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
42.70.Jk Polymers and organics

Reliability and degradation of organic light emitting devices

P. E. Burrows, V. Bulovic, S. R. Forrest, L. S. Sapochak, D. M. McCarty, and M. E. Thompson

Appl. Phys. Lett. 65, 2922 (1994); http://dx.doi.org/10.1063/1.112532 (3 pages) | Cited 287 times

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We present a simple encapsulation technique for organic light emitting devices (OLEDs). By studying the degradation of a population of OLEDs, we show that the lifetime of encapsulated devices is increased by more than two orders of magnitude over that of unencapsulated devices. In both cases, degradation is primarily due to the formation of nonemissive regions, or dark spot defects. By studying the structure and evolution of the dark spots, we infer that the growth of electrode defects limits device lifetime. Hermetic packaging of OLEDs is essential if they are to be used in commercially viable flat panel displays. © 1994 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.66.Qn Polymers; organic compounds
85.40.Qx Microcircuit quality, noise, performance, and failure analysis

Giant photoexpansion in As2S3 glass

H. Hisakuni and K. Tanaka

Appl. Phys. Lett. 65, 2925 (1994); http://dx.doi.org/10.1063/1.112533 (3 pages) | Cited 101 times

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When illuminated with a focused beam from He‐Ne lasers, As2S3 films with thickness of ∼50 μm exhibit the thickness expansion reaching to 3 μm, which is approximately 10 times as great as that expected from the conventional photoexpansion phenomenon. The enhancement seems to be caused by photorelaxation of strain generated by photoexpansion. © 1994 American Institute of Physics.
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62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.43.Fs Glasses

Variable delay dual wavelength picosecond optical pulse generation using an actively mode‐locked multichannel grating cavity laser

B. Zhu and I. H. White

Appl. Phys. Lett. 65, 2928 (1994); http://dx.doi.org/10.1063/1.112534 (3 pages) | Cited 9 times

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Two optical pulse trains are generated at different wavelengths with a programmable delay between them, using active mode‐locking of a multichannel grating cavity laser. For a channel separation of 2.2 nm, pulses with a duration of 60 ps and with a spectral width of 11.6 GHz have been obtained at a repetition rate of 1.78 GHz. The pulse width and power are stable to within 6%, irrespective of delay for a relatively wide range of dc bias conditions. © 1994 American Institute of Physics.  
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
42.55.Rz Doped-insulator lasers and other solid state lasers

Photodetector for microwave signals based on the synchronous drift of photogenerated carriers with a moving interference pattern

D. Dolfi, Th. Merlet, A. Mestreau, and J.‐P. Huignard

Appl. Phys. Lett. 65, 2931 (1994); http://dx.doi.org/10.1063/1.112536 (3 pages) | Cited 10 times

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We present the principle of a new photodetector based on the synchronous drift in a semiconductor of photogenerated carriers with a moving interference pattern. It provides a large detection volume which could be suitable for the optical generation of microwave signals. A theoretical analysis is detailed and followed by an experimental demonstration in a MBE grown GaAs layer illuminated with a moving interference pattern. We study the evolution of the detected signal at frequency f=1.6 GHz as a function of applied electric field, carrier lifetime, and fringe period. © 1994 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Dw Photodiodes; phototransistors; photoresistors
72.40.+w Photoconduction and photovoltaic effects

Observation of nonlinear accompanying electric potential wave in piezoelectric crystals

Wenhua Jiang and Gonghuan Du

Appl. Phys. Lett. 65, 2934 (1994); http://dx.doi.org/10.1063/1.112539 (3 pages)

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The theory of three‐field acoustic interactions in nonlinear piezoelectric crystals predicts that the second‐harmonic acoustic wave is accompanied by the second‐harmonic electric potential wave due to the electroacoustic nonlinearities of the media. An experiment to demonstrate the phenomenon carried out for crystal LiNbO3 is described in this letter. Ultrasonic waves excited by a 30 MHz quartz transducer propagate along the z direction of LiNbO3 crystal. The nonlinear electric potential wave accompanying with the acoustic wave is directly detected by use of the capacitive detector. To the author’s knowledge, this kind of observation has not been made before. © 1994 American Institute of Physics.
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77.65.Bn Piezoelectric and electrostrictive constants
77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Influence of the electric field on the quasibookshelf stripe deformation in an electroclinic liquid crystal

G. P. Crawford, R. E. Geer, J. Naciri, R. Shashidhar, and B. R. Ratna

Appl. Phys. Lett. 65, 2937 (1994); http://dx.doi.org/10.1063/1.112540 (3 pages) | Cited 30 times

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A quantitative study of the effect of electric field on the stripe domains formed by layer deformation in chiral smectic A liquid crystals is presented. X‐ray diffraction studies reveal that the angle between the layer normals in adjacent stripe domains increases with increasing electric field. A simple model is presented to derive the true molecular tilt angle from optical transmission measurements. The relationship between the optical tilt angle and the tilt angle evaluated from x‐ray measurements of the smectic layer thickness indicates that the molecules are tilting as rigid rods. © 1994 American Institute of Physics.
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61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
42.70.Df Liquid crystals

γ‐Al2O3 formation from pulsed‐laser irradiated sapphire

Siqi Cao, A. J. Pedraza, D. H. Lowndes, and L. F. Allard

Appl. Phys. Lett. 65, 2940 (1994); http://dx.doi.org/10.1063/1.112960 (3 pages) | Cited 13 times

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High‐resolution transmission electron microscopy was used to examine the effect of laser irradiation of sapphire (single crystalline α‐Al2O3). It was observed that laser‐melted material resolidified as γ‐Al2O3 epitactically grown on the (0001) plane of α‐Al2O3 having an orientation relationship (0001)α//(111)γ and [0110]α//[110]γ. The interface between unmelted α‐Al2O3 and resolidified γ‐Al2O3 is atomically flat with steps of one to a few close‐packed oxygen layers. The high thermal gradient in the α‐Al2O3 did not produce any interfacial dislocations. However, pronounced lattice distortions existed in the resolidified γ‐Al2O3. It is argued that the very rapid cooling rate present during solidification prevents the ordering of Al atoms that is required for the formation of the stable α‐Al2O3 phase. © 1994 American Institute of Physics.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
64.70.D- Solid-liquid transitions
81.30.Fb Solidification

Importance of steps in heteroepitaxy: The case of aluminum on silicon

Marek Sosnowski, Samuel Ramac, Walter L. Brown, and Young O. Kim

Appl. Phys. Lett. 65, 2943 (1994); http://dx.doi.org/10.1063/1.112541 (3 pages) | Cited 6 times

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We have observed dominant epitaxial growth of Al(100) films on chemically cleaned, hydrogen terminated, off‐oriented Si(111). The films were deposited by thermal evaporation at room temperature in ultrahigh vacuum. X‐ray diffraction shows sharp and intense Al(200) diffraction, enhanced by postdeposition annealing. Crystal quality and the dominance of Al(100) structure depend strongly on the substrate treatment and the off‐cut angle, both of which control the steps on the Si(111) surface. The steps were found responsible for the epitaxial alignment of the film and the substrate lattices. Details of this alignment were observed in transmission electron microscopy cross‐sectional images of the interface. Our findings are in contrast to previously published results which indicate epitaxial growth of Al(111) on Si(111). © 1994 American Institute of Physics.
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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

Infrared wavelength and temperature dependence of optically induced terahertz radiation from InSb

S. C. Howells, S. D. Herrera, and L. A. Schlie

Appl. Phys. Lett. 65, 2946 (1994); http://dx.doi.org/10.1063/1.112542 (3 pages) | Cited 20 times

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Results of the temperature and infrared wavelength (0.8, 1.4, and 1.9 μm) dependence of terahertz radiation generated from both undoped and Te‐doped InSb irradiated with ≊125 fs laser pulses are reported. Undoped InSb shows a substantial change in the spectral content of the terahertz radiation between 80 and 260 K, while the spectrum of Te‐doped InSb remains nearly unchanged, an effect attributed to its mobility being dominated by impurity scattering. Also, the terahertz radiation from undoped InSb at 80 K is dependent on the irradiating wavelength, with both a higher frequency spectrum and much larger amplitude generated at longer wavelengths. No such effect is observed at 260 K. © 1994 American Institute of Physics.
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78.47.-p Spectroscopy of solid state dynamics
72.80.Ey III-V and II-VI semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Off‐diagonal orthorhombic‐symmetry elastic constants

Sudook Kim

Appl. Phys. Lett. 65, 2949 (1994); http://dx.doi.org/10.1063/1.112543 (2 pages) | Cited 1 time

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We derive analytical expressions for off‐diagonal elastic stiffnesses C12, C13, and C23 in terms only of easily and precisely measurable diagonal elastic stiffnesses and Young moduli. We verify the expressions for several symmetry classes: cubic (Li), hexagonal (Zn), tetragonal (In), orthorhombic (Ga), and a weakly orthorhombic fiber composite: B/Al.  
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62.20.D- Elasticity

Nitrogen in the isotopically enriched 12C diamond

Shigang Zhang, M. E. Zvanut, Y. K. Vohra, and Suresh S. Vagarali

Appl. Phys. Lett. 65, 2951 (1994); http://dx.doi.org/10.1063/1.112544 (3 pages) | Cited 1 time

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An electron paramagnetic resonance (EPR) characterization study of isotopically enriched 12C diamond grown by General Electric has been carried out. While other commonly used techniques detect no nitrogen in this diamond, the clear EPR spectrum consistently measured a nitrogen concentration of about 0.05 ppm by calibration against a few standards. The concentration is about 2 orders of magnitude lower than that of a few natural IIa diamonds and over 4 orders of magnitude smaller than that of a typical yellow Ib diamond. The 12C diamond is evaluated to be ideal for research of diamonds under high pressure as well as irradiated diamonds. Both the experimental line shape and second moment do not support a random nitrogen distribution in this diamond. Instead, we found that nitrogen atoms tend to stay apart from one another. This uniformly dispersed nitrogen distribution is a new state of nitrogen found in diamond. © 1994 American Institute of Physics.
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61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
61.72.S- Impurities in crystals

Asymmetric tilt interface induced by 60° misfit dislocation arrays in GaSb/GaAs(001)

J. M. Kang, Suk‐Ki Min, and A. Rocher

Appl. Phys. Lett. 65, 2954 (1994); http://dx.doi.org/10.1063/1.112502 (3 pages) | Cited 11 times

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Transmission electron microscopy of GaSb film grown on (001) GaAs revealed regular 60° misfit dislocation arrays in abnormally large and irregularly shaped GaSb islands. Having a same orientation of the Burgers vector, the 60° dislocations induce an asymmetric tilt interface. Calculations using anisotropic elasticity show that this interface has lower elastic energy than the symmetric interface relaxed by 60° dislocations of alternating orientations. When 60° dislocations are generated at the leading edge of growing islands, a particular orientation that assists the bending of atomic planes to the free surface of islands is preferred for a partial elastic relief of the misfit strain. © 1994 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.-a Thin film structure and morphology
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Production and characterization of smooth, hydrogen‐terminated diamond C(100)

Brian D. Thoms, Michael S. Owens, James E. Butler, and Clifford Spiro

Appl. Phys. Lett. 65, 2957 (1994); http://dx.doi.org/10.1063/1.112503 (3 pages) | Cited 68 times

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We report the production of smooth and well‐ordered C(100) surfaces by exposure to a pure hydrogen plasma. A two domain 2×1 surface reconstruction is observed by low energy electron diffraction with half‐order spots visible using incident electrons with energies as low as 13 eV. High‐resolution electron energy loss spectroscopy reveals a large enhancement in specular reflectivity of low energy electrons following plasma treatment. The hydrogenated surface is stable in air and free of adsorbed hydrocarbons upon insertion into ultrahigh vacuum. © 1994 American Institute of Physics.
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81.65.-b Surface treatments
68.35.B- Structure of clean surfaces (and surface reconstruction)

Novel chemical routes to silicon‐germanium‐carbon materials

John Kouvetakis, Michael Todd, D. Chandrasekhar, and David J. Smith

Appl. Phys. Lett. 65, 2960 (1994); http://dx.doi.org/10.1063/1.112504 (3 pages) | Cited 16 times

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We report the use of novel molecular precursors and ultrahigh vacuum chemical vapor deposition techniques to synthesize solid solutions of cubic SiC‐GeC and diamond‐structure Si1−x−yGexCy materials. Thin films with composition Si0.37Ge0.13C0.50 were deposited on Si by thermal decomposition of Ge[Si(CH3)3]4 at 650–700 °C. Electron microscope observations showed a polycrystalline zinc‐blende‐type structure and infrared (IR) analyses revealed carbide‐type Si‐C and Ge‐C vibrations. The Si1−x−yGexCy (y≳2%) alloys were deposited at 550–600 °C on Si and SiO2 by interactions of (1) C(SiH3)4 and GeH4; (2) CH3GeH3 and SiH4; and (3) CH3GeH3 with mixtures of GeH4 and SiH4. A homogeneous alloy phase of composition Si56Ge30C14 with diamond cubic structure was obtained from reaction 1. Reactions 2 and 3 produced films with carbon compositions ranging from 2 to 27 at. %. The materials containing less than 10% carbon appeared to be exclusively diamond cubic, whereas those with greater carbon compositions showed mixtures of diamond cubic and carbide phases as indicated by vibrational and structural characterization. Secondary ion mass spectrometry experiments revealed that all materials had excellent chemical purity. © 1994 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.-a Thin film structure and morphology

Characteristics of high quality ZnO thin films deposited by pulsed laser deposition

V. Craciun, J. Elders, J. G. E. Gardeniers, and Ian W. Boyd

Appl. Phys. Lett. 65, 2963 (1994); http://dx.doi.org/10.1063/1.112478 (3 pages) | Cited 90 times

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Thin films of ZnO have been deposited on glass and silicon substrates by the pulsed laser deposition technique employing a KrF laser (λ=248 nm). The influence of the deposition parameters, such as substrate temperature, oxygen pressure, and laser fluence on the properties of the grown films, has been studied. All the films grown over a rather wide range of deposition conditions were found to be optically transparent, electrically conductive, and c‐axis oriented, with the full width at half‐maximum (FWHM) of the (002) x‐ray reflection line being very often less than 0.25°. Under optimized laser fluence and oxygen pressure conditions, highly c‐axis oriented films having a FWHM value less than 0.15° and optical transmittance around 85% in the visible region of the spectrum have been grown at a substrate temperature of only 350 °C. These are among the best properties yet reported for ZnO films grown by any technique at such a low temperature. © 1994 American Institute of Physics.  
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81.15.Fg Pulsed laser ablation deposition
68.55.-a Thin film structure and morphology
78.66.Li Other semiconductors
73.61.Le Other inorganic semiconductors

Ordering induced by swift ions in semicrystalline polyvinylidene fluoride

R. Percolla, L. Calcagno, G. Foti, and G. Ciavola

Appl. Phys. Lett. 65, 2966 (1994); http://dx.doi.org/10.1063/1.112479 (3 pages) | Cited 8 times

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Thin semicrystalline polyvinylidene fluoride foils are irradiated by swift ions (60 MeV carbon) with a dose in the range 10–300 kGy. After irradiation a change of crystalline structure is observed as detected by x‐ray diffraction measurements. Diffraction analysis or irradiated polyvinylidene fluoride shows a structural order along the (020) atomic planes. This effect appears when a threshold dose value of about 100 kGy is reached and saturates at higher dose (≥250 kGy). Differential scanning calorimetry measurements performed in the same dose range do not show any change in the melting enthalpy (56.0 J/g) of the alpha‐phase polyvinylidene fluoride. © 1994 American Institute of Physics.
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61.80.Jh Ion radiation effects

Second‐harmonic generation in asymmetric Si/SiGe quantum wells

M. Seto, M. Helm, Z. Moussa, P. Boucaud, F. H. Julien, J.‐M. Lourtioz, J. F. Nützel, and G. Abstreiter

Appl. Phys. Lett. 65, 2969 (1994); http://dx.doi.org/10.1063/1.113028 (3 pages) | Cited 22 times

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The observation of infrared second‐harmonic generation in asymmetric Si/SiGe p‐doped quantum wells is reported. The generated signal stems entirely from valence intersubband transitions, since bulk Si, with an inversion symmetric crystal structure, has a zero second‐order susceptibility. The experiments were performed using a Q‐switched CO2 laser operating at 10.56 μm and give a nonlinear susceptibility of 5×10−8 m/V. © 1994 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.66.Li Other semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Resonant Raman scattering and spectral ellipsometry on InAs/GaSb superlattices with different interfaces

D. Behr, J. Wagner, J. Schmitz, N. Herres, J. D. Ralston, P. Koidl, M. Ramsteiner, L. Schrottke, and G. Jungk

Appl. Phys. Lett. 65, 2972 (1994); http://dx.doi.org/10.1063/1.112480 (3 pages) | Cited 20 times

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We have used Raman spectroscopy and spectral ellipsometry to investigate InAs/GaSb short‐period superlattices (SLs), grown by molecular‐beam epitaxy, with either InSb‐ or GaAs‐like interfaces. Room‐temperature ellipsometric measurements show spectral features in the dielectric function due to the E1 and E1+Δ1 interband transitions of GaSb and InAs. For SLs with small InAs layer thicknesses (4 ML InAs/10 ML GaSb) the critical point energies are found to depend on the type of interfacial bonding, with an energy shift of up to 50 meV observed between SLs with GaAs‐ and InSb‐like interfaces. Resonant Raman measurements show a pronounced enhancement in scattering efficiency for the superlattice phonons and, in particular, for the interface modes for incident photon energies matching the critical point energies of the SL. © 1994 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
68.35.Ja Surface and interface dynamics and vibrations
68.55.-a Thin film structure and morphology
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