Showing papers in "Applied Physics Letters in 1979"
TL;DR: In this article, a stable and reproducible current-controlled bistable electrical switching has been observed in polycrystalline organic semiconducting films, where the transition from a high-to low-impedance state occurs with delay and switching times of approximately 15 and 10 nsec.
Abstract: Stable and reproducible current‐controlled bistable electrical switching has been observed in polycrystalline organic semiconducting films. The effect has been observed in a lamellar structure with a film of microcrystalline Cu‐TCNQ between Cu and Al electrodes where the Cu‐TCNQ is grown on a Cu substrate via a spontaneous electrolysis technique. The switching effect is insensitive to moisture and is observed over a large temperature range. The current‐voltage characteristics reveal an abrupt decrease in impedance from 2 MΩ to less than 200 Ω at a field strength of 4×103 V/cm. The transition from a high‐ to low‐impedance state occurs with delay and switching times of approximately 15 and 10 nsec, respectively. Switching with high‐power dissipation yields a low‐impedance memory state which can be erased by application of a short current pulse. An interpretation of this behavior is based on the bulk properties of the mixed valence semiconductor Cu‐TCNQ.
480 citations
TL;DR: In this article, it was shown that silicon is isotropically etched by exposure to XeF2(gas) at T = 300 K. The implication of these experimental results for understanding mechanisms associated with plasma etching (including RIE) will be discussed.
Abstract: It is shown that silicon is isotropically etched by exposure to XeF2(gas) at T=300 K. Si etch rates as large as 7000 A/min were observed for P (XeF2) <1.4×10−2 Torr and the etch rate varies linearly with P (XeF2). There was no observable etching of SiO2, Si3N4, or SiC, demonstrating an extremely large selectivity between silicon and its compounds. Therefore, thin masks constructed from silicon compounds can be used for pattern delineation. The implication of these experimental results for understanding mechanisms associated with plasma etching (including RIE) will be discussed.
456 citations
TL;DR: In this article, the authors show that optical bistability can occur in a distributed feedback structure with an intensity-dependent refractive index, and analyze expressions for the transmissivity.
Abstract: We show that optical bistability can occur in a distributed feedback structure with an intensity‐dependent refractive index. Analytical expressions for the transmissivity are obtained and a comparison with Fabry‐Perot‐type devices is presented.
419 citations
TL;DR: In this article, the bistability of a GaAlAs-GaAs−GaAlAs molecular-beam-epitaxially-grown sandwich with 90% reflectivity coatings was observed in a semiconductor.
Abstract: Optical bistability has been observed in a semiconductor for the first time. The bistable etalon consists of a GaAlAs‐GaAs‐GaAlAs molecular‐beam‐epitaxially‐grown sandwich with 90% reflectivity coatings. The bistability is primarily dispersive with the nonlinear refractive index arising from light‐induced changes in exciton absorption. Using light of frequency just below the exciton peak, we observed bistability from 5 to 120 °K with 40‐ns turn‐off and subnanosecond turn‐on times with 1 mW/μm2 holding intensity.
376 citations
TL;DR: In this paper, the discovery of a new photon avalanche region, occurring when pump flux exceeds a certain critical value, has been reported in laser-pumped Pr3+ infrared quantum counters.
Abstract: Studies of laser‐pumped Pr3+ infrared quantum counters have led to the discovery of a new photon avalanche region, occurring when pump flux exceeds a certain critical value. Infrared output near 4.5 μm is associated with the large visible output, and pump power is strongly absorbed. Critical pump power density is in the range 1.2–12.2 W/cm2.
352 citations
TL;DR: In this article, a silicon crystal has been induced by picosecond laser pulses at 532 and 266 nm optical microscopy and electron diffraction revealed the formation of amorphous silicon details of surface morphology are sensitive functions of pulse intensity, energy, wavelength and crystallographic orientation.
Abstract: Ultrafast melting and resolidification on the surface of a silicon crystal has been induced by picosecond laser pulses at 532 and 266 nm Optical microscopy and electron diffraction revealed the formation of amorphous silicon Details of surface morphology are sensitive functions of pulse intensity, energy, wavelength, and crystallographic orientation
287 citations
TL;DR: In this article, a new mechanism is proposed to obtain negative differential resistance in layered heterostructures for conduction parallel to the interface, based on hot-electron thermionic emission from high mobility GaAs into low mobility AlxGa1−xAs.
Abstract: A new mechanism is proposed to obtain negative differential resistance in layered heterostructures for conduction parallel to the interface. The mechanism is based on hot‐electron thermionic emission from high‐mobility GaAs into low‐mobility AlxGa1−xAs. Preliminary calculations indicate that high peak‐to‐valley ratios can be achieved. The transfer speed is estimated to be of the order of 10−11 s. We further show that the concept of hot‐electron thermionic emission can be applicable to a variety of devices.
276 citations
TL;DR: In this article, the orientation of overlayer films induced by artificial surface patterns was proposed as graphoepitaxy, which is a special case of graphopitaxy induced by surface patterns.
Abstract: Uniform crystallographic orientation of silicon films, 500 nm thick, has been achieved on amorphous fused‐silica substrates by laser crystallization of amorphous silicon deposited over surface‐relief gratings etched into the substrates. The gratings had a square‐wave cross section with a 3.8‐μm spatial period and a 100‐nm depth. The 〈100〉 directions in the silicon were parallel to the grating and perpendicular to the substrate plane. We propose that orientation of overlayer films induced by artificial surface patterns be called graphoepitaxy.
270 citations
TL;DR: In this article, the optical stability of a plane parallel semiconductor crystal which forms a Fabry-Perot interferometer using only the natural reflectivity of its surfaces is reported.
Abstract: We report the observation of optical stability for a plane parallel semiconductor crystal which forms a Fabry‐Perot interferometer using only the natural reflectivity of its surfaces. Nonlinear transmission is observed for cw laser intensities above ∼ 100 W/cm2 for radiation at 1895 cm−1 near the energy gap of InSb at 5 K. The effect is interpreted in terms of a very large intensity‐dependent refractive index giving a 5λ/2 optical thickness change for an intensity of ∼2 kW/cm2. Clear bistability is seen in fifth‐order interference, the first such observation above first order in an intrinsic, one‐element system, in addition to regions exhibiting signal amplification. The same crystal also shows strong modulation of the transmission of one laser beam induced by a second, with real signal gain, thus demonstrating an ’’optical transistor.’’
268 citations
TL;DR: In this paper, preferential diffusion of various gases down the grain boundaries in polycrystalline silicon is shown to promote significant changes in the density of defect states in these regions, and the results have important implications for the development of low-cost thin-film silicon photovoltaic devices.
Abstract: Preferential diffusion of various gases down the grain boundaries in polycrystalline silicon is shown to promote significant changes in the density of defect states in these regions. A plasma of monatomic hydrogen provides a significant reduction in both the state density and the accompanying grain‐boundary potential barrier while plasmas of oxygen, nitrogen, and sulfur hexafluoride are shown to increase this density of states. Boundaries passivated with hydrogen have as much as a factor of 1000 larger transconductance after treatment. Hydrogenated barriers are stable over long periods at 375 °C and essentially indefinitely at 23 °C. The results have important implications for the development of low‐cost thin‐film silicon photovoltaic devices.
264 citations
TL;DR: In this paper, it is shown that using optoacoustic phase angle scanning rather than amplitude scanning enables precise measurements of subsurface structure in metal, for some applications the method can be an alternative to x-ray imaging.
Abstract: It is shown that using optoacoustic phase angle scanning rather than amplitude scanning enables precise measurements of subsurface structure in metal. For some applications the method can be an alternative to x‐ray imaging.
TL;DR: In this paper, the authors measured the stress present in thermal SiO2 at temperatures during growth in wet O2 and found that compressive stress on the order of 7×109 dyn/cm2 is generated in the SiO 2 during growth at 975 and 1000 °C.
Abstract: Stress present in thermal SiO2 at temperatures during growth in wet O2 has been measured as a function of growth temperature. During growth at 950 °C and below, compressive stress on the order of 7×109 dyn/cm2 is generated in the SiO2. During growth at 975 and 1000 °C, the SiO2 grows in a stress‐free state. The results, which are consistent with a viscous flow point somewhere between 950 and 975 °C, are of value in avoiding mechanical failure effects in integrated‐circuit processing.
TL;DR: In this article, it was shown that amorphous silicon hydrogen films from silane or silane/argon mixtures are formed by nucleation and growth of islands of average lateral dimensions ∼100 A. If these islands do not coalesce into a homogeneous film, subsequent growth produces columnar morphology with low density interstitial regions.
Abstract: Using transmission and scanning electron microscopy, it is shown that plasma deposition of amorphous silicon hydrogen films from silane or silane/argon mixtures proceeds via nucleation and growth of islands of average lateral dimensions ∼100 A. If these islands do not coalesce into a homogeneous film, subsequent growth produces columnar morphology with low‐density interstitial regions. There is a strong correlation between the columnar structure and the presence of nonradiative recombination centers.
TL;DR: In this paper, an elastic recoil detection (ERD) analysis technique for profiling 1H in the near surface regions of solids using a 2.5MeV Van de Graaff accelerator commonly used for ion-backscattering analysis is described.
Abstract: We describe an elastic recoil detection (ERD) analysis technique for profiling 1H in the near‐surface regions of solids using a 2.5‐MeV Van de Graaff accelerator commonly used for ion‐backscattering analysis. Energy analysis of 1H forward scattered by 2.4‐MeV 4He incident on the target tilted at an angle of ∼75° yields a depth resolution of ≲700 A and a sensitivity of better than 0.1 at.% for 1H to depths of ≲0.6 μm in solids.
TL;DR: In this article, a liquid metal gallium ion source was imaged by a unity-magnification single-gap accelerating lens with a postlens deflector to form a focused scanning probe.
Abstract: A liquid‐metal gallium‐ion source was imaged by unity‐magnification single‐gap accelerating lens with a postlens deflector to form a focused scanning probe. We report the dependence of the probe diameter and probe current on the lens acceptance half‐angle. The results range between probe diameters of 1000 and 5000 A at currents of 0.12–3.0 nA for half‐angles of 1.2–6 mrad. The current density and brightness at the target for the 1000‐A‐diam 57‐kV probe were 1.5 A/cm2 and 3.3×106 A/cm2 sr, respectively. Astigmatic probes were also produced with dimensions smaller than 1000 A.
TL;DR: In this paper, the scattering rates for the electron impurity and the electron-phonon interactions in semiconductor multilayer heterojunction structures were calculated, and it was found that phonon scattering is enhanced in such structures, whereas, impurity scattering can be strongly reduced at low temperatures as found experimentally.
Abstract: The scattering rates for the electron‐impurity and the electron‐phonon interactions in semiconductor multilayer heterojunction structures are calculated. It is found that phonon scattering is enhanced in such structures, whereas, impurity scattering can be strongly reduced at low temperatures as found experimentally.
TL;DR: In this paper, the authors proposed a superlattice which consists of alternating (100) layers of CdTe and HgTe and the band gap can be adjustable from 0 to 1.6 eV depending on the thicknesses of the layers.
Abstract: We propose a new material which could be useful in a number of infrared optoelectronic devices. The material consists of alternating (100) layers of CdTe and HgTe. The band gap of this superlattice is adjustable from 0 to 1.6 eV depending on the thicknesses of the CdTe and HgTe layers. Details of the band‐gap variation and the character of the band‐edge states are presented.
TL;DR: In this article, a planar-type p-n junction is formed in an InP window layer, separated from a light absorbing InGaAsP layer, yielding an avalanche gain of 3000 and a dark current density as low a 1 μA/cm2 at 0.5 Vb.
Abstract: Distinct improvements in avalanche‐gain and dark‐current characteristics have been made in InGaAsP heterostructure APD’s. A planar‐type p‐n junction is formed in an InP window layer, separated from a light‐absorbing InGaAsP layer. This APD structure has yielded an avalanche gain of 3000 and a dark‐current density as low a 1 μA/cm2 at 0.5 Vb.
TL;DR: In this article, the authors proposed a model for unique acoustic material signatures (AMS) obtained in the reflection acoustic microscope, which showed that they result from interference between two components reradiated into the immerson fluid at the materials critical Rayleigh angle ϑR.
Abstract: Unique acoustic material signatures (AMS) may be obtained in the reflection acoustic microscope. The proposed model shows that they result from interference between two components reradiated into the immerson fluid at the materials critical Rayleigh angle ϑR. The characteristic period ΔzN of this interference signature varies as the square of the Rayleigh wave velocity and is empirically given by ΔzN=λR/sinϑR, where λR is the Rayleigh wavelength. Materials covering a greater than 3 : 1 velocity range agree well with this physical model. Substitution of the longitudinal wave velocity in the expression extends the range of measurable AMS to acoustically slower materials. A variety of applications for AMS is suggested.
TL;DR: In this article, the state of polarization at the output end of a long nominally circular single-mode optical fiber is stabilized by an active control system, which contains a polarimeter and two electromagnetic fiber squeezers which introduce variable amounts of stress birefringence directly into the fiber.
Abstract: The state of polarization at the output end of a long nominally circular single‐mode optical fiber is stabilized by an active control system. It contains a polarimeter and two electromagnetic fiber squeezers which introduce variable amounts of stress birefringence directly into the fiber, compensating for the effects of changing intrinsic fiber birefringence.
TL;DR: In this article, surface analyses combined with barrier height studies indicate that barriers made with low-work-function metals (Yb, Mg, and Mn) are essentially Cu/Cu2O cells due to reduction of the Cu2O surface and subsequent interdiffusion phenomena.
Abstract: Surface analyses combined with barrier‐height studies indicate that Cu2O Schottky barriers made with low‐work‐function metals (Yb, Mg, and Mn) are essentially Cu/Cu2O cells due to reduction of the Cu2O surface and subsequent interdiffusion phenomena. The copper‐rich region essentially determines the barrier height. As a result, efficiencies of Cu2O Schottky‐barrier solar cells are usually less than 1%. It is concluded that to achieve significant increases in Cu2O cell efficiencies, MIS or heterojunction device structures must be utilized.
TL;DR: In this paper, a singlemode optical fiber encircling the conductor is used to measure currents on highvoltage lines, and with ∼10 m of fiber, coiled with a 3-cm radius, the authors obtained 0.25 mrad/A polarization rotation, permitting measurement of currents of 0.2-2000 A.
Abstract: To measure currents on high‐voltage lines, the Faraday rotation is used in a single‐mode optical fiber encircling the conductor. Disturbing linear birefringence is suppressed by twisting the fiber. With ∼10 m of fiber, coiled with a 3‐cm radius, we obtain 0.25 mrad/A polarization rotation, permitting measurement of currents of 0.2–2000 A.
TL;DR: In this article, a one-to-one correspondence between deformation-produced dark spots in cathodoluminescence micrographs and dislocations was demonstrated in n-type CdTe by comparing the CL pattern with the etch-pit pattern developed with a new etchant.
Abstract: A one‐to‐one correspondence between deformation‐produced dark spots in cathodoluminescence (CL) micrographs and dislocations has been demonstrated in n‐type CdTe by comparing the CL pattern with the etch‐pit pattern developed with a new etchant which has been ascertained to reveal dislocations by a successive polishing and etching method.
TL;DR: In this paper, the introduction and annealing of defect states in silicon stressed at 770 °C in compression have been studied by capacitance transient spectroscopy on Schottky-barrier structures.
Abstract: The introduction and annealing of defect states in silicon stressed at 770 °C in compression have been studied by capacitance transient spectroscopy on Schottky‐barrier structures. High‐resistivity n‐type samples are converted to p type. Low resistivity n‐type samples are compensated but recover upon annealing. A large variety of defect states are observed with prominent features at E (0.68) after deformation. The spectra simplify upon annealing at 900 °C to two dominant states, E (0.38) and H (0.35).
TL;DR: A survey of the metal-semiconductor interface chemistry for GaAs and seven metals, Ag, Al, Au, Cr, Fe, Sn, and Ti, by using x-ray photoemission spectroscopy (XPS) is reported as discussed by the authors.
Abstract: A survey of the metal‐semiconductor interface chemistry for GaAs and seven metals, Ag, Al, Au, Cr, Fe, Sn, and Ti, by using x‐ray photoemission spectroscopy (XPS) is reported Sn and Ag each form an abrupt inert interface with GaAs Au, Al, Fe, Cr, and Ti each form a chemically reacted nonabrupt interface with a trend for increasing dissociation of GaAs in the order listed Also reported is the first observation of epitaxial Fe growth on GaAs
TL;DR: In this paper, the authors used polarization coherent anti-Stokes Raman spectroscopy to detect weak Raman modes with cross sections as low as 2×10−4 times that of the 992−cm−1 mode of benzene.
Abstract: We show that by using polarization coherent anti‐Stokes Raman spectroscopy, the detection sensitivity of weak Raman modes is greatly enhanced. The spectra of the real part, the imaginary part, and the absolute magnitude of the resonant nonlinear susceptibility can be separately measured. Raman modes with cross sections as low as 2×10−4 times that of the 992‐cm−1 mode of benzene are detectable with less than 10‐kW‐peak‐power lasers.
TL;DR: In this article, the laser-induced heterogeneous photochemical processes may have application in several areas of microelectronics including metallization, etching, and growth of semiconductor films.
Abstract: Metal deposits with features smaller than 2 μm have been produced by the uv laser‐induced photodissociation of organometallic compounds. Such laser‐induced heterogeneous photochemical processes may have application in several areas of microelectronics including metallization, etching, and growth of semiconductor films.
TL;DR: In this article, the mechanism of thermal oxidation of silicon in dry oxygen was studied using 18O as the tracer, and the results suggest that the oxide grows mainly through long-range migration of oxygen, favoring models based on the transport of molecular oxygen.
Abstract: The mechanism of thermal oxidation of silicon in dry oxygen was studied using 18O as the tracer. SiO2 layers first grown in natural oxygen (1300–3000 A) were further grown in highly 18O‐enriched oxygen for 8.5 h at 930 °C. 18O profiling was carried out using the 629‐keV narrow resonance in the nuclear reaction 18O(p,α) 15N. The resulting SiO2 films consist of two 18O‐rich layers, 7% near the SiO2 surface and 93% near the Si‐SiO2 interface, while the bulk 18O concentration is very low. The results suggest that the oxide grows mainly through long‐range migration of oxygen, favoring models based on the transport of molecular oxygen.
TL;DR: In this article, a trasverseflow oxygen-iodine laser was used for the extraction of chemically generated O2(1Δ) energy, and the measured power extraction efficiency with off-optimal outcoupling was 15%.
Abstract: Efficient extraction of chemically generated O2(1Δ) energy has been obtained in a trasverse‐flow oxygen‐iodine laser. The measured power extraction efficiency with off‐optimal outcoupling was 15%. Output powers in excess of 100 W were obtained for periods of up to 3 min.
TL;DR: In this paper, the authors reported that the active area efficiency of a 3.1-cm2 silicon solar cell was close to the best silicon cell yet produced with 17.6% active-area efficiency (AM1, 28°C).
Abstract: Major new results are reported for silicon MIS solar cells. Open‐circuit voltages up to 655 mV (AM0, 25 °C) have been obtained for 0.1‐Ω cm silicon wafers, substantially higher than previously reported for any other silicon solar cell. On an active‐area basis, the efficiency of these high‐output‐voltage cells is close to the best silicon cell yet produced with 17.6% active‐area efficiency (AM1, 28 °C) for a 3‐cm2 cell.