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16 Dec 1991

Volume 59, Issue 25, pp. 3207-3335

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Time‐division multiplexing by a photoconducting antenna array

N. M. Froberg, B. B. Hu, X.‐C. Zhang, and D. H. Auston

Appl. Phys. Lett. 59, 3207 (1991); http://dx.doi.org/10.1063/1.105733 (3 pages) | Cited 3 times

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When a photoconducting antenna array is illuminated by a subpicosecond laser pulse, the spatial profile of the applied bias field is mapped onto the temporal waveform of the radiated electric field. This property allows the array to function as a multiplexer, in which parallel electronic data are converted to a sequence of radiated pulses.
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42.79.Sz Optical communication systems, multiplexers, and demultiplexers
85.60.-q Optoelectronic devices

New modulator for far‐infrared light: Integrated mirror optical switch

J. Stiens, M. Kuijk, R. Vounckx, and G. Borghs

Appl. Phys. Lett. 59, 3210 (1991); http://dx.doi.org/10.1063/1.105734 (3 pages) | Cited 9 times

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We report on the first prototype IMOS (integrated mirror optical switch), FIR (far‐infrared: 8–12 μm) light modulator. The operation of this type of modulator is based on the reflection properties of a high density, thin electron sheet in semiconductors. The present prototype was built to give experimental backing for earlier theoretical predictions. Low electric power (4 W) and low voltage (12 V) operation have been achieved. A modulation depth of about 30% and a 3 dB frequency of 400 kHz were obtained.
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42.79.Hp Optical processors, correlators, and modulators
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.82.-m Integrated optics

Optical strip waveguides in KNbO3 formed by He ion implantation

D. Fluck, P. Günter, R. Irmscher, and Ch. Buchal

Appl. Phys. Lett. 59, 3213 (1991); http://dx.doi.org/10.1063/1.105735 (3 pages) | Cited 27 times

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Permanent optical strip waveguides in single crystals of KNbO3 were produced with MeV He ion implantation. Guided TE00 modes were observed and the propagation losses were characterized at the wavelengths of 514, 632, and 860 nm. Waveguide propagation losses of 1.4 dB/cm were measured at 632 nm.
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42.79.Gn Optical waveguides and couplers
42.82.-m Integrated optics

High contrast, submilliwatt power InGaAs/GaAs strained‐layer multiple‐quantum‐well asymmetric reflection modulator

R. Jin, G. Khitrova, H. M. Gibbs, C. Lowry, and N. Peyghambarian

Appl. Phys. Lett. 59, 3216 (1991); http://dx.doi.org/10.1063/1.105736 (3 pages) | Cited 10 times

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A high contrast, low power optical reflection modulator with an InGaAs/GaAs strained‐layer multiple quantum well (MQW) nonlinear spacer is demonstrated. Taking advantage of large absorptive and dispersive nonlinearities near the exciton peak, on/off contrast ratios exceeding 29 dB are achieved with submilliwatt pump powers at room temperature.
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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
42.79.Hp Optical processors, correlators, and modulators
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Quantum well width and In composition effects on the operating characteristics of InGaAs/GaAs strained single quantum well diode lasers

R. Ben‐Michael, D. Fekete, and R. Sarfaty

Appl. Phys. Lett. 59, 3219 (1991); http://dx.doi.org/10.1063/1.105737 (3 pages) | Cited 5 times

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In this work we study the effect of strain on the performance of highly strained InxGa1−xAs/GaAs/GaAlAs quantum well lasers (SQWL). We changed the indium concentration and the QW width and found that the threshold current density, Jth, is minimal with x∼0.4 when the width of the QW is 20 Å. For x=0.3 the minimal Jth was obtained with a 90 Å active layer. The best performing laser reported in this work has Jth=68 A/cm2 emitting at 1.063 μm with cavity length of 2022 μm. Comparison with GaAs/GaAlAs lasers is possible because both structures have the same optical mode confinement, and the comparison shows that SQWLs have indeed lower Jth, but the improvement in Jth with the strain is not as dramatic as predicted theoretically.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Phase‐locked ridge waveguide InGaAs‐GaAs‐AlGaAs strained‐layer quantum well heterostructure laser arrays

K. J. Beernink, L. M. Miller, T. M. Cockerill, and J. J. Coleman

Appl. Phys. Lett. 59, 3222 (1991); http://dx.doi.org/10.1063/1.105738 (3 pages)

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We report the characteristics of separate confinement heterostructure InGaAs/GaAs/AlGaAs strained‐layer quantum well heterostructure (λ≳1 μm) ridge waveguide laser arrays grown by metalorganic chemical vapor deposition, and etched by reactive ion etching. The ten element arrays have ridge widths of 4 μm on 8 μm centers. Several etch depths are examined, covering the range from gain‐guided to strongly index‐guided elements. For these structures, values of effective index step, Δneff, below ∼6×10−3 are necessary to achieve interelement coupling. For Δneff=1.3×10−3, the devices lase in the highest array mode up to ∼1.5 times threshold with a nearly diffraction‐limited double‐lobed far‐field pattern. For higher currents, additional structure in the far‐field pattern is observed, and is accompanied by splitting of the longitudinal modes due to operation in additional array modes.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
85.60.Jb Light-emitting devices

Lithographic spiral antennas at short wavelengths

E. N. Grossman, J. E. Sauvageau, and D. G. McDonald

Appl. Phys. Lett. 59, 3225 (1991); http://dx.doi.org/10.1063/1.105739 (3 pages) | Cited 26 times

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We have extended the high efficiency of lithographic antennas to mid‐infrared wavelengths. Pattern measurements made at 9.5 μm wavelength on a 65°, self‐complementary, spiral antenna exhibit a ratio of response to orthogonal linear polarizations of 1.35 dB, a beamwidth of 85° (3 dB full width), a directivity of 8.2 dB, and surprisingly, a close resemblance to the theoretical pattern for a 65° spiral in free space. Direct detection measurements made with an ambient temperature blackbody source yield an antenna efficiency of 52±7%, when corrected for incomplete filling of the antenna beam by the source, at a mean effective wavelength of 19 μm.
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42.82.-m Integrated optics
85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.-q Optoelectronic devices

ZnSe‐ZnSSe electro‐optic waveguide modulators

M. A. Haase, H. Cheng, D. K. Misemer, T. A. Strand, and J. M. DePuydt

Appl. Phys. Lett. 59, 3228 (1991); http://dx.doi.org/10.1063/1.105740 (2 pages) | Cited 19 times

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Rib waveguides have been fabricated in the ZnSe‐ZnSSe material system, grown by molecular beam epitaxy on GaAs substrates. Using Schottky barrier contacts, rib‐waveguide optical phase modulators have been demonstrated and the strength of the linear electro‐optic (Pockels) effect has been measured. A change in the index of refraction of Δn/ΔF=±1.7×10−9 cm/V has been attained for 633 nm light. This translates to a maximum Δn of 0.0008. Rib waveguides with losses as low as 0.66 cm−1 have been measured.
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42.79.Hp Optical processors, correlators, and modulators
42.79.Gn Optical waveguides and couplers

Approximate expressions for modulation speed and threshold for performance optimization of biaxially compressive strain quantum‐well lasers

Kerry J. Vahala and Chung‐en Zah

Appl. Phys. Lett. 59, 3230 (1991); http://dx.doi.org/10.1063/1.105741 (3 pages) | Cited 1 time

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Simple analytical expressions for transparency, threshold, and relaxation oscillation corner frequency are derived for biaxial strain quantum‐well lasers. An optimal operating point loss for high speed operation (in the absence of nonlinear gain) is established which varies as the square root of the number of quantum wells. The corresponding relaxation oscillation frequency is found to depend only on fundamental quantities. Its power dependence is ☒νR☒max☒ = ☒87 GHz√μm3☒mW☒ (Powerout/Vmode)1/2] where Vmode is the mode volume.
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42.55.Px Semiconductor lasers; laser diodes

Broadband optical detection of ultrasound by two‐wave mixing in a photorefractive crystal

R. K. Ing and J.‐P. Monchalin

Appl. Phys. Lett. 59, 3233 (1991); http://dx.doi.org/10.1063/1.105742 (3 pages) | Cited 47 times

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A method which allows broadband (from typically 1 KHz) optical detection of ultrasound with large light gathering from a scattering surface is presented. The wave scattered by the surface is mixed inside a BaTiO3 photorefractive crystal with a pump wave directly derived from the laser to provide a sideband‐free reference wave. A polarization configuration which provides sensitive and linear ultrasonic displacement detection is described. This method is demonstrated by detecting laser generated ultrasound.
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43.35.Yb Ultrasonic instrumentation and measurement techniques
43.35.Zc Use of ultrasonics in nondestructive testing, industrial processes, and industrial products
43.35.Sx Acoustooptical effects, optoacoustics, acoustical visualization, acoustical microscopy, and acoustical holography
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Velocity measurements in polyetheretherketone‐carbon fiber composite using excimer laser generated ultrasound

S. J. Ablett, P. E. Dyer, B. L. Tait, and J. A. Barnes

Appl. Phys. Lett. 59, 3236 (1991); http://dx.doi.org/10.1063/1.105743 (3 pages)

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It is demonstrated that KrF laser ablation provides a suitable source for short pulse ultrasound generation in polyetheretherketone (PEEK)‐carbon fiber composite. Measurements of plane wave velocities have been made on thin single laminae (∼130 μm thick) and multiple ply laminates of this anisotropic composite. Velocities for propagation at various angles with respect to the fiber axis have been measured and are shown to be in good agreement with theoretical calculations based on mechanical modulii.
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62.65.+k Acoustical properties of solids
62.80.+f Ultrasonic relaxation

Electron drift velocities in xenon and xenon‐nitrogen gas mixtures

E. L. Patrick, M. L. Andrews, and A. Garscadden

Appl. Phys. Lett. 59, 3239 (1991); http://dx.doi.org/10.1063/1.105744 (2 pages) | Cited 5 times

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The drift velocity of an electron swarm in pure xenon gas (99.995% pure) and xenon gas mixtures, containing 0.1%, 1%, and 10% nitrogen additive, was measured in a pulsed‐Townsend drift tube in order to observe the effects of the additives on electron mobility, and to demonstrate negative differential conductivity. The digitized signal was analyzed by a microcomputer to produce swarm drift time measurements. The amount of nitrogen necessary to perturb the electron drift velocity in pure xenon is implied from these measurements.
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51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)
52.20.Fs Electron collisions
52.80.-s Electric discharges

Correlation of texture with electromigration behavior in Al metallization

D. B. Knorr, D. P. Tracy, and K. P. Rodbell

Appl. Phys. Lett. 59, 3241 (1991); http://dx.doi.org/10.1063/1.105745 (3 pages) | Cited 88 times

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Aluminum films deposited at three different conditions, such that texture is the only microstructural variable, were tested for electromigration behavior. Texture analysis shows that random and (111) fiber texture components are present in the films deposited by both partially ionized beam (PIB), physical vapor deposition and sputtering. Two parameters are required to properly quantify the texture: (111) volume fraction and the distribution (half‐width) of the (111) fiber component. As the (111) texture becomes stronger, the median time to failure increases, while the failure standard deviation decreases. Previous texture correlations are based on incomplete information, so they cannot predict electromigration behavior in all cases.
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81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.15.Cd Deposition by sputtering
85.40.Qx Microcircuit quality, noise, performance, and failure analysis

Stress relaxation and stability of sputtered carbon thin films

V. Raman and K. R. Coffey

Appl. Phys. Lett. 59, 3244 (1991); http://dx.doi.org/10.1063/1.106398 (3 pages) | Cited 3 times

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Stress measurements were performed on sputtered carbon films deposited on Si substrates in the temperature range from room temperature to 350 °C. Both hydrogenated and nonhydrogenated carbon films, ∼100 nm in thickness, were investigated. The stress relaxation kinetics were investigated for films tested in air and in the presence of an inert environment. The experimental data show distinct differences for tests performed in these two environments. Microscopic examination revealed that films tested in air show local loss of carbon following a thermal cycle whereas the films tested in argon show good stability and remain well adhered to the substrate
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81.15.Cd Deposition by sputtering
81.40.Gh Other heat and thermomechanical treatments

Ion induced chemical bonding of carbon with Ta as studied by Auger electron spectroscopy and slow electron energy loss spectroscopy

J. K. N. Sharma, Santanu Bera, and B. R. Chakraborty

Appl. Phys. Lett. 59, 3247 (1991); http://dx.doi.org/10.1063/1.105746 (2 pages) | Cited 1 time

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The chemical bonding of contaminants like carbon and oxygen on the surface of Ta and Ta2O5 films due to Ar+ ion bombardment during sputter etching, has been studied using Auger electron spectroscopy and slow electron energy loss spectroscopy. Finger printing of C KLL peak shows that the energy separation between the major positive‐going and negative‐going excursions, which is 23 eV in the pure graphitic form, reduces to 6 eV indicating the carbide formation after ion bombardment. It is assumed that the chemical reaction is initiated by an increase in π electrons in the graphite due to ion bombardment. The carbide formation is found to be much less effected in Ta2O5 films which has been attributed to the absence of free d electrons of Ta in the oxide.
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61.80.Jh Ion radiation effects
68.35.Dv Composition, segregation; defects and impurities
81.05.Bx Metals, semimetals, and alloys

Endotaxial growth of CoSi2 within (111) oriented Si in a molecular beam epitaxy system

T. George and R. W. Fathauer

Appl. Phys. Lett. 59, 3249 (1991); http://dx.doi.org/10.1063/1.105747 (3 pages) | Cited 15 times

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A new mode of growth is reported in which buried metallic layers can be fabricated within a single‐crystal semiconductor through preferential subsurface growth on previously‐grown ‘‘seed’’ regions. The deposition of Co at 800 °C at a rate of 0.01 nm/s on (111) Si substrates containing buried CoSi2 columns 40–100 nm below the Si surface results in the growth and coalescence of these subsurface columns. The formation of a CoSi2 layer on the Si surface is suppressed by this growth mode. It is proposed that the high diffusion rate of Co at 800 °C, coupled with the high growth rate of CoSi2 at the subsurface columns, is responsible for this preferred ‘‘endotaxial’’ growth mode. This growth technique was used to produce a continuous buried single‐crystal layer of CoSi2 under a single‐crystal Si capping layer.
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68.55.-a Thin film structure and morphology
81.10.-h Methods of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation

Suppression of Al‐Ga interdiffusion by a WNx film on an AlxGa1−xAs/AlAs superlattice structure

E. L. Allen, C. J. Pass, M. D. Deal, J. D. Plummer, and V. F. K. Chia

Appl. Phys. Lett. 59, 3252 (1991); http://dx.doi.org/10.1063/1.105748 (3 pages) | Cited 8 times

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Undoped AlAs/AlxGa1−xAs superlattice structures were grown by molecular beam epitaxy and annealed under Si3N4, SiO2, or WNx encapsulant films, both with and without the presence of a 120Sn implant. Enhancement of the Al‐Ga interdiffusion coefficient occurred under the Si3N4 and SiO2 films due to indiffusion of Si from the films. Enhancement was even greater during diffusion of the Sn implant. In both cases intermixing enhancement was due to the Fermi level effect. Underneath the WNx film, however, interdiffusion was suppressed even in the presence of the Sn dopant.
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66.30.J- Diffusion of impurities
66.30.Ny Chemical interdiffusion; diffusion barriers
61.72.jd Vacancies
61.72.jj Interstitials
68.35.Fx Diffusion; interface formation

Discrepancies between photocurrent and absorption spectroscopies in intersubband photoionization from GaAs/AlGaAs multiquantum wells

E. Rosencher, E. Martinet, F. Luc, Ph. Bois, and E. Böckenhoff

Appl. Phys. Lett. 59, 3255 (1991); http://dx.doi.org/10.1063/1.105749 (3 pages) | Cited 18 times

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Intersubband transitions between a bound state and extended states in GaAs/AlGaAs multiquantum wells are studied by simultaneous absorption and photocurrent spectroscopy under different electric field conditions. It is found that both types of spectra exhibit different line shapes, with the photocurrent maximum occurring at lower photon energy than in absorption spectra. Moreover, there is a blue shift of absorption peak and a red shift of photocurrent peak with increasing electric fields. These results suggest that a sequential mechanism is involved in the photocurrent collection from the quantum well. The blue shift is then well fitted by a quadratic Stark effect and the red shift by a barrier lowering mechanism.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

Use of surface grooves to control ordering in GaAsP

G. S. Chen and G. B. Stringfellow

Appl. Phys. Lett. 59, 3258 (1991); http://dx.doi.org/10.1063/1.105750 (3 pages) | Cited 9 times

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GaAs1−xPx with 0.4≤x≤0.85 forms the CuPt ordered structure during organometallic vapor phase epitaxy (OMVPE). Only the (111) and (111) variants are observed for growth on (001)‐oriented substrates. The mechanism by which ordering occurs is only now being discovered. Total energy calculations, including the effects of surface reconstruction, indicate that the phenomenon can be explained purely on the basis of energy considerations. Indirect evidence indicates that kinetic factors, including processes occurring at steps propagating across the surface in the two‐dimensional growth mode, control ordering. In this work, GaAs1−xPx layers have been grown by OMVPE on (001)‐oriented GaAs0.6P0.4‘‘substrates.’’ In order to examine the effects of surface kinetic factors, the substrates were first patterned with [110]‐oriented grooves 5 μm wide and a fraction of a micron deep. The groove is used to provide a source of steps moving in opposite directions from the two edges. Transmission electron diffraction reveals the formation of large domains of the two variants that meet in the center of the groove. A surprising feature is the presence of a region in the groove with absolutely no ordering. Tracing the surface shape during growth using a superlattice structure indicates that the disordered region is due to growth on {511} facets. The domains formed after the groove is filled are very large, several square microns in cross‐sectional area and extending along the entire length of the groove. These results demonstrate that natural ordering in GaAsP, an alloy with mixing on the group V sublattice, can be controlled by regulating the propagation of steps during growth, exactly as for GaInP where mixing is on the group III sublattice.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Ordering effects on the electrical characteristics of Ga0.5In0.5P grown by metalorganic chemical vapor deposition

M. K. Lee, R. H. Horng, and L. C. Haung

Appl. Phys. Lett. 59, 3261 (1991); http://dx.doi.org/10.1063/1.105751 (3 pages) | Cited 17 times

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The relationship between electrical characteristics and structural ordering in undoped and Zn‐doped Ga0.5In0.5P films grown by metalorganic chemical vapor deposition is investigated. The Schottky diode was used to examine the electrical properties of the undoped samples with ordered and disordered structures. With the same carrier concentration (∼1.5×1016 cm−3), the diode fabricated on the ordered film shows a degraded current‐voltage characteristic. As the carrier concentration of Zn‐doped Ga0.5In0.5P increases above 1.5×1018 cm−3, the energy gap of the ordered structure is larger than that of the disordered structure. It was found that the hole mobility of the ordered film is lower than that of the disordered film with the similar doping level. The behavior could be attributed to the existence of antiphase boundaries within the ordered structure. The antiphase boundaries can act as recombination centers and/or scattering centers and result in the extraordinary electrical properties of the ordered samples.
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71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds
73.61.Ey III-V semiconductors
71.55.Jv Disordered structures; amorphous and glassy solids
68.55.-a Thin film structure and morphology

Intense photoluminescence from laterally anodized porous Si

K. H. Jung, S. Shih, T. Y. Hsieh, D. L. Kwong, and T. L. Lin

Appl. Phys. Lett. 59, 3264 (1991); http://dx.doi.org/10.1063/1.105752 (3 pages) | Cited 40 times

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We have studied photoluminescence (PL) from porous Si anodized laterally along the length of the Si wafer. Broad PL peaks were observed with peak intensities at ∼640 to 720 nm. Strong PL intensity could be observed from 550 to 860 nm. Room‐temperature peak intensities were within an order of magnitude of peak intensities of AlGaAs/GaAs multi‐quantum wells taken at 4.2 K, and total intensities were comparable. A blue shift of peak intensities from ∼680 to 620 nm could be observed after thermal anneal at 500 °C in O2 and subsequent HF dip.
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78.66.-w Optical properties of specific thin films
78.55.Hx Other solid inorganic materials

Lattice site locations of excess arsenic atoms in gallium arsenide grown by low‐temperature molecular beam epitaxy

Kin Man Yu and Z. Liliental‐Weber

Appl. Phys. Lett. 59, 3267 (1991); http://dx.doi.org/10.1063/1.105726 (3 pages) | Cited 12 times

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The excess As atoms present in as‐grown GaAs buffer layers grown by molecular beam epitaxy at low substrate temperature (∼200 °C) was measured by particle induced x‐ray emission to be ∼4×1020 atoms/cm3. The lattice site location of these excess As atoms in the layer was studied by ion channeling methods. Our results strongly suggested that the excess As atoms are located in an interstitial position close to the substitutional As atoms with a projected displacement ∼0.3 Å into the 〈110〉 channel. These results are consistent with the 〈111〉 split interstitials model suggested from TEM results. After annealing at 600 °C these excess As atoms coalesce forming As precipitates.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.jd Vacancies
61.72.jj Interstitials
61.85.+p Channeling phenomena (blocking, energy loss, etc.)

Residual oxygen levels in AlGaAs/GaAs quantum‐well laser structures: Effects of Si and Be doping and substrate misorientation

Naresh Chand, A. S. Jordan, S. N. G. Chu, and M. Geva

Appl. Phys. Lett. 59, 3270 (1991); http://dx.doi.org/10.1063/1.105727 (3 pages) | Cited 11 times

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Oxygen forms nonradiative recombination centers in GaAs and AlGaAs, and is a common contaminant in AlGaAs, irrespective of the growth technique. We find that O tends to accumulate near the GaAs active region of an AlGaAs/GaAs quantum‐well laser prepared by molecular beam epitaxy. Moreover, the Be‐doped Al0.6Ga0.4As cladding layer has a higher O content than its Si‐doped counterpart. We present evidence that Si‐doping suppresses, and Be doping favors incorporation of O in AlGaAs. In undoped and Si‐doped AlGaAs, the incorporation of O is further reduced by tilting the (100) GaAs substrates towards 〈111〉A. We propose that Be forms stable Be‐O complexes in AlGaAs, and thus, there is virtually no desorption of incorporated O. But in Si‐doped AlGaAs, O content is reduced due to reaction between group III suboxides and Si, resulting in the formation and desorption of volatile SiO (g). The study suggests that Be doping should be avoided in the p‐side of the GRIN region of a laser structure.
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61.72.-y Defects and impurities in crystals; microstructure
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
72.80.Ey III-V and II-VI semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Raman intensity enhancement of the Si peak by CdS thin films

C. M. Dai, D. S. Chuu, and W. F. Hsieh

Appl. Phys. Lett. 59, 3273 (1991); http://dx.doi.org/10.1063/1.105728 (3 pages) | Cited 2 times

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A method, which utilizes interference enhanced Raman scattering and resonant Raman scattering techniques, is used to overcome the low efficiency of Raman methods to diagnose highly reflective materials. As applied to the p‐type Si wafer, the enhanced gain is up to nearly a factor of 80 at 4880 Å excitation. Because of the strong absorption of the scattered light, it is recommended that the suitable deposited thickness of CdS films should not be thicker than 700 Å.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.40.Tv Optical and dielectric properties related to treatment conditions
78.30.Fs III-V and II-VI semiconductors

Subpicosecond carrier lifetime in GaAs grown by molecular beam epitaxy at low temperatures

S. Gupta, M. Y. Frankel, J. A. Valdmanis, J. F. Whitaker, G. A. Mourou, F. W. Smith, and A. R. Calawa

Appl. Phys. Lett. 59, 3276 (1991); http://dx.doi.org/10.1063/1.105729 (3 pages) | Cited 165 times

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Epitaxial GaAs grown by molecular beam epitaxy (MBE) at low substrate temperatures is observed to have a significantly shorter carrier lifetime than GaAs grown at normal substrate temperatures. Using femtosecond time‐resolved‐reflectance techniques, a sub‐picosecond (<0.4 ps) carrier lifetime has been measured for GaAs grown by MBE at ∼200°C and annealed at 600 °C. With the same material as a photoconductive switch we have measured electrical pulses with a full‐width at half‐maximum of 0.6 ps using the technique of electro‐optic sampling. Good responsivity for a photoconductive switch is observed, corresponding to a mobility of the photoexcited carriers of ∼120–150 cm2/V s. GaAs grown by MBE at 200 °C and annealed at 600 °C is also semi‐insulating, which results in a low dark current in the switch application. The combination of fast recombination lifetime, high carrier mobility, and high resistivity makes this material ideal for a number of subpicosecond photoconductive applications.
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73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.61.Ey III-V semiconductors
73.50.Pz Photoconduction and photovoltaic effects
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