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29 Jul 1996

Volume 69, Issue 5, pp. 593-713

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Controlling filamentation in broad‐area semiconductor lasers and amplifiers

John R. Marciante and Govind P. Agrawal

Appl. Phys. Lett. 69, 593 (1996); http://dx.doi.org/10.1063/1.117917 (3 pages) | Cited 5 times

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We show that with the introduction of a new pair of epitaxial layers, sandwiched between the active and cladding regions, self‐defocusing can play an important role in stabilizing the lateral mode in broad‐area semiconductor lasers and amplifiers. Under certain conditions, it can be used to eliminate filamentation and provide a nearly flat mode profile by adjusting the band gap of the new self‐defocusing layers. We discuss the use of a strained multiple‐quantum‐well laser for producing such a stable lateral mode. © 1996 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Mi Dynamical laser instabilities; noisy laser behavior
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Visible electroluminescence from nanocrystallites of silicon films prepared by plasma enhanced chemical vapor deposition

Song Tong, Xiang‐na Liu, Lu‐chun Wang, Feng Yan, and Xi‐mao Bao

Appl. Phys. Lett. 69, 596 (1996); http://dx.doi.org/10.1063/1.117918 (3 pages) | Cited 13 times

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We have observed visible electroluminescence (EL) from silicon nanocrystallites which are embedded in a‐Si:H films prepared in a plasma enhanced chemical vapor deposition system. The EL spectra are in the range of 500–850 nm with two peaks located at about 630–680 and 730 nm, respectively. We found that the intensity of EL peaks is related closely to the conductivity of the deposited films. The carrier conduction path is discussed in terms of the material structural characteristics, and a tentative explanation of the light emission mechanism is proposed. © 1996 American Institute of Physics.
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78.60.Fi Electroluminescence
78.66.Jg Amorphous semiconductors; glasses
78.66.Db Elemental semiconductors and insulators

Enhanced quantum efficiency in polymer electroluminescence devices by inserting a tunneling barrier formed by Langmuir–Blodgett films

Young‐Eun Kim, Heuk Park, and Jang‐Joo Kim

Appl. Phys. Lett. 69, 599 (1996); http://dx.doi.org/10.1063/1.117919 (3 pages) | Cited 101 times

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Quantum efficiency in a polymer electroluminescence device is significantly improved by inserting a thin insulating layer with the thickness of tunneling range. Four times higher quantum efficiency was obtained without the increase of the threshold voltage. Poly(methyl methacrylate) Langmuir–Blodgett films were used as the thin tunneling barrier. The enhancement may result from the lowering of the effective barrier height for electron injection while increasing the effective barrier for hole injection. The effects improve the balanced injection of electrons and holes into the light‐emitting devices. © 1996 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
42.70.Jk Polymers and organics

Reduction of structural defects in II–VI blue green laser diodes

C. C. Chu, T. B. Ng, J. Han, G. C. Hua, R. L. Gunshor, E. Ho, E. L. Warlick, L. A. Kolodziejski, and A. V. Nurmikko

Appl. Phys. Lett. 69, 602 (1996); http://dx.doi.org/10.1063/1.117920 (3 pages) | Cited 18 times

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Early blue/green laser diodes based on ZnSe exhibited room temperature, continuous wave (cw) lifetimes of the order of a minute. Similar to the history of (Al,Ga)As lasers, the source of the degradation was the presence of extended crystalline defects. The dominant extended defects in the early room temperature cw lasers originated as stacking faults generated at the ZnSe/GaAs heterovalent nucleation event, and exhibited densities of the order of 106 cm−2. In this letter, a procedure is described which will ensure a consistent run to run reduction of the density of such extended defects to the mid to low 103 cm−2 over a 3 in. wafer. © 1996 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
61.72.Nn Stacking faults and other planar or extended defects
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

p‐i‐n‐i‐p photodetector proposal and integration with waveguides

A. Bruno, F. Huet, M. Carre, M. Foucher, M. Billard, F. Devaux, J. Brandon, L. Menigaux, A. Carenco, and A. Scavennec

Appl. Phys. Lett. 69, 605 (1996); http://dx.doi.org/10.1063/1.117921 (3 pages)

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We propose a photodiode configuration suited for waveguide integration, and top and side illumination. This configuration based on a pair of p‐i‐n photodiodes, laid out alongside of one another, requires only one metallization type, and therefore, reduces the number of technological steps. A waveguide–photodiode integration illustrates this photodetector concept. The single heterostructure waveguide integrated evanescently with this p‐i‐n‐i‐p photodetector exhibits a 19 GHz bandwidth, as a result of the very low (30 fF) capacitance of a 20 μm long detector. Related to its symmetrical features, this p‐i‐n‐i‐p photodetector is a means to improve fabrication yield of integrated optoelectronic devices. © 1996 American Institute of Physics.
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42.82.Bq Design and performance testing of integrated-optical systems
85.60.Gz Photodetectors (including infrared and CCD detectors)

Microcavity devices based on a ladder‐type poly(p‐phenylene) emitting blue, green, and red light

Vera Cimrová, Ulrich Scherf, and Dieter Neher

Appl. Phys. Lett. 69, 608 (1996); http://dx.doi.org/10.1063/1.117922 (3 pages) | Cited 24 times

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Light emitting devices with emission either in the blue, green, and red spectral region have been fabricated based on ladder‐type poly(p‐phenylene) (LPPP). Color tuning has been achieved simply by adjusting the LPPP layer thickness. Microcavity effects could be proven to control the shape of the electroluminescence and photoluminescence spectra of the single layer devices between aluminum and gold electrodes. The full width at half‐maximum was strongly reduced from ∼150 to 200 nm for the ‘‘free space’’ photoluminescence or for the electroluminescence spectra of devices with indium–tin oxide hole injecting electrodes to values between 60 and 70 nm for the three individual single color devices. © 1996 American Institute of Physics.
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85.60.Jb Light-emitting devices
42.70.Jk Polymers and organics
78.60.Fi Electroluminescence

Theory and properties of quasiwaveguide modes

Huitian Wang, Tadashi Aruga, and Peixian Ye

Appl. Phys. Lett. 69, 611 (1996); http://dx.doi.org/10.1063/1.117923 (3 pages) | Cited 2 times

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A theory is developed to explain the origin of physical phenomena in quasiwaveguide, based on the forward scattering and multiple‐wave interference effects. The properties of quasiwaveguide modes, such as positions, linewidths, the reflectivity of the reflected light spot, and the reflectivity distribution of scattered light are described. The shape of the m‐lines is derived theoretically. Applications of the theory are also discussed. © 1996 American Institute of Physics.
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42.25.-p Wave optics
42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers

A nonlinear interaction of two acoustic beams on the solid interface

X. He, Y. Shui, Y. Mao, and W. Jiang

Appl. Phys. Lett. 69, 614 (1996); http://dx.doi.org/10.1063/1.117924 (3 pages)

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Two incident ultrasonic shear wave beams of 7.5 MHz interact at glass‐metal interface, and the reflected longitudinal wave of 15 MHz normal to the interface are investigated. This effect is identified as a nonlinear interface effect and the sum frequency signal is the convolution of two input signals. The convolution efficiency is measured as about 106 dBm for glass‐iron interface. The observation reveals that the quality of interface bonding has a significant influence on the convolution output. So the nonlinear effect is found to be useful for implementation of convolution or nondestructive evaluation of bonding layer. Theoretical analysis and experimental measurements on the effect are presented in this letter. © 1996 American Institute of Physics.
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43.25.Dc Nonlinear acoustics of solids
43.25.Jh Reflection, refraction, interference, scattering, and diffraction of intense sound waves
43.35.Zc Use of ultrasonics in nondestructive testing, industrial processes, and industrial products

Efficient production of O+ and O− ions in a helicon wave oxygen discharge

T. Mieno, T. Kamo, D. Hayashi, T. Shoji, and K. Kadota

Appl. Phys. Lett. 69, 617 (1996); http://dx.doi.org/10.1063/1.117925 (3 pages) | Cited 12 times

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High density oxygen plasmas (ne=1010–1013 cm−3) are produced by a helicon wave discharge source with rf powers of 0.1–3 kW. Positive and negative ion species in the plasmas are measured by a time‐of‐flight mass spectrometer. The intensity ratio of O+ to O+2 increases with the electron density ne and is almost proportional to it in the region of ne=1010–1012 cm−3. When the electron density increases up to 8×1012 cm−3, the ratio becomes about 4. In a high density plasma of 1.3×1013 cm−3 obtained by mixing Ar gas, about 83% of the positive oxygen ions becomes O+. By using pulse modulation of the rf power, O− ions are mainly observed with remarkable increase in the afterglow. The maximum density of O− is about 3×1011 cm−3 at 30 μs after turning off the rf power of 0.85 kW and the decay time of O− is about 60 μs. © 1996 American Institute of Physics.
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52.50.Dg Plasma sources
52.70.Nc Particle measurements
52.80.Pi High-frequency and RF discharges

Whiskerlike structure growth on silicon exposed to ArF excimer laser irradiation

F. Sánchez, J. L. Morenza, R. Aguiar, J. C. Delgado, and M. Varela

Appl. Phys. Lett. 69, 620 (1996); http://dx.doi.org/10.1063/1.117926 (3 pages) | Cited 26 times

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The effects of ArF excimer laser irradiation on silicon single crystals in air have been studied. The etch rate versus fluence curve shows three well defined zones, with very different etch rates and dependences. In the intermediate zone (from 1.5 to 2.5 J/cm2), narrow (1–2 μm diameter) and tall columns (3–30 μm) start to grow after irradiation with some hundreds of laser pulses. These whiskerlike columns, with height between one and two orders of magnitude higher than the depth of the crater, have not been formed by preferential etching of the surrounding material, but through hydrodynamical processes. © 1996 American Institute of Physics.
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68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors

Response mechanism of nematic liquid crystals using the in‐plane switching mode

Masahito Oh‐e and Katsumi Kondo

Appl. Phys. Lett. 69, 623 (1996); http://dx.doi.org/10.1063/1.117927 (3 pages) | Cited 49 times

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See Also: Erratum

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A response mechanism of nematic liquid crystals following the switching‐on and off of an in‐plane electric field when using the in‐plane switching (IPS) mode was investigated. Simplified theoretical expressions, which were derived with an assumption that an in‐plane electric field was applied to the liquid crystals, were used to explain the dynamical switching process in the IPS mode. In particular, the relaxation time of the liquid crystals when removing the electric field was described as a proportional relationship to the square of the cell gap. A thinner cell gap also proved to be effective in obtaining a fast response time in the IPS mode. By contrast, the switching‐on time when applying the in‐plane electric field proved to be inversely proportional to the difference between the square of the electric field strength and the square of the critical electric field strength at which the liquid crystals begin to deform. © 1996 American Institute of Physics.
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61.30.-v Liquid crystals
42.70.Df Liquid crystals
78.20.Jq Electro-optical effects

Electric field domains in intentionally perturbed semiconductor superlattices

G. Schwarz, F. Prengel, E. Schöll, J. Kastrup, H. T. Grahn, and R. Hey

Appl. Phys. Lett. 69, 626 (1996); http://dx.doi.org/10.1063/1.117928 (3 pages) | Cited 10 times

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Simulations based on a rate equation model for high‐field transport through a doped semiconductor superlattice are presented for the case that one barrier is chosen significantly wider than the others. The distinct impact of that local perturbation on the overall shape of the current–voltage characteristic is discussed and related to the spatial field distribution. The measured current–voltage characteristic of a superlattice, which was intentionally grown with one thicker barrier, confirms the strong asymmetry predicted by the model calculations. © 1996 American Institute of Physics.
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73.50.Fq High-field and nonlinear effects
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.61.Ey III-V semiconductors

Phase time for coherent transport in two‐dimensional structures

Antonio Abramo, Paolo Casarini, and Carlo Jacoboni

Appl. Phys. Lett. 69, 629 (1996); http://dx.doi.org/10.1063/1.117929 (3 pages)

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In this letter the expression of the phase time is derived for a two‐dimensional coherent wave packet traveling through a generic mesoscopic system. The obtained analytical expression generalizes the definition of phase time for a single one‐dimensional scattering state to the case of coherent transport through two‐dimensional multichannel mesoscopic structures, and results in a suitable average of the single‐mode phase times. As an application, numerical results for a quantum wire and a double‐barrier resonant‐tunneling diode with and without an ionized impurity are also presented. © 1996 American Institute of Physics.
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73.23.-b Electronic transport in mesoscopic systems
72.15.Rn Localization effects (Anderson or weak localization)
73.40.Gk Tunneling

Effects of the external electric field from a substrate on Cl2 gas adsorption on SnO2 thin films

Yoshiko Niki Kunishima, Masaru Miyayama, and Hiroaki Yanagida

Appl. Phys. Lett. 69, 632 (1996); http://dx.doi.org/10.1063/1.117930 (3 pages) | Cited 4 times

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Changes in current by Cl2 gas adsorption were measured at 200 °C for SnO2 films sputtered on SiO2/Si substrates, with a varying electric field from the substrate. Properties of Cl2 adsorption, such as sensitivity and reaction rate constant, under a positive (+5 V) substrate bias were almost the same with those under 0 V bias. However, under a negative (−5 V) substrate bias, the current decreased remarkably by Cl2 adsorption and a high sensitivity was obtained. Moreover, the reaction rate constant was found to be about 10 times or more larger than those under 0 V and +5 V with positive biases. It was indicated that an external electric field affects the adsorption behavior of Cl2 on SnO2 surface. © 1996 American Institute of Physics.
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68.43.-h Chemisorption/physisorption: adsorbates on surfaces
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
73.61.Le Other inorganic semiconductors

Efficient carrier blocking by an attractive potential in strained Si1−xGex/Si single quantum well

Y. Kishimoto, Y. Shiraki, and S. Fukatsu

Appl. Phys. Lett. 69, 635 (1996); http://dx.doi.org/10.1063/1.117931 (3 pages) | Cited 2 times

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Efficient carrier blocking by a single ‘‘attractive’’ potential is demonstrated using a strained Si0.85Ge0.15/Si quantum well (QW). The carrier blocking becomes pronounced at increased temperatures as most of the carriers at the QW bound state are thermalized with the barrier band edge. The carrier blocking efficiency at 100 K is almost of the order of unity as compared to insufficient carrier blocking due to a large ‘‘repulsive’’ potential associated with SiO2. The carrier blocking arises from efficient hole reemission from the QW that reflects a highly efficient carrier capture to the strained Si1−xGex/Si QWs from Si barriers. It is further shown that a single QW is the optimized geometry for efficient carrier blocking and that multiple well potentials lead only to a reduced blocking efficiency. © 1996 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Le Other inorganic semiconductors

Nanostructure fabrication using the selective thermal desorption of SiO2 induced by electron beams

S. Fujita, S. Maruno, H. Watanabe, and M. Ichikawa

Appl. Phys. Lett. 69, 638 (1996); http://dx.doi.org/10.1063/1.117932 (3 pages) | Cited 36 times

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It has been found that selective thermal desorption of SiO2 on Si (111) substrate is induced by electron‐beam irradiation. By using this selective thermal desorption, a nanofabrication technique has been realized by focused electron beams. Open windows of 10 nm width in a SiO2 film have been fabricated by this technique. A pattern transfer from the open windows to thin Si films has also been performed by Si growth and subsequent heating. This has produced Si wires of 10 nm width. © 1996 American Institute of Physics.
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79.20.La Photon- and electron-stimulated desorption
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
81.65.Cf Surface cleaning, etching, patterning

Improvement of AlGaAs/AlGaAs interface by in situ low‐temperature H2 annealing in metalorganic vapor phase epitaxial regrowth

S. Gotoh and H. Horikawa

Appl. Phys. Lett. 69, 641 (1996); http://dx.doi.org/10.1063/1.117791 (3 pages) | Cited 2 times

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A new type of thermal treatment for air‐exposed AlGaAs surfaces, in situ low‐temperature H2 annealing, has been developed regrowing AlGaAs in metalorganic vapor phase epitaxy. The quality of regrown interface was evaluated by photoluminescence (PL) spectrum from Al0.3Ga0.7As/GaAs/Al 0.3Ga0.7As quantum wells near the interface of the initial AlGaAs layer. Remarkable recovery of PL intensity was observed by this newly developed process, indicating that initial air‐exposed AlGaAs surface states are reduced. © 1996 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.35.Fx Diffusion; interface formation
78.66.Fd III-V semiconductors

Determination of slant angle of p–n interface by multiwavelength near‐field photocurrent measurement

T. Saiki, N. Saito, J. Kusano, and M. Ohtsu

Appl. Phys. Lett. 69, 644 (1996); http://dx.doi.org/10.1063/1.117792 (3 pages) | Cited 3 times

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Near‐field photocurrent measurements with multiwavelength excitation sources are applied to the investigation of a lateral p–n junction grown on patterned GaAs (111)A substrate. In order to probe the internal properties of this device, propagation modes into the sample are utilized retaining high resolution with the contribution of a penetration depth smaller than the aperture diameter. By systematically varying the penetration depth over a wide range up to 900 nm, photocurrent signals due to internal optical response clearly appear. The capability of ‘‘tomographic’’ diagnostics is demonstrated and the slant angle of the p–n interface is determined to be 30±8°. © 1996 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Pz Photoconduction and photovoltaic effects

High quality CuInSe2 films grown on pseudo‐lattice‐matched substrates by molecular beam epitaxy

S. Niki, P. J. Fons, A. Yamada, T. Kurafuji, S. Chichibu, H. Nakanishi, W. G. Bi, and C. W. Tu

Appl. Phys. Lett. 69, 647 (1996); http://dx.doi.org/10.1063/1.117793 (3 pages) | Cited 20 times

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CuInSe2 films have been grown by molecular beam epitaxy on pseudo‐lattice‐matched substrates that consist of a 1‐μm‐thick In0.29Ga0.71As layer grown on a linearly composition‐graded InxGa1−xAs buffer (0≤x≤0.29) grown in turn on GaAs (001). The properties of these films have been compared with those of the films grown directly on GaAs (001). High resolution x‐ray diffraction analysis on CuInSe2 grown on pseudo‐lattice‐matched substrates indicated substantial reduction on residual strain in the CuInSe2 films. A photoluminescence spectrum dominated by sharp free exciton emissions has been observed for the first time from CuInSe2 films indicative of significant improvement in crystalline quality and substantial reduction in the point defect density. © 1996 American Institute of Physics.
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78.66.Fd III-V semiconductors
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

On the electronic interaction between additives and semiconducting oxide gas sensors

D. S. Vlachos, C. A. Papadopoulos, and J. N. Avaritsiotis

Appl. Phys. Lett. 69, 650 (1996); http://dx.doi.org/10.1063/1.117794 (3 pages) | Cited 16 times

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A model for the electronic interaction between additives and semiconducting oxide gas sensors is presented. The model is based on the depletion layer that is created due to the metal–semiconductor contact forced by the presence of a metallic additive. This depletion layer corresponds to an active grain size that is smaller than the geometrical one. Thus, the work function of the metal is connected to the change of sensor characteristics. Moreover, the dependence of the sensitivity on the amount of the deposited additive is explained on the same basis. Experimental results are presented in the case of tin oxide thin film gas sensors with Pd, Pt, and Ni in the presence of zero grade air and carbon monoxide. The experimental results are in excellent qualitative agreement with the proposed model. © 1996 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Picosecond photoresponse of carriers in Si ion‐implanted Si

Albert Chin, K. Y. Lee, B. C. Lin, and S. Horng

Appl. Phys. Lett. 69, 653 (1996); http://dx.doi.org/10.1063/1.117795 (3 pages) | Cited 32 times

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Picosecond photoresponse of carriers in Si ion‐implanted Si samples has been measured using femtosecond transient reflectivity measurement. A threshold peak implant dose of 1016 cm −2 is required to achieve picosecond carrier lifetime. At this dosage, carrier lifetimes of 0.9 and 1.4 ps are measured for the as‐implanted and 400 °C annealed Si substrates, respectively. The increase in carrier lifetime upon annealing is attributed to the reduction in the concentration of trap and recombination centers. Sheet resistance also shows a strong dependence on the annealing temperature. An eightfold increase in sheet resistance is obtained for annealed samples, and a reduction in hopping conduction, manifested by the e−1/T temperature dependence, may be responsible for the increase in resistance. Further evidence of decreasing hopping conduction can be also observed from the more than two orders of magnitude in reduction of sheet resistance as the peak dosage decreases from 1016 to 1014 cm−2. © 1996 American Institute of Physics.
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72.40.+w Photoconduction and photovoltaic effects
72.80.Cw Elemental semiconductors
78.47.-p Spectroscopy of solid state dynamics

Andreev reflections at interfaces between δ‐doped GaAs and superconducting Al films

R. Taboryski, T. Clausen, J. Bindslev Hansen, J. L. Skov, J. Kutchinsky, C. B. Sørensen, and P. E. Lindelof

Appl. Phys. Lett. 69, 656 (1996); http://dx.doi.org/10.1063/1.117796 (3 pages) | Cited 15 times

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By placing several Si δ‐doped layers close to the surface of a GaAs molecular beam epitaxy–grown crystal, we achieve a compensation of the Schottky barrier and obtain a good Ohmic contact between an in situ deposited (without breaking the vacuum) Al metallization layer and a highly modulation doped (n++) conduction layer embedded below the δ‐doped layers in the GaAs crystal. When cooled to below the critical temperature (≊1.2 K) of Al, superconductivity is induced in the conductive layer of the semiconductor. We have studied the current voltage (I–V) characteristics in a planar geometry where the Al has been removed in a thin stripe. We find a manifestation of the superconducting energy gap and a rich fine structure at injection energies both below and above the gap. © 1996 American Institute of Physics.
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74.45.+c Proximity effects; Andreev reflection; SN and SNS junctions
74.78.-w Superconducting films and low-dimensional structures
73.40.Cg Contact resistance, contact potential

Interface structure of selectively oxidized AlAs/GaAs

T. Takamori, K. Takemasa, and T. Kamijoh

Appl. Phys. Lett. 69, 659 (1996); http://dx.doi.org/10.1063/1.117797 (3 pages) | Cited 28 times

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We present studies of the interface abruptness of selectively oxidized AlAs/GaAs multilayer structures using transmission electron microscopy (TEM). High‐resolution cross‐sectional TEM images reveal that the interfaces between oxidized AlAs and unoxidized regions (GaAs and AlAs) are extremely abrupt on atomic scale. The widths of the transitional region are found to be within 4 monolayers for the interface between oxidized AlAs and unoxidized GaAs and 6.5 nm for the one between oxidized and unoxidized AlAs. The oxide layer thickness is found to decrease gradually from the oxidation front over a length of 200 nm. © 1996 American Institute of Physics.
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68.35.Ct Interface structure and roughness
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
81.65.Mq Oxidation
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

A near‐field scanning optical microscopy study of the uniformity of GaAs surface passivation

Jutong Liu and T. F. Kuech

Appl. Phys. Lett. 69, 662 (1996); http://dx.doi.org/10.1063/1.117798 (3 pages) | Cited 4 times

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We have achieved spatially resolved photoluminescence (PL) from metalorganic vapor phase epitaxy (MOVPE) grown GaAs surfaces by near‐field scanning optical microscopy (NSOM). We have performed the topography, reflection, and PL measurements by NSOM combined with the topography measurements by atomic force microscopy (AFM) on the as‐grown and (NH4)2S‐passivated GaAs samples. The uniformity of GaAs with a thin Al0.65Ga0.35As cap layer has also been studied and compared with the (NH4) 2S treated samples. We found the submicron scale variations in PL intensity which were not correlated to the topographic features. The PL intensity variation was related to the changes in the surface state density. Semiquantitative analyses of the resolution limits of NSOM‐based PL measurements and surface state variations are presented. © 1996 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Rv Passivation

Time‐resolved cathodoluminescence study of carrier relaxation in GaAs/AlGaAs layers grown on a patterned GaAs(001) substrate

D. H. Rich, H. T. Lin, A. Konkar, P. Chen, and A. Madhukar

Appl. Phys. Lett. 69, 665 (1996); http://dx.doi.org/10.1063/1.117799 (3 pages) | Cited 6 times

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We have examined the kinetics of carrier relaxation in three‐dimensionally confined GaAs/AlGaAs layers obtained by growth on prepatterned GaAs(001) with time‐resolved cathodoluminescence (CL). Time‐delayed CL spectra at 87 K reveal that (i) relaxation of hot carriers into the largest 3D confined regions occurs on a time scale of a few hundred ps during the onset of luminescence, and (ii) the luminescence decay time also increases for these larger confined regions, owing to thermal reemission from QWs, diffusion across AlxGa1−xAs barriers, and carrier feeding from surrounding thinner QWs. © 1996 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Fd III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
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