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2 Sep 1996

Volume 69, Issue 10, pp. 1343-1495

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Ground state exciton lasing in CdSe submonolayers inserted in a ZnSe matrix

N. N. Ledentsov, I. L. Krestnikov, M. V. Maximov, S. V. Ivanov, S. L. Sorokin, P. S. Kop’ev, Zh. I. Alferov, D. Bimberg, and C. M. Sotomayor Torres

Appl. Phys. Lett. 69, 1343 (1996); http://dx.doi.org/10.1063/1.117430 (3 pages) | Cited 56 times

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We study optical properties of ZnMgSSe‐ZnCdSe structures with CdSe submonolayers inserted in a ZnSe matrix. Remarkably high exciton oscillator strength is found in ultrashort‐period submonolayer CdSe‐ZnSe superlattices, as compared to ZnCdSe quantum wells of comparable average width and Cd composition. In conventional ZnCdSe quantum wells the lasing occurs at energies ∼30 meV below the free heavy‐hole exciton transition revealed in photoluminescence and in optical reflectance spectra. In the CdSe submonolayer superlattices lasing occurs at energies in the very vicinity of the heavy hole exciton resonance, directly in the region of strongly‐enhanced exciton‐induced modulation of the reflectance spectrum, and, consequently, refractive index change. We attribute the effects observed to exciton localization by potential fluctuations caused by nanoscale CdSe islands formed during submonolayer deposition. © 1996 American Institute of Physics.
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78.66.Hf II-VI semiconductors
71.35.Gg Exciton-mediated interactions

Photorefractive two‐wave mixing bistability in Fe: KNbO3 without external feedback: Increasing gain bistability

Bradley M. Jost

Appl. Phys. Lett. 69, 1346 (1996); http://dx.doi.org/10.1063/1.117431 (3 pages) | Cited 3 times

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The observation of photorefractive two‐wave mixing bistability without external feedback is reported. Hysteresis with an on/off contrast ratio of 30 was obtained through the interaction of two 514.5 nm laser beams within a Fe: KNbO3 crystal. A signal beam modulation rate less than 25 mHz was necessary to obtain the hysteresis when the total optical irradiance of the pump and signal beams was ∼1 mW/mm2. The data are shown to correspond well with a two‐state increasing gain model. © 1996 American Institute of Physics.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.70.Mp Nonlinear optical crystals

Mechanism of self‐organized light‐induced scattering in periodically poled lithium niobate

B. Sturman, María Aguilar, F. Agulló‐López, V. Pruneri, P. G. Kazansky, and D. C. Hanna

Appl. Phys. Lett. 69, 1349 (1996); http://dx.doi.org/10.1063/1.117432 (3 pages) | Cited 6 times

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It is shown that the photorefractive grating produced by a pair of plane waves in periodically poled lithium niobate includes an additional set of spatial harmonics related to the periodic domain structure. This results in new schemes for photorefractive wave coupling. Using the modified phase matching conditions and the concept of optical oscillation we accurately describe the position of the diffraction peaks and explain the main characteristics of self‐organized photoinduced scattering reported recently. © 1996 American Institute of Physics.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.25.Fx Diffraction and scattering

LiNbO3 phase gratings prepared by a single excimer pulse through a silica phase mask

G. P. Luo, Y. L. Lu, Y. Q. Lu, X. L. Guo, S. B. Xiong, C. Z. Ge, Y. Y. Zhu, Z. G. Liu, N. B. Ming, J. W. Wu, D. S. Ding, and Z. H. Lu

Appl. Phys. Lett. 69, 1352 (1996); http://dx.doi.org/10.1063/1.117433 (3 pages) | Cited 7 times

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A transmission silica phase mask grating was used to fabricate LiNbO3 wafer phase gratings by a single excimer pulse at 248 nm. The morphologies of the LiNbO3 wafer gratings were studied with an atomic force microscope as well as an optical microscope. The crystal structures of the gratings were characterized by x‐ray diffraction and three new crystal phases were found at the gratings’ surface besides the substrate phase of LN (110). © 1996 American Institute of Physics.
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42.79.Dj Gratings
42.82.Cr Fabrication techniques; lithography, pattern transfer

Differential reflectance spectroscopy of GaAs/GaAlAs at elevated temperatures

P. Kraisingdecha and M. Gal

Appl. Phys. Lett. 69, 1355 (1996); http://dx.doi.org/10.1063/1.117434 (3 pages) | Cited 6 times

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Differential reflectance (DR), a contactless optical modulation technique, has been used to study GaAs/AlGaAs quantum wells and bulk GaAs, over a wide temperature range (77<T<600 K). The objective of this study was to demonstrate that DR, unlike most optical modulation spectroscopies, can be effectively and effortlessly used at elevated temperatures, and, thus, provide considerable potential for in situ monitoring. We have used DR to measure the temperature dependence of several critical points of GaAs and AlxGa1−xAs (x=0.31). © 1996 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.40.Fy Semiconductors

Mechanisms of upconverted fluorescence in an Er3+ doped LiNbO3 single crystal

J. J. Ju, T. Y. Kwon, S. I. Yun, M. Cha, and H. J. Seo

Appl. Phys. Lett. 69, 1358 (1996); http://dx.doi.org/10.1063/1.117435 (3 pages) | Cited 22 times

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Two different upconversion mechanisms leading to green fluorescence in an Er3+ doped LiNbO3 crystal have been investigated with pulse laser excitations at the wavelengths of 1064 and 980 nm. In the case of the 1064 nm pump, the Er3+ ions become excited by the phase‐matched second harmonic wave generated in the LiNbO3 crystal, whereas sequential two‐photon absorption is mainly responsible for the excitation with the 980 nm pump. The second harmonic excitation is of an order of magnitude more efficient than the sequential two photon excitation in the upconversion of the near‐infrared pump photons to the green fluorescence. © 1996 American Institute of Physics.
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42.62.Fi Laser spectroscopy
42.70.Hj Laser materials
78.55.Hx Other solid inorganic materials

Electric field measurements in an argon glow discharge using laser spectroscopy

Y. W. Choi, M. D. Bowden, and K. Muraoka

Appl. Phys. Lett. 69, 1361 (1996); http://dx.doi.org/10.1063/1.117436 (3 pages) | Cited 23 times

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Direct measurements of the electric field in the sheath of a dc glow discharge were made using laser spectroscopic measurements of argon atoms. The effect of the electric field on the 4s⇒7f transitions was used to determine the electric field. Both laser opto‐galvanic spectra and laser‐induced fluorescence spectra were obtained. The magnitude of the electric field was determined using an experimentally obtained calibration of the change in wavelength produced by the electric field. © 1996 American Institute of Physics.
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52.80.Hc Glow; corona
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Production of intense atomic nitrogen beam used for doping and synthesis of nitride film

Ning Xu, Yuan‐Cheng Du, Zhi‐Feng Ying, and Fu‐Ming Li

Appl. Phys. Lett. 69, 1364 (1996); http://dx.doi.org/10.1063/1.117437 (3 pages) | Cited 10 times

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An arc‐heated source for producing an intense nitrogen atom beam with intensity of 1019 atoms/sr s and kinetic energies of 0.5–4 eV is presented. The arc discharge has been carried out in pure nitrogen gas and maintained stable in an arc operating pressure of 30–300 Torr. The beam kinetic energy changes with the arc pressure, and is insensitive to the arc current. Auger electron spectroscopy analysis showed that a TiNO layer with a thickness of about 100 Å was formed on the smooth Ti wafer at room temperature with interaction of the atomic nitrogen beam. © 1996 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
07.77.Gx Atomic and molecular beam sources and detectors
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Evaluation of depth profile of defects in ultrathin Si film on buried SiO2 formed by implanted oxygen

Atsushi Ogura, Toru Tatsumi, Tomohiro Hamajima, and Hiroaki Kikuchi

Appl. Phys. Lett. 69, 1367 (1996); http://dx.doi.org/10.1063/1.117438 (3 pages) | Cited 14 times

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A simple technique is presented for evaluating defect profiles in ultrathin Si films on buried SiO2 formed by implanted oxygen. A combination of thinning by sacrificial oxidation and epitaxial film growth by UHV‐CVD is used. By measuring the defect density of the epitaxial film with respect to the thickness prior to epitaxial growth, the profile of the initial defect density can easily be evaluated. This technique is applied to evaluate the Si on insulator structure fabricated by state‐of‐the‐art technique, in which low dose oxygen implantation (∼4×1017 cm−2) and high temperature internal oxidation processes are used. The defect density at the surface of the film is 250 cm−2. However, as the buried interface is approached, the defect density increases. The defect density at 20 nm from the buried interface is as high as 6×105 cm−2. A defect generation mechanism is also discussed. © 1996 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.S- Impurities in crystals

Anisotropy of hexagonal boron nitride core absorption spectra by x‐ray Raman spectroscopy

N. Watanabe, H. Hayashi, Y. Udagawa, K. Takeshita, and H. Kawata

Appl. Phys. Lett. 69, 1370 (1996); http://dx.doi.org/10.1063/1.117439 (3 pages) | Cited 19 times

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B as well as N core excitation spectra of hexagonal boron nitride (h‐BN) have been studied by means of x‐ray Raman scattering (XRS) spectroscopy. Transitions from 1s core to σ∗ and π∗ states are completely distinguished by anisotropy measurements of XRS, thus making an unambiguous assignment to the symmetries of excited states and offering a sound basis to characterize h‐BN with core absorption spectroscopy. © 1996 American Institute of Physics.
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61.05.cf X-ray scattering (including small-angle scattering)
78.30.Fs III-V and II-VI semiconductors
07.85.-m X- and γ-ray instruments

Device grade microcrystalline silicon owing to reduced oxygen contamination

P. Torres, J. Meier, R. Flückiger, U. Kroll, J. A. Anna Selvan, H. Keppner, A. Shah, S. D. Littelwood, I. E. Kelly, and P. Giannoulès

Appl. Phys. Lett. 69, 1373 (1996); http://dx.doi.org/10.1063/1.117440 (3 pages) | Cited 79 times

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As‐deposited undoped microcrystalline silicon (μc‐Si:H) has in general a pronounced n‐type behavior. Such a material is therefore often not appropriate for use in devices, such as p‐i‐n diodes, as an active, absorbing i layer or as channel material for thin‐film transistors. In recent work, on p‐i‐n solar cells, this disturbing n‐type character had been successfully compensated by the ‘‘microdoping’’ technique. In the present letter, it is shown that this n‐type behavior is mainly linked to oxygen impurities; therefore, one can replace the technologically delicate microdoping technique by a purification method, that is much easier to handle. This results in a reduction of oxygen impurities by two orders of magnitude; it has, furthermore a pronounced impact on the electrical properties of μc‐Si:H films and on device performance, as well. Additionally, these results prove that the unwanted donor‐like states within μc‐Si:H are mainly due to extrinsic impurities and not to structural native defects. © 1996 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.61.Cw Elemental semiconductors
84.60.Jt Photoelectric conversion

Interactions of ion‐implantation‐induced interstitials with boron at high concentrations in silicon

T. E. Haynes, D. J. Eaglesham, P. A. Stolk, H.‐J. Gossmann, D. C. Jacobson, and J. M. Poate

Appl. Phys. Lett. 69, 1376 (1996); http://dx.doi.org/10.1063/1.117441 (3 pages) | Cited 55 times

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Ion implantation of Si (60 keV, 1×1014/cm2) has been used to introduce excess interstitials into silicon predoped with high background concentrations of B, which were varied between 1×1018 and 1×1019/cm3. Following post‐implantation annealing at 740 °C for 15 min to allow agglomeration of the available interstitials into elongated {311} defects, the density of the agglomerated interstitials was determined by plan‐view transmission electron microscopy observation of the defects. We report a significant reduction in the fraction of excess interstitials trapped in {311} defects as a function of boron concentration, up to nearly complete disappearance of the {311} defects at boron concentrations of 1×1019/cm3. The reduction of the excess interstitial concentration is interpreted in terms of boron‐interstitial clustering, and implications for transient‐enhanced diffusion of B at high concentrations are discussed. © 1996 American Institute of Physics.
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61.72.Yx Interaction between different crystal defects; gettering effect
61.72.uf Ge and Si
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

Development of an optically recording velocity interferometer system for laser induced shock waves measurements

E. Moshe, E. Dekel, Z. Henis, and S. Eliezer

Appl. Phys. Lett. 69, 1379 (1996); http://dx.doi.org/10.1063/1.117587 (3 pages) | Cited 12 times

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An optically recording velocity interferometer system, ORVIS, was developed for measurements of the time evolution of the free surface and the particle velocity in laser induced shock waves experiments. This system produces interference fringe shifts which are proportional to the Doppler shift of a laser beam reflected from the moving surface. These fringe shifts are recorded with a high speed electronic streak camera, which has a 70 ps time resolution. Using this method, the free surface velocity was measured with an accuracy better than 5% and the pressure in laser shocked aluminum targets was calculated. Shock waves of order of hundreds of kilobars are produced by a Nd:YAG laser system with a wavelength of 1.06 μm, pulse width of 5 ns (FWHM) and energy in the range (30–50) J, focused to spots diameters in the range (200–1000) μm. The dynamic spall strength reported here for Al is (14.47±1.45) kbar for a strain rate of ε∼8×106s−1, consistent with studies performed with other methods. © 1996 American Institute of Physics.
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62.50.-p High-pressure effects in solids and liquids
07.60.Ly Interferometers

Microstructure fabrication using oxidation on partially Ga‐terminated Si(111) surfaces

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

Appl. Phys. Lett. 69, 1382 (1996); http://dx.doi.org/10.1063/1.117588 (3 pages) | Cited 2 times

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Oxidation of partially Ga‐terminated Si(111) surfaces with clean 7×7 striped areas along atomic step edges was investigated using scanning reflection electron microscopy. Molecular oxygen exposure of 100 L at the substrate temperatures of 410 °C oxidized Ga atoms on the Ga‐terminated areas as well as Si atoms on the clean 7×7 areas. The Ga oxides were selectively desorbed over the Si oxides during annealing. This results in the formation of stripe‐patterned Si oxides on the surface. After growth of an 8‐monolayer Si film and subsequent annealing, Si grooves with a depth of about 1 nm and a width around 200 nm were formed along the step edges by excess Si‐assisted thermal desorption of the Si oxides. © 1996 American Institute of Physics.
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68.35.Dv Composition, segregation; defects and impurities
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
81.65.Mq Oxidation

Selective oxidation of buried AlGaAs versus AlAs layers

Kent D. Choquette, K. M. Geib, H. C. Chui, B. E. Hammons, H. Q. Hou, T. J. Drummond, and Robert Hull

Appl. Phys. Lett. 69, 1385 (1996); http://dx.doi.org/10.1063/1.117589 (3 pages) | Cited 44 times

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We report significant differences between the properties of buried oxides converted from AlGaAs and AlAs layers using selective wet oxidation. Layers of AlxGa1−xAs with x≥0.96 exhibit crystallographic dependent oxidation rates, while for layers with x≤0.92 the oxidation rate is isotropic. Mesas containing partially oxidized layers of AlAs are unstable to rapid thermal cycling and exhibit excessive strain at the oxide terminus, while mesas containing partially oxidized layers of AlGaAs are robust and lack evidence of strain. Finally, the oxidation of AlGaAs layers, rather than AlAs, is found to provide robust oxide apertures for reliable vertical‐cavity surface emitting lasers. © 1996 American Institute of Physics.
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81.65.Mq Oxidation
68.35.Gy Mechanical properties; surface strains
42.55.Px Semiconductor lasers; laser diodes

Actinometric thermoluminescence response of KCl1−xBrx:Eu2+ mixed crystals

B. Castañeda, R. Aceves, T. M. Piters, M. Barboza‐Flores, R. Meléndrez, and R. Pérez‐Salas

Appl. Phys. Lett. 69, 1388 (1996); http://dx.doi.org/10.1063/1.117590 (3 pages) | Cited 9 times

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Europium‐doped KCl1−xBrx mixed crystals have been studied as a selective ultraviolet (UV) detector material in the actinometric region (200–300 nm). Thermoluminescence glow curves of room‐temperature UV‐irradiated samples were analyzed as a function of composition x and irradiation wavelength. A thermoluminescence enhancement, relative to the pure KCl and KBr end components is found; for 210–300 nm irradiation the KCl40Br60:Eu2+ solid solution presents a significant increase in thermoluminescence efficiency. © 1996 American Institute of Physics.
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78.60.Kn Thermoluminescence
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Cu precipitation in Cr ribbon of Cu‐15 wt % Cr in situ composite

Y. Jin, K. Adachi, T. Takeuchi, and H. G. Suzuki

Appl. Phys. Lett. 69, 1391 (1996); http://dx.doi.org/10.1063/1.117591 (2 pages) | Cited 2 times

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Although the solubility of Cu in Cr is negligible in the equilibrium state, Cu precipitates were discovered in extensively cold‐rolled Cr ribbons of Cu‐15 wt % Cr in situ composite by means of analytical transmission electron microscopy (TEM) and high‐resolution electron microscopy (HREM). The precipitation sequence was found to be a Cu‐rich cluster ⇒ Cu GP zone ⇒ Cu equilibrium phase. © 1996 American Institute of Physics.
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81.30.Mh Solid-phase precipitation
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Epitaxial superlattices of TiAg alloy/MgO grown on MgO(001)

Tetsuo Kado

Appl. Phys. Lett. 69, 1393 (1996); http://dx.doi.org/10.1063/1.117592 (3 pages) | Cited 1 time

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High crystalline quality epitaxial metal/insulator superlattices composed of Ti1−xAgx (0.03<x<0.06) and MgO have been grown on MgO(001) substrates at 273 K by electron beam evaporation in ultrahigh vacuum. X‐ray diffraction measurements and cross‐sectional high‐resolution transmission electron microscopy measurements revealed that the crystal structures of the TiAg alloy and MgO in the superlattices were tetragonal and that the superlattices were so‐called strained‐layer superlattices. The x‐ray rocking curve was measured around one of satellite peaks in the middle angle range, and showed the full width at half‐maximum of the curve was 0.04°–0.05°. © 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.-z Methods of deposition of films and coatings; film growth and epitaxy
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

Two kinds of dopant activation in boron‐doped hydrogenated amorphous silicon–carbon

Masao Isomura, Makoto Tanaka, and Shinya Tsuda

Appl. Phys. Lett. 69, 1396 (1996); http://dx.doi.org/10.1063/1.117593 (3 pages) | Cited 1 time

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Dopant activation occurs via both thermal annealing and light‐soaking in boron‐doped hydrogenated amorphous silicon–carbon prepared at a relatively low temperature. Both kinds of dopant activation probably originate from the same boron sites, because they both cause almost the same increase in dark conductivity, and no light‐induced activation occurs after the thermally induced activation has been attained. The light‐induced states show relaxation even at room temperature and are bistable sites, but the thermally induced states show no significant relaxation and have a more stable configuration. Perhaps, the light‐induced states are caused by microscopic change and the thermally induced states are created with larger scale restructuring. © 1996 American Institute of Physics.
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61.43.Dq Amorphous semiconductors, metals, and alloys
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.61.Jc Amorphous semiconductors; glasses

A single precursor photolitic chemical vapor deposition of silica film using a dielectric barier discharge xenon excimer lamp

Atsushi Yokotani, Noritaka Takezoe, Kou Kurosawa, Tatsushi Igarashi, and Hiromitu Matsuno

Appl. Phys. Lett. 69, 1399 (1996); http://dx.doi.org/10.1063/1.117594 (3 pages) | Cited 16 times

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Silica film has been produced at room temperature by a single precursor process of photolitic chemical vapor deposition using a newly developed Xe excimer lamp. Tetraethoxyorthosilicate (TEOS) has been used as a raw material. Transparent thin film of SiO2 was obtained on single crystalline Al2O3 substrates and its properties were evaluated by means of the reflection Fourier transformation‐infrared spectroscopy, the scanning electron microscopy, and ultraviolet‐visible spectrometry. Consequently, it was found that the main component of the film was SiO2 and very small amounts of residual organic materials were contained. It was also found that the film was very dense and the refractive indices were only 1.7% smaller than that of bulk silica glass. © 1996 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.50.Bc Processes caused by infrared radiation
82.50.Hp Processes caused by visible and UV light
77.55.-g Dielectric thin films

Hardness measurement of thin films: Separation from composite hardness

J. L. He, W. Z. Li, and H. D. Li

Appl. Phys. Lett. 69, 1402 (1996); http://dx.doi.org/10.1063/1.117595 (3 pages) | Cited 10 times

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A composite hardness model based on the function of depth weight factor is presented. The model can be applied to determine the characteristic hardness of surface coatings which are too thin for the hardness to be directly measured. Its application requires only composite hardness data obtained from coated specimens by conventional microhardness measurement. DLC, TiN, and Cu films on substrates of glass, silicon, and AISI 52100 steel were used to verify this composite hardness model. It proved valid for a variety of cases. © 1996 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
62.20.Qp Friction, tribology, and hardness
68.35.Gy Mechanical properties; surface strains
07.10.Cm Micromechanical devices and systems

Optimization of pyroelectricity in the smectic‐C∗ phase of a liquid‐crystalline terpolymer

R. E. Geer, J. Naciri, B. R. Ratna, and R. Shashidhar

Appl. Phys. Lett. 69, 1405 (1996); http://dx.doi.org/10.1063/1.117596 (3 pages)

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The dynamic pyroelectric response in the smectic‐C∗ (SmC∗) phase of a novel class of polysiloxane terpolymers is reported. In these terpolymers methyl groups and two distinct types of mesogenic side chains are attached to the siloxane backbone. Our investigations reveal that the magnitude and temperature dependence of the pyroelectric signal, as well as the temperature range of the SmC∗ phase, can be controlled by varying the relative side‐chain composition. This permits optimization of the pyroelectric properties over a temperature range extending to subambient. Specifically, the pyroelectric coefficient p can be made very nearly temperature independent, and the ratio p/ϵ′ extremely high, making these materials suitable for uncooled infrared detectors. © 1996 American Institute of Physics.
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77.70.+a Pyroelectric and electrocaloric effects
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

Dependence of generation and structures of stacking faults on growing surface stoichiometries in ZnSe/GaAs

L. H. Kuo, K. Kimura, S. Miwa, T. Yasuda, and T. Yao

Appl. Phys. Lett. 69, 1408 (1996); http://dx.doi.org/10.1063/1.117597 (3 pages) | Cited 24 times

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Thin ZnSe films were grown by molecular beam epitaxy on Zn exposed (2×4) As‐stabilized surfaces of GaAs epilayers under varied beam flux ratios. A very low density of faulted defects in the range of ∼ 104/cm2 was generated in samples grown under a condition with a mixture of both (2×1) and weak c(2×2) surface reconstructions at the initial stages of growth. However, an asymmetric distribution on the densities of extrinsic cation‐ and anion‐terminated Shockley‐type stacking faults were generated, respectively, in samples grown under Zn‐ and Se‐rich surface stoichiometries. © 1996 American Institute of Physics.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.35.Dv Composition, segregation; defects and impurities
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.66.Bi Elemental solids
61.66.Dk Alloys

Evidence of interface trap creation by hot‐electrons in AlGaAs/GaAs high electron mobility transistors

Gaudenzio Meneghesso, Alessandro Paccagnella, Youcef Haddab, Claudio Canali, and Enrico Zanoni

Appl. Phys. Lett. 69, 1411 (1996); http://dx.doi.org/10.1063/1.117598 (3 pages) | Cited 12 times

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We report on the hot‐electrons induced degradation in AlGaAs/GaAs high electron mobility transistors (HEMTs), consisting of a decrease in the drain current and an increase in the parasitic drain resistance. The amount of the degradation is proportional to the impact‐ionization rate which is related to the electron energy. Transconductance dispersion measurements and drain current deep level transient spectroscopy (DLTS) have been used to identify interface traps which are located at the AlGaAs/GaAs interface in the gate‐drain access region and are the causes of the observed degradation. © 1996 American Institute of Physics.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.61.Ey III-V semiconductors
85.30.Tv Field effect devices

Recombination dynamics of excitons and biexcitons in a hexagonal GaN epitaxial layer

Yoichi Kawakami, Zhi Gang Peng, Yukio Narukawa, Shizuo Fujita, Shigeo Fujita, and Shuji Nakamura

Appl. Phys. Lett. 69, 1414 (1996); http://dx.doi.org/10.1063/1.117599 (3 pages) | Cited 53 times

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Time‐resolved photoluminescence (PL) spectroscopy has been performed at 18 K on excitonic‐related emissions in an unintentionally doped hexagonal GaN epitaxial layer grown by two‐flow metalorganic chemical vapor deposition (TF‐MOCVD). Under low excitation condition, radiative recombination of A free exciton (EXA: 3.4921 eV) and neutral shallow‐acceptor bound exciton [(A0s,X): 3.4805 eV] dominated the spectrum. Decay time of (A0s,X) emission is relatively long (585 ps) indicating a small number of non‐radiative centers in the layer. At higher excitation densities, new PL peak appeared at 3.4864 eV and grew superlinearly with excitation densities. These features, combined with their transient behavior, suggest that this new emission band is due to the biexciton recombination. © 1996 American Institute of Physics.
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78.66.Fd III-V semiconductors
71.35.-y Excitons and related phenomena
78.47.-p Spectroscopy of solid state dynamics
78.55.Cr III-V semiconductors
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