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8 Mar 1993

Volume 62, Issue 10, pp. 1035-1166

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Bragg gratings fabricated in monomode photosensitive optical fiber by UV exposure through a phase mask

K. O. Hill, B. Malo, F. Bilodeau, D. C. Johnson, and J. Albert

Appl. Phys. Lett. 62, 1035 (1993); http://dx.doi.org/10.1063/1.108786 (3 pages) | Cited 235 times

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A photolithographic method is described for fabricating refractive index Bragg gratings in photosensitive optical fiber by using a special phase mask grating made of silica glass. A KrF excimer laser beam (249 nm) at normal incidence is modulated spatially by the phase mask grating. The diffracted light, which forms a periodic, high‐contrast intensity pattern with half the phase mask grating pitch, photoimprints a refractive index modulation into the core of photosensitive fiber placed behind, in proximity, and parallel, to the mask; the phase mask grating striations are oriented normal to the fiber axis. This method of fabricating in‐fiber Bragg gratings is flexible, simple to use, results in reduced mechanical sensitivity of the grating writing apparatus and is functional even with low spatial and temporal coherence laser sources.
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42.81.-i Fiber optics
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Semiconductor lasers on Si substrates using the technology of bonding by atomic rearrangement

Y. H. Lo, R. Bhat, D. M. Hwang, C. Chua, and C.‐H. Lin

Appl. Phys. Lett. 62, 1038 (1993); http://dx.doi.org/10.1063/1.108787 (3 pages) | Cited 49 times

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We demonstrated InGaAs/GaAs strained quantum well lasers on silicon substrates. The epitaxial layers for lasers were first grown on a GaAs substrate and then bonded to a silicon substrate using the technology of bonding by atomic rearrangement. Covalently bonded III‐V/Si heterointerface was confirmed by the cross‐sectional transmission electron microscopy. The ridge waveguide lasers on Si substrates lasing at about 1 μm wavelength have a 12 mA threshold current and a 56% external quantum efficiency at room temperature, at pulsed condition. Both the threshold current and the external quantum efficiency are close to the values of lasers on GaAs substrates. The technology of bonding by atomic rearrangement will be useful for making optoelectronic integrated circuits on Si.
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42.55.Px Semiconductor lasers; laser diodes
42.82.Cr Fabrication techniques; lithography, pattern transfer
68.55.-a Thin film structure and morphology

Novel biphotonic holographic storage in a side‐chain liquid crystalline polyester

P. S. Ramanujam, S. Hvilsted, and F. Andruzzi

Appl. Phys. Lett. 62, 1041 (1993); http://dx.doi.org/10.1063/1.108788 (3 pages) | Cited 28 times

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We report novel biphotonic holographic storage of text and gratings on unoriented films of a side‐chain liquid crystalline polyester capable of high density storage and complete erasure. The holograms have a typical size of 1 mm. The recording utilizes unusual photochemistry involving azo dye molecules. We believe that this technique would have a great potential in the recording of thousands of holograms in a two‐dimensional plane, as for instance in text retrieval systems and in the fabrication of high density interconnects in optical neural networks.
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42.40.-i Holography
42.30.-d Imaging and optical processing
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.79.Kr Display devices, liquid-crystal devices

Phase contrast and amplitude pseudoheterodyne interference near field scanning optical microscopy

M. Vaez‐Iravani and R. Toledo‐Crow

Appl. Phys. Lett. 62, 1044 (1993); http://dx.doi.org/10.1063/1.108789 (3 pages) | Cited 20 times

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Pseudoheterodyne detection of sample light in near field optical microscopy is demonstrated in an actively stabilized Mach–Zehnder interferometer. This results in a significant signal enhancement. Three distinct imaging modalities are described, which are based on the various stabilization feedback parameters, and scan speeds. A number of images are presented, demonstrating both amplitude and phase contrast imaging modalities.
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07.60.Pb Conventional optical microscopes
07.60.Ly Interferometers
42.30.-d Imaging and optical processing

Time‐lens producing 1.9 ps optical pulses

A. A. Godil, B. A. Auld, and D. M. Bloom

Appl. Phys. Lett. 62, 1047 (1993); http://dx.doi.org/10.1063/1.108790 (3 pages) | Cited 23 times

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A resonant microwave optical phase modulator in LiNbO3 with multiple passes, based on an off‐axis path in a stable optical resonator, is demonstrated as a time‐lens. With 1 W of cw microwave power at 5.2 GHz, 45 ps pulses at 1.06 μm were temporally focused to 6.7 ps (FWHM). Increasing the drive power to 13 W, at 10% duty cycle, produced 1.9 ps pulses. The aperture of the time‐lens is about 31 ps. This is the first demonstration of a useful time‐lens.
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42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.Hp Optical processors, correlators, and modulators
42.60.Fc Modulation, tuning, and mode locking

Modeling the current to light characteristics of index‐guided vertical‐cavity surface‐emitting lasers

J. W. Scott, S. W. Corzine, D. B. Young, and L. A. Coldren

Appl. Phys. Lett. 62, 1050 (1993); http://dx.doi.org/10.1063/1.108791 (3 pages) | Cited 11 times

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While there have been many advances in the field, vertical‐cavity surface‐emitting laser performance has been limited by undefined thermal effects. A temperature dependent, physically based model has been developed which simulates the steady state output characteristics of index‐guided vertical‐cavity surface‐emitting lasers. The model has lead to the development of lasers with improved temperature stability and output power. Experimental devices have been fabricated which exhibit a minimum threshold current of 1.6 mA at 70 °C with a variation of less than 0.5 mA over a 80 °C range.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Colliding pulse mode locking of a semiconductor laser in an external ring cavity

C. F. Lin and C. L. Tang

Appl. Phys. Lett. 62, 1053 (1993); http://dx.doi.org/10.1063/1.108792 (3 pages) | Cited 2 times

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Colliding pulse mode locking of a semiconductor laser is achieved by monolithically integrating an absorber in the center of a laser diode structure with chemically assisted ion beam etched angled facets in an external ring cavity. Minimum deconvolved pulses as short as 1.6 ps before compression and near‐transform‐limited pulses of 0.35 ps after compression are measured.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Excimer laser ablated barium strontium titanate thin films for dynamic random access memory applications

D. Roy and S. B. Krupanidhi

Appl. Phys. Lett. 62, 1056 (1993); http://dx.doi.org/10.1063/1.108793 (3 pages) | Cited 78 times

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Polycrystalline thin films of Ba0.5Sr0.5TiO3 were deposited by excimer laser (248 nm) ablation. Films deposited near 575 °C exhibited good crystallinity, a dielectric constant of 330, a dissipation factor of 0.02, a leakage current density of 2×10−7 A/cm2, a charge storage density of 36 fC/μm2, and breakdown time of 3700 s at an applied electric field of 0.125 MV/cm. The C‐V (capacitance‐voltage) behavior of both MFM (metal‐ferroelectric‐metal) and MFS (metal‐ferroelectric‐semiconductor) structures were studied and the estimated dielectric permittivity in the accumulation region of MFS structure nearly indicated the bulk value, suggesting a reasonably good Ba0.5Sr0.5TiO3/Si interface.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Tunable guided‐wave optical polarization converters in lithium tantalate

Z. Tang, O. Eknoyan, H. F. Taylor, and V. P. Swenson

Appl. Phys. Lett. 62, 1059 (1993); http://dx.doi.org/10.1063/1.108794 (3 pages) | Cited 6 times

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Tunable guided‐wave TE↔TM mode converters have been produced in LiTaO3 using strain‐induced polarization mode coupling. The waveguides are formed by Zn diffusion from the vapor phase. Phase matched coupling is obtained by depositing a thick SiO2 film at an elevated temperature and delineating a spatially periodic pattern in the film at room temperature. The static shear strain resulting from the large thermal expansion mismatch between the substrate and film causes an off‐diagonal change in the refractive index via the strain‐optic effect and promotes TE↔TM coupling. Polarization conversion in excess of 98% was achieved at a wavelength of 627 nm in X‐cut LiTaO3. The conversion efficiency is highly wavelength selective, with a spectral width of 7.3 nm in the 5.4 mm long device. Thermal and electro‐optic tuning of the center wavelength was demonstrated.
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42.79.-e Optical elements, devices, and systems
42.79.Gn Optical waveguides and couplers

High‐power buried InGaAsP/GaAs (λ=0.8 μm) laser diodes

D. Z. Garbuzov, N. Ju. Antonishkis, S. N. Zhigulin, N. D. Il’inskaya, A. V. Kochergin, D. A. Lifshitz, E. U. Rafailov, and M. V. Fuksman

Appl. Phys. Lett. 62, 1062 (1993); http://dx.doi.org/10.1063/1.108795 (3 pages) | Cited 9 times

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Buried InGaAsP/GaAs (λ=0.78 μm) separate confinement‐single quantum well laser diodes have been prepared and studied for the first time. It has been shown that a stable far field pattern can be observed even at 500 mW continuous wave (cw) output power for diodes with active region width of about 7 μm, and single zero‐mode operation has been obtained up to 170 mW cw for diodes with a width of 3.8 μm. Mirror facet overheating for the diodes studied was an order of magnitude less than that for similar AlGaAs/GaAs diodes.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation

Liquid crystal millimeter wave electronic phase shifter

K. C. Lim, J. D. Margerum, and A. M. Lackner

Appl. Phys. Lett. 62, 1065 (1993); http://dx.doi.org/10.1063/1.108796 (3 pages) | Cited 38 times

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The birefringence of two common nematic liquid crystals were measured in the millimeter wave range, and were found to be in the range of 0.19–0.22 at room temperature. Using liquid crystal electro‐ and magneto‐optical effects, we present the first experimental data of a novel liquid crystal millimeter wave electronic phase shifter. Our experiments show that liquid crystals could play an important role in future millimeter wave device technologies.
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84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors
84.40.-x Radiowave and microwave (including millimeter wave) technology
61.30.-v Liquid crystals

Efficient coupling of high‐intensity subpicosecond laser pulses into solids

M. M. Murnane, H. C. Kapteyn, S. P. Gordon, J. Bokor, E. N. Glytsis, and R. W. Falcone

Appl. Phys. Lett. 62, 1068 (1993); http://dx.doi.org/10.1063/1.108797 (3 pages) | Cited 68 times

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We demonstrate a new technique for enhancing the absorption of high‐intensity, ultrashort‐duration laser pulses by solids. Targets consisting of gold gratings and gold clusters were found to absorb greater than 90% of the incident high‐intensity laser light. This is in contrast to less than 10% absorption by flat surfaces. As a result of this strong coupling of the laser to a high‐density plasma, conversion efficiency of laser energy to x rays of greater than 1% was observed for x rays above 1 keV. Efficiency of nearly 25% was observed for emissions greater than 30 eV. These conversion efficiencies are more than an order of magnitude greater than those measured from flat targets.  
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.38.-r Laser-plasma interactions
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
79.20.Ds Laser-beam impact phenomena

Two‐photon pumped blue lasing in bulk ZnSe and ZnSSe

X. H. Yang, J. M. Hays, W. Shan, J. J. Song, and E. Cantwell

Appl. Phys. Lett. 62, 1071 (1993); http://dx.doi.org/10.1063/1.108798 (3 pages) | Cited 21 times

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We have studied laser action of ZnSe and ZnS0.05Se0.95 samples grown by seeded physical vapor phase transport (SPVT) technique in the near resonant two‐photon absorption regime. The two‐photon pumped lasing was observed using a tunable near‐infrared nanosecond laser (830–890 nm). Blue lasing could be observed up to 200 K and the two‐photon pumped lasing threshold was measured to be ∼7 MW/cm2 at 10 K. This work demonstrates the applicability of using near‐infrared diode lasers as pumping sources to excite the ZnSe‐based materials. By comparing the energy position of two‐photon pumped lasing with that of the one‐photon pumped lasing and examining the red shift of the energy position, we suggest that the free‐exciton free‐exciton scattering and resultant band filling are the dominant processes involved in the lasing action of ZnSe and ZnSSe alloy crystals at low temperature.
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42.55.Px Semiconductor lasers; laser diodes
78.45.+h Stimulated emission

Scanning tunneling microscopy studies of vapor deposited films of tetrathiafulvalene with iodine

J. J. Breen, J. S. Tolman, and G. W. Flynn

Appl. Phys. Lett. 62, 1074 (1993); http://dx.doi.org/10.1063/1.108799 (3 pages) | Cited 2 times

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Scanning tunneling microscopy studies are reported for vacuum deposited conducting films of tetrathiafulvalene (TTF) with iodine (I) codeposited on mica substrates. Molecular resolution images reveal a crystal structure consistent with that of single crystals of a material with chemical composition (TTF)7I5 with the crystal c axis parallel to the plane of the mica substrate. The imaged surface is terminated with TTF molecules, and the submicron dimension crystal planes which are observed reveal surface steps consistent with the layered and stacked nature characteristic of charge transfer salt materials.
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68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Real time electron microscopy inspection of high temperature processes in W free standing wires

J. Gómez‐Herrero, J. I. Pascual, J. Méndez, and A. M. Baró

Appl. Phys. Lett. 62, 1077 (1993); http://dx.doi.org/10.1063/1.108800 (2 pages) | Cited 3 times

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High temperature structural changes in a W wire are studied in situ by scanning electron microscopy. This is made possible by the microscopic size of the wire. Grain‐boundary grooving and faceting are observed in real time. The constriction exhibits a strong thermal gradient (∼100 K μm−1) which is the driving force for the migration mechanisms responsible for the observed phenomena.
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66.30.Fq Self-diffusion in metals, semimetals, and alloys
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Simulation of three‐dimensional director structures in twisted nematic liquid crystal displays

A. Lien

Appl. Phys. Lett. 62, 1079 (1993); http://dx.doi.org/10.1063/1.108801 (3 pages) | Cited 16 times

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The three‐dimensional simulation of the liquid crystal director deformation profile and the electric field distribution for the twisted nematic liquid crystal display has been carried out for the first time. The result gives us a complete understanding about liquid crystal deformation profile inside a pixel and the locus of the disclination line pair across the entire pixel area. This would not be possible in the case of the two‐dimensional (2D) simulation [A. Lien, Proceedings of the 10th International Display Research Conference (vde‐verlag gmbh, Berlin und Offenbach, 1990), p. 248; G. Haas, H. Wohler, M. W. Fritsch, and D. A. Mlynski, ibid., p. 252; A. Lien and R. A. John, IBM J. Res. Devel. 36, 51 (1992)], since the 2D simulation result is accurate only for the region which is far away from the corner area of a pixel.
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61.30.-v Liquid crystals
42.79.Kr Display devices, liquid-crystal devices

Demonstration of a new tool for degradation of amorphous hydrogenated silicon and the importance of the Fermi level shift

J. Kočka, O. Štika, and O. Klíma

Appl. Phys. Lett. 62, 1082 (1993); http://dx.doi.org/10.1063/1.109602 (3 pages) | Cited 4 times

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We introduce the pulsed Ruby laser as a new efficient degradation tool for amorphous hydrogenated silicon (a‐Si:H). We present the degradation dynamics and the saturated values of the density of states (DOS) and the room temperature conductivity. Comparison of two samples with different impurity content indicates the impurity‐related initial Fermi level shift. By a simple model we illustrate the influence of this shift on the initial stage of degradation (its acceleration or delay) and consequently, also on the saturated DOS.
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73.61.Jc Amorphous semiconductors; glasses
72.80.Ng Disordered solids
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Transmission of phonons through grain boundaries in diamond films

D. T. Morelli, C. Uher, and C. J. Robinson

Appl. Phys. Lett. 62, 1085 (1993); http://dx.doi.org/10.1063/1.108802 (3 pages) | Cited 24 times

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The influence of grain boundary scattering of lattice waves in high quality diamond films has been determined by the measurement of thermal conductivity down to 0.15 K. We find that the mean free path for lattice vibrations (phonons) exceeds substantially the crystallite size and approaches the physical size of the sample. This implies that a significant transmission of phonons occurs between the grains of these polycrystalline diamond materials.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
63.20.kp Phonon-defect interactions
61.72.Mm Grain and twin boundaries

Simultaneous occurrence of multiphases in the interfacial reactions of ultrahigh vacuum deposited Hf and Cr thin films on (111)Si

W. Y. Hsieh, J. H. Lin, and L. J. Chen

Appl. Phys. Lett. 62, 1088 (1993); http://dx.doi.org/10.1063/1.108803 (3 pages) | Cited 14 times

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Simultaneous occurrence of multiphases were observed in the interfacial reactions of ultrahigh vacuum deposited Hf and Cr thin films on (111)Si by high‐resolution transmission electron microscopy in conjunction with fast Fourier transform diffraction analysis and image simulation. For Hf/Si system, an amorphous interlayer, Hf5Si3 as well as FeB and CrB types of HfSi were found to form simultaneously in samples annealed at 530 °C for 40–80 min. For Cr/Si system, an amorphous interlayer, Cr5Si3, CrSi, and CrSi2 were observed to form in samples annealed at 375 °C for 30 min. The formation of multiphases appeared to be quite general in the initial stages of interfacial reactions of ultrahigh vacuum deposited refractory thin films. The results called for a reexamination of generally accepted ‘‘difference’’ in reaction sequence between bulk and thin‐film couples.
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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
68.35.Dv Composition, segregation; defects and impurities

Electric‐field‐induced phase changes in polyvinylidene fluoride: Effects from corona polarity and moisture

Mauro M. Costa and José A. Giacometti

Appl. Phys. Lett. 62, 1091 (1993); http://dx.doi.org/10.1063/1.108804 (3 pages) | Cited 2 times

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The constant‐current corona triode has been used to charge and monitor the surface potential buildup of polyvinylidene fluoride samples in α form. Under dry air and positive polarity it is possible to pole the samples to sufficiently high electric fields so as to cause a phase change from the nonpolar to the polar δ form. This phase transition is confirmed by x‐ray diffractograms. Surface potential measurements on δ samples display a ferroelectric behavior in which a plateau appears in the surface potential buildup curve due to the dipole reorientation. The values of the remanent polarization and the coercive field were estimated to be ∼50 mC/m2 and ∼65 MV/m, respectively.
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61.41.+e Polymers, elastomers, and plastics
77.22.Ej Polarization and depolarization
77.80.B- Phase transitions and Curie point
77.84.Jd Polymers; organic compounds

Geometrical shape dependent polarization anisotropy in electroluminescence from InGaAs/InP quantum wires

M. Notomi, M. Okamoto, H. Iwamura, and T. Tamamura

Appl. Phys. Lett. 62, 1094 (1993); http://dx.doi.org/10.1063/1.108752 (3 pages) | Cited 15 times

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The polarization properties of edge‐emitted electroluminescence from InGaAs/InP quantum wires fabricated by reverse‐mesa wet etching, electron‐beam lithography, and overgrowth, are investigated. Strongly TE polarized electroluminescence from relatively wide wires approaches isotropy as the wires become narrower. The observed dependence on wire size is attributed to a transition from a two‐dimensional to a one‐dimensional system. The implication is that quantum wires could potentially be applied to polarization‐controlled devices, such as polarization insensitive optical amplifiers.
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78.60.Fi Electroluminescence
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Large blue shift of light emitting porous silicon by boiling water treatment

X. Y. Hou, G. Shi, W. Wang, F. L. Zhang, P. H. Hao, D. M. Huang, and X. Wang

Appl. Phys. Lett. 62, 1097 (1993); http://dx.doi.org/10.1063/1.108753 (2 pages) | Cited 42 times

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A boiling water treatment of light emitting porous silicon can give rise to a large blue shift of its photoluminescence spectrum and meanwhile strengthen the skeleton of porous Si by filling up many pores with aqueous oxide. A stable blue‐green light emission at the peak wavelength down to 500 nm is achieved. FTIR measurements show that the formation of Si dihydride on the sidewall surfaces of the Si rods is not responsible to the visible luminescence for the very thin Si wires.
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78.55.Hx Other solid inorganic materials
78.30.Hv Other nonmetallic inorganics
81.65.-b Surface treatments

Role of Si‐H and Si‐H2 in the photoluminescence of porous Si

J. M. Lavine, S. P. Sawan, Y. T. Shieh, and A. J. Bellezza

Appl. Phys. Lett. 62, 1099 (1993); http://dx.doi.org/10.1063/1.108754 (3 pages) | Cited 40 times

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FTIR spectra reported by Brandt et al. [Solid State Commun. 81, 307 (1992)], Tischler et al. [Appl. Phys. Lett. 60, 639 (1992)], and Tsai et al. [Appl. Phys. Lett. 59, 2814 (1991), and 60, 1700 (1992)] have shown the presence of Si‐H and Si‐H2 lines in porous Si which Canham [Appl. Phys. Lett. 57, 1046 (1990)], Tischler and Tsai have considered essential to the observation of visible photoluminescence (PL). Hydrogen has been ascribed as a surface passivating agent which eliminates nonradiative transitions thus enabling PL to occur. Photo‐oxidation has been described as replacing some of the surface passivants with oxygen, generating nonradiative transitions which quench the PL. We have markedly reduced the Si‐H and Si‐H2 content of anodized samples by treatment with CCl4 vapor. Comparison of the photoluminescent emission and excitation spectra for CCl4 treated and untreated samples show very similar results. Comparison of the FTIR spectra of photo‐oxidized samples which exhibit no PL and as‐anodized samples show the similar presence of Si‐H and Si‐H2. These observations suggest that neither Si‐H nor Si‐H2 is essential for the observation of PL in anodized Si. This result and the similarity in the behavior of porous Si with the polysilynes lead us to concur with Brandt et al. that visible PL in anodized Si is generated by the backbone of a 2D Si polymer.  
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78.55.Hx Other solid inorganic materials

Semi‐insulating crystalline silicon formed by oxygen doping during low‐temperature chemical vapor deposition

P. V. Schwartz, C. W. Liu, and J. C. Sturm

Appl. Phys. Lett. 62, 1102 (1993); http://dx.doi.org/10.1063/1.108755 (3 pages)

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In this letter we demonstrate the use of oxygen as a dopant in silicon to create semi‐insulating, crystalline silicon films grown by chemical vapor deposition. The films contain oxygen concentrations that exceed the peak solid solubility of oxygen in silicon by several orders of magnitude, yet they remain crystalline. The resistivities of these films reach levels of 106 Ω cm at room temperature and the electronic properties of the films exhibit classical characteristics of space‐charge‐limited current associated with insulators containing trap states within the band gap. We then demonstrate that metal‐oxide‐semiconductor transistors with bulk‐like mobilities can be fabricated in crystalline silicon layers grown without oxygen on top of the semi‐insulating films.
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68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.40.Ty Semiconductor-insulator-semiconductor structures

Modulation‐doped In0.48Al0.52P/In0.2Ga0.8As field‐effect transistors

Jenn‐Ming Kuo, Yi‐Jen Chan, and Dimitris Pavlidis

Appl. Phys. Lett. 62, 1105 (1993); http://dx.doi.org/10.1063/1.108756 (3 pages) | Cited 9 times

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In0.48Al0.52P/In0.2Ga0.8As pseudomorphic modulation‐doped field‐effect transistors (MODFETs) were realized for the first time by gas‐source molecular beam epitaxy on GaAs substrates. Extrinsic transconductances of 173 and 283 mS/mm at 300 and 77 K, respectively, were measured for MODFETs with a 1 μm long and 75 μm wide gate. The devices showed very good pinch‐off characteristics, and the output conductance was only 1.3 mS/mm. Extremely high Schottky barrier height (0.92 eV) and low gate leakage current (Irev<250 nA at VGS=−5 V) were achieved. The gate breakdown voltage was −17 V. No I‐V collapse was observed at 77 K. Microwave measurements showed that the current gain cutoff frequency fT of the devices was 11.5 GHz and the maximum frequency of oscillation fmax, was 26 GHz. These results demonstrate the promising potential of pseudomorphic In0.48Al0.52P/InGaAs MODFETs as high frequency and high power devices.
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85.30.Tv Field effect devices
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
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