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6 Aug 1990

Volume 57, Issue 6, pp. 531-636

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Low temperature and selective growth of β‐SiC using the SiH2Cl2/i‐C4H10/HCl/H2 gas system

Yoshio Ohshita

Appl. Phys. Lett. 57, 605 (1990); http://dx.doi.org/10.1063/1.103611 (3 pages) | Cited 10 times

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β‐SiC is grown on a silicon substrate by the chemical vapor deposition method using the SiH2Cl2/i‐C4H10/H2/HCl gas system. Stoichiometric β‐SiC films are obtained with high growth rate at a low temperature of 900 °C. Highly (111) oriented β‐SiC polycrystal is grown on a Si(111) substrate. Moreover, using the above‐mentioned gas system, β‐SiC selective growth is attained on a Si substrate, with no nucleation on the SiO2 area. This letter discusses the i‐C4H10 effects and selective growth condition.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Large photoconductive gain in quantum well infrared photodetectors

G. Hasnain, B. F. Levine, S. Gunapala, and Naresh Chand

Appl. Phys. Lett. 57, 608 (1990); http://dx.doi.org/10.1063/1.103612 (3 pages) | Cited 51 times

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We demonstrate for the first time that a quantum well infrared photodetector based on bound‐to‐continuum state intersubband transitions can have a photoconductive gain much greater than unity similar to extrinsic photoconductors. An optical gain g=8.1 was determined by comparing the optical absorption, responsivity, and noise characteristics of two multiquantum well detectors which were identical in every respect except for having a different number of periods (2 and 20). The results suggest that since the photocarrier lifetime τL is not transit time limited, detector optimization to increase τL or optical coupling can be expected to lead to an improved detectivity D∗.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.50.Pz Photoconduction and photovoltaic effects

Role of step‐flow dynamics in interface roughening and in the spontaneous formation of InGaAs/InP wire‐like arrays

H. M. Cox, D. E. Aspnes, S. J. Allen, P. Bastos, D. M. Hwang, S. Mahajan, M. A. Shahid, and P. C. Morais

Appl. Phys. Lett. 57, 611 (1990); http://dx.doi.org/10.1063/1.103613 (3 pages) | Cited 25 times

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We investigate a morphological instability that causes an InGaAs/InP multiquantum well structure grown on a vicinal (001) InP surface to spontaneously evolve into an array of InGaAs quasi‐one‐dimensional filaments buried in an InP matrix. To explain this behavior, we propose a step‐flow growth model involving different lateral growth velocities for heteroepitaxy and homoepitaxy. A computer simulation based on the model agrees closely with the experiment.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
68.35.Fx Diffusion; interface formation

Pulsed laser heating measurement of relaxation‐induced melting point increase in amorphous Si

M. G. Grimaldi and P. Baeri

Appl. Phys. Lett. 57, 614 (1990); http://dx.doi.org/10.1063/1.103614 (3 pages) | Cited 11 times

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The difference in the melting temperature of unrelaxed and relaxed amorphous silicon has been determined by measuring the energy density threshold for surface melting during nanosecond laser irradiation (λ=347 nm). The melting onset was detected by time‐resolved reflectivity technique. Using particular samples in which a surface unrelaxed layer was generated by reimplanting a 400‐nm‐thick relaxed amorphous Si (a‐Si) the difference in the melting temperature has been determined independently of the thermal properties of the a‐Si. The melting temperature of relaxed a‐Si resulted to be only 3.9% higher than that of unrelaxed a‐Si, while on the basis of calorimetric data an ∼14% difference was expected. The reasons for this discrepancy are discussed. In addition a 24% increase in the product of thermal conductivity and specific heat of a‐Si upon relaxation has been found.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
64.70.D- Solid-liquid transitions
65.20.-w Thermal properties of liquids
65.40.gd Entropy

Reaction between Cu and TiSi2 across different barrier layers

Chin‐An Chang and Chao‐Kun Hu

Appl. Phys. Lett. 57, 617 (1990); http://dx.doi.org/10.1063/1.104249 (3 pages) | Cited 27 times

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The reaction between Cu and TiSi2 is studied with and without barriers, Cu being used for interconnect and TiSi2 as the gate silicide for the metal‐oxide‐semiconductor devices. The barriers include Ta, TiN, and W. Without a barrier, Cu reacts with TiSi2 below 300 °C, forming Cu silicides. An improvement in thermal stability by 50–100 °C is obtained using the barriers, with TiN/Ti being the most effective. A combined use of these barriers, with a final structure of Ta/Cu/Ta/W/TiN/Ti/TiSi2 /Si, suppresses the Cu‐TiSi2 reaction until above 600 °C. The reaction mechanisms involved, and their relation with the reactions between Cu and other silicides, are discussed.
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66.30.Ny Chemical interdiffusion; diffusion barriers
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Vz Semiconductor-metal-semiconductor structures
73.30.+y Surface double layers, Schottky barriers, and work functions

Excitation intensity dependence of photoluminescence in Ga0.52In0.48P

M. C. DeLong, P. C. Taylor, and J. M. Olson

Appl. Phys. Lett. 57, 620 (1990); http://dx.doi.org/10.1063/1.103615 (3 pages) | Cited 57 times

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The excitation intensity dependence of the photoluminescence (PL) from Ga0.52In0.48P grown by organometallic vapor phase epitaxy on GaAs substrates has been investigated as a function of epitaxial layer growth temperature and substrate orientation. It is well known that the degree of ordering and the band‐gap energy of this material are functions of growth conditions. We report here on a PL emission which shifts rapidly with excitation intensity. The rate of emission shift is also a function of growth conditions including substrate orientation. There is, however, no significant correlation between the band‐gap energy and the rate of emission shift in Ga0.52In0.48P. This PL shift is explained in terms of band filling of potential fluctuations that are associated with a microstructure consisting of ordered domains within a disordered matrix.
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78.55.Cr III-V semiconductors
61.50.Ks Crystallographic aspects of phase transformations; pressure effects
61.66.Fn Inorganic compounds

Carrier density dependent photoconductivity in diamond

L. S. Pan, D. R. Kania, P. Pianetta, and O. L. Landen

Appl. Phys. Lett. 57, 623 (1990); http://dx.doi.org/10.1063/1.103616 (3 pages) | Cited 38 times

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Single‐crystal natural diamonds have been intrinsically photoexcited using 2 ps laser pulses. Electron and hole mobilities and decay times are examined as a function of induced carrier density. Two major density dependent effects are observed. First, at high induced carrier densities, a dramatic decrease in the carrier mobility is observed. This is attributed to carrier‐carrier scattering between the electrons and the holes. A model describing carrier‐carrier scattering in silicon and germanium has been scaled to diamond. Second, the decay time of the electrons decreases as the initially photoexcited density increases. A simple one‐level recombination model successfully explains this density dependence. The combination of these two effects results in a minimum in the measured photoconductive decay times.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.40.+w Photoconduction and photovoltaic effects
72.80.Ng Disordered solids

Transient nonlinear optical properties of δ‐doped asymmetric superlattices measured by picosecond electro‐optic sampling

Stephen E. Ralph, Federico Capasso, and Roger J. Malik

Appl. Phys. Lett. 57, 626 (1990); http://dx.doi.org/10.1063/1.103617 (3 pages) | Cited 5 times

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We have performed the first picosecond time‐resolved measurements of the photorefractive and nonlinear absorptive properties of asymmetric GaAs doping superlattices. The lack of inversion symmetry in these structures results in a net photoinduced electric field and, therefore, photorefractive phenomena via the χ(2) of the material. Using the electro‐optic sampling technique, the temporal behavior of the photorefractive, and nonlinear absorption effects are uniquely determined. We have observed peak refractive index changes of 3.8×10−4 at an energy density of 40 fJ/μm2.
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78.20.Jq Electro-optical effects
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
78.20.-e Optical properties of bulk materials and thin films

Fabrication of ultrasmall Nb‐AlOx‐Nb Josephson tunnel junctions

John M. Martinis and R. H. Ono

Appl. Phys. Lett. 57, 629 (1990); http://dx.doi.org/10.1063/1.103618 (3 pages) | Cited 16 times

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We describe a fabrication process to make Nb‐AlOx‐Nb edge junctions with areas as small as 0.0022 μm2 and with current densities from 10 to 24 000 A/cm2. The junction conductance was low for voltages below the superconducting energy gap which indicates good quality tunnel barriers. Coulomb gap measurements obtained when the junctions were in the normal state were used to find the junction capacitance. Junction capacitance as small as 0.18 fF has been measured.
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85.25.Cp Josephson devices
85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.50.+r Tunneling phenomena; Josephson effects

CaNdAlO4 perovskite substrate for microwave and far‐infrared applications of epitaxial high Tc superconducting thin films

M. Berkowski, A. Pajaczkowska, P. Gierłowski, S. J. Lewandowski, R. Sobolewski, B. P. Gorshunov, G. V. Kozlov, D. B. Lyudmirsky, O. I. Sirotinsky, P. A. Saltykov, H. Soltner, U. Poppe, Ch. Buchal, and A. Lubig

Appl. Phys. Lett. 57, 632 (1990); http://dx.doi.org/10.1063/1.104250 (3 pages) | Cited 17 times

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Single‐crystal perovskite calcium‐neodymium aluminate CaNdAlO4 has been grown and tested as a substrate material for high Tc superconducting thin films. The material is chemically stable, can be fabricated into the form of large, twin‐free wafers, permits deposition of epitaxial Y‐Ba‐Cu‐O and Bi‐Sr‐Ca‐Cu‐O films, and exhibits low dielectric permittivity (ϵ≂20) and very low losses (tan δ≂10−3 at 100 K) at sub‐THz frequencies. Its high potential in microwave applications of thin‐film high Tc superconductors is clearly demonstrated.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
FREE

Comment on ‘‘Observation of magnetic hysteresis loop of the perminvar type in worked Co‐based amorphous alloys’’[Appl. Phys. Lett. 36, 339 (1980)]

M. Tejedor and H. Rubio

Appl. Phys. Lett. 57, 635 (1990); http://dx.doi.org/10.1063/1.104251 (2 pages) | Cited 1 time

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Abstract Unavailable
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75.50.Kj Amorphous and quasicrystalline magnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
78.20.Ls Magneto-optical effects
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