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15 Jun 1984

Volume 55, Issue 12, pp. 4149-4451

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Theoretical analysis of interacting dimers thermal desorption

E. E. Mola

J. Appl. Phys. 55, 4149 (1984); http://dx.doi.org/10.1063/1.333032 (5 pages) | Cited 3 times

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First‐order thermal desorption of interacting dimers is investigated using the lattice gas model. Dimers are assumed to interact if they occupy only nearest‐neighbor lattice sites. A single type of site is used. By choosing an appropriate sublattice, able to describe first‐order desorption of interacting dimers, the grand partition function is derived using the Bethe approximation. The rate of thermal desorption is written using absolute rate theory. The calculated thermal desorption spectra show two peaks, although a single binding state was considered.
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05.50.+q Lattice theory and statistics (Ising, Potts, etc.)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Equilibrium distributions of electric field in a cell with adsorbed charge at the surfaces

R. N. Thurston

J. Appl. Phys. 55, 4154 (1984); http://dx.doi.org/10.1063/1.333033 (8 pages) | Cited 14 times

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Ionic charge that is stuck at the solid‐liquid surface attracts a diffuse layer of ions of the opposite sign in the liquid. The asymmetry in the electric field distribution that results when an applied field is combined with the intrinsic field in the diffuse charge layer has been cited as a possible cause of the dc switching effect observed in liquid crystal displays based on bistable boundary layer configurations [Robert B. Meyer and R. N. Thurston, Appl. Phys. Lett. 43, 342 (1983)]. Since the ratio of Debye screening length LD to cell depth d is an important parameter, it is useful to solve for the static equilibrium field distribution under constant voltage in a finite cell where LD/d is not small. This problem is solved here.
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41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems
66.10.-x Diffusion and ionic conduction in liquids
82.45.-h Electrochemistry and electrophoresis
61.30.-v Liquid crystals

Rapid isothermal annealing of As‐, P‐, and B‐implanted silicon

S. R. Wilson, W. M. Paulson, R. B. Gregory, A. H. Hamdi, and F. D. McDaniel

J. Appl. Phys. 55, 4162 (1984); http://dx.doi.org/10.1063/1.333034 (9 pages) | Cited 34 times

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Single‐crystal silicon wafers have been implanted with As, P, and B to doses of 1×1013–1×1016/cm2 and given a transient anneal using a Varian IA‐200 Rapid Isothermal Annealer. The system uses infrared radiation to heat the wafers to temperatures in excess of 1000 °C for times on the order of 10 sec. Sheet resistance and Hall measurements have been used to determine the effect of the anneal on the electrical properties of the wafers. Rutherford backscattering and secondary ion mass spectroscopy have been used to measure lattice damage and dopant profiles before and after annealing. As and P are lost during the anneal unless the wafer is capped. Complete activation can be achieved with very little dopant diffusion. Residual damage is minimal in (100) oriented wafers that had been implanted with As. However, for (111) wafers damage is less in (111) wafers implanted to doses ≥5.0×1015/cm2, than in (111) wafers implanted to doses ≤5.0×1015/cm2. The diffusion of As during this transient anneal has been modeled using a concentration enhanced diffusion coefficient and the wafer temperature profile obtained from an optical pyrometer.
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61.72.U- Doping and impurity implantation
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
61.80.Jh Ion radiation effects

The effect of pressure on the semiconductor‐to‐metal transition temperature in tin and in dilute Sn–Ge alloys

F. Vnuk, A. De Monte, and R. W. Smith

J. Appl. Phys. 55, 4171 (1984); http://dx.doi.org/10.1063/1.333035 (6 pages) | Cited 9 times

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The pressure/temperature characteristics of the grey (semiconductor) tin→white (metal) tin transition in pure tin and dilute Sn–Ge alloys has been examined by following electrical resistance changes in strip specimens. It is shown that grey tin→white tin phase boundary has a slope of −48.4±6 K/kbar, in good agreement with thermodynamic predictions.
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64.70.K- Solid-solid transitions
64.70.D- Solid-liquid transitions
62.50.-p High-pressure effects in solids and liquids
64.60.-i General studies of phase transitions

Phase transformations in ion‐mixed metastable (GaSb)1−x(Ge2)x semiconducting alloys

K. C. Cadien, B. C. Muddle, and J. E. Greene

J. Appl. Phys. 55, 4177 (1984); http://dx.doi.org/10.1063/1.333036 (10 pages) | Cited 14 times

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Low energy (75–175 eV) Ar+ ion bombardment during film deposition has been used to produce well‐mixed amorphous GaSb/Ge mixtures which, when annealed, transform first to single phase polycrystalline metastable (GaSb)1−x(Ge2)x alloys before eventually transforming to the equilibrium two‐phase state. At 500 °C, for example, the annealing time ta required for the amorphous to crystalline metastable (ACM) transformation was ∼10 min, while ta for the crystalline metastable to equilibrium (CME) transformation was >6 h. The exothermic enthalpy of crystallization and the onset temperature of the ACM transition were determined as a function of alloy composition using differential thermal analysis. The thermodynamic data was then used to calculate the surface energy per unit area σ of the amorphous/metastable‐crystal interface. σ was found to exhibit a minimum between x=0.3 and 0.4. The driving energy for the transition from the crystalline metastable state to the equilibrium two‐phase state was of the order of 0.12 kJ cm−3 while the activation barrier was ∼19 kJ cm−3. Thus, the metastable alloys, which had average grain sizes of 100–200 nm and a lattice constant which varied linearly with x, exhibited good thermal and temporal stability.
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64.70.K- Solid-solid transitions
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
64.75.-g Phase equilibria
81.15.Cd Deposition by sputtering

Mathematical model for a radioactive marker in silicide formation

C.‐D. Lien and M‐A. Nicolet

J. Appl. Phys. 55, 4187 (1984); http://dx.doi.org/10.1063/1.333037 (7 pages) | Cited 1 time

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A mathematical model is constructed to interpret the profiles of radioactive 31Si tracers in a computer simulation proposed by R. Pretorius and A. P. Botha [Thin Solid Films 91, 99 (1982)]. This model assumes that only Si moves in the silicide, that the Si moves interstitially and convectively, and that the moving Si can exchange sites with the stationary Si in the silicide lattice. An analytical solution of this model is given and confirms the published computer simulation data. However, it is shown that the model is physically inadequate. Solutions of another model which assumes that metal, instead of Si, is the moving species for silicide formation (either interstitially, or substitutionally, or both), with self‐diffusion of 31Si in the silicide during silicide formation. Almost all the experimental data can be fitted by solutions of both models. These examples demonstrate that radioactive tracer experiments alone are insufficient to determine the moving species when a solid binary compound film forms by reaction of adjacent elemental layers. Both inert marker and tracer data are needed to identify the moving species and the mechanisms.
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66.30.Dn Theory of diffusion and ionic conduction in solids
68.55.-a Thin film structure and morphology

A numerical study of manganese redistribution in GaAs employing an interstitial‐substitutional model

A. S. Jordan and G. A. Nikolakopoulou

J. Appl. Phys. 55, 4194 (1984); http://dx.doi.org/10.1063/1.333020 (14 pages) | Cited 5 times

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A finite element simulation of the anomalous out‐diffusion of Mn in GaAs employing an interstitial‐substitutional model combined with defect‐chemical kinetics has been performed. The major species considered were Ga vacancies (VGa ), Mn substitutionals (MnGa), and interstitials (Mni) augmented by shallow donors (DAs ) and Ga vacancy‐donor pairs (VGa‐DAs). Mathematically, the model can be represented by two ordinary differential equations which are the kinetic relations describing the formation of MnGa and VGa‐DAs coupled with three partial differential equations, including sink and source terms, for the diffusion of VGa, Mni, and DAs . The analysis required advanced numerical techniques using dynamic spatial and time meshes. We have achieved a very good theoretical description of Mn out‐diffusion data for both 90 min and 24 h annealing cycles up to a depth of 0.5 μm from the surface [P.B. Klein, P. R. Nordquist, and P. G. Siebenmann, J. Appl. Phys. 51, 4861 (1980)]. Moreover, eventual depletion of the Mn contamination has been demonstrated. However, an inflection beyond 0.5 μm observed in the experimental results cannot be explained by the present treatment.
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66.30.J- Diffusion of impurities
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Formation of thin films of NiSi: Metastable structure, diffusion mechanisms in intermetallic compounds

F. d’Heurle, C. S. Petersson, J. E. E. Baglin, S. J. La Placa, and C. Y. Wong

J. Appl. Phys. 55, 4208 (1984); http://dx.doi.org/10.1063/1.333021 (11 pages) | Cited 114 times

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The formation of NiSi films from the reaction of Ni2Si with (100) and (111) silicon substrates was found to be controlled by a lattice diffusion process with an activation energy of 1.70 eV. In order to correlate kinetic information obtained by Rutherford backscattering with x‐ray diffraction data, ‘‘standard’’ diffraction powder patterns for both Ni2Si and NiSi have been established. The existence of a metastable hexagonal form of NiSi has been confirmed. Observations on the formation of Ni2Si confirm previous investigations. The diffusion process at work during the formation of NiSi is discussed in terms of the crystalline anisotropy of this compound and compared to what is known about diffusion in other silicides.
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66.30.Ny Chemical interdiffusion; diffusion barriers
68.55.-a Thin film structure and morphology
81.10.Jt Growth from solid phases (including multiphase diffusion and recrystallization)
64.60.My Metastable phases

Intermetallic phases formed during tin implantation into iron and steels

P. H. Dionisio, B. A. S. de Barros, and I. J. R. Baumvol

J. Appl. Phys. 55, 4219 (1984); http://dx.doi.org/10.1063/1.333022 (6 pages) | Cited 4 times

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The surface layers of pure iron, high‐carbon steel and stainless steel, ion implanted with 1×1017 Sn+ cm−2, have been characterized by means of 119Sn conversion electrons Mössbauer scattering. The intermetallic phases existent in the as‐implanted samples are determined, and then the thermal decomposition of these phases are established. The phase transformations observed in the treated surfaces agree reasonably well with the phase diagrams reported in the literature for stoichiometric intermetallic phases formed in bulk.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
61.72.U- Doping and impurity implantation
64.70.K- Solid-solid transitions
76.80.+y Mössbauer effect; other γ-ray spectroscopy
79.20.Kz Other electron-impact emission phenomena

Microstructural studies of CdTe and InSb films grown by molecular beam epitaxy

S. Wood, J. Greggi, R. F. C. Farrow, W. J. Takei, F. A. Shirland, and A. J. Noreika

J. Appl. Phys. 55, 4225 (1984); http://dx.doi.org/10.1063/1.333023 (7 pages) | Cited 26 times

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Epitaxial thin films of CdTe (1–5 μm) have been grown directly onto (001) InSb substrates or onto intermediate buffer layers of InSb (0.25–0.5 μm) by molecular beam expitaxy. Cross‐sectional transmission electron microscopy and high‐resolution transmission electron microscopy have been used to characterize the film and interfacial microstructures. Inferences about film quality were also compared with single‐crystal x‐ray rocking curve data and agreed well. Resulting microstructural features were correlated with various experimental growth parameters and substrate cleaning procedures. Results show that near‐perfect CdTe films can be grown on InSb substrates, but film quality is critically dependent upon substrate cleaning. Other factors observed to influence defect formation in the films include growth rate, total growth time, or a change in growth rate during film growth. Extended defects which form include twins, line dislocations, or looplike defects. Lattice imaging has demonstrated the lattice matching across the InSb film/InSb substrate interface, despite the formation of In precipitates during the heat cleaning procedure.
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68.55.-a Thin film structure and morphology
68.60.-p Physical properties of thin films, nonelectronic
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

Deposition parameters and film properties of hydrogenated amorphous silicon prepared by high rate dc planar magnetron reactive sputtering

N. Savvides

J. Appl. Phys. 55, 4232 (1984); http://dx.doi.org/10.1063/1.333024 (7 pages) | Cited 20 times

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The sputtering characteristics for film deposition of hydrogenated amorphous silicon (a‐Si:H) by dc planar magnetron reactive sputtering have been investigated for a range of H2/Ar pressures and applied power. These results indicate that the dc planar magnetron utilizing a silicon target is a high performance sputtering source offering a greater potential for the enlargement of solar cell area and a saving in device‐processing time than other film deposition techniques currently in use. Film properties have been measured as a function of hydrogen partial pressure pH. Results are reported of the room temperature dark conductivity and photoconductivity of films versus pH for pH=0 –0.5 Pa. Films suitable for photovoltaic applications were prepared possessing dark conductivity ≲10−8 Ω−1 cm−1 and photoconductivity ∼10−4 Ω−1 cm−1. The optical absorption coefficient has been determined as a function of photon energy in the range 0.5–6.0 eV. The optical gap was found to increase with pH from 1.7 eV for unhydrogenated material to 2.0 eV for material prepared at pH=3 Pa.
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68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
72.40.+w Photoconduction and photovoltaic effects
84.60.Jt Photoelectric conversion

Relation between growth conditions and reconstruction on InAs during molecular beam epitaxy using an As2 source

Bruce R. Hancock and Herbert Kroemer

J. Appl. Phys. 55, 4239 (1984); http://dx.doi.org/10.1063/1.333025 (5 pages) | Cited 11 times

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We have studied the growth of InAs by molecular beam epitaxy using an As2 source and have determined the growth conditions at which the surface changes from arsenic stable to indium stable. We conclude that the governing parameter is not the flux ratio, but rather the flux difference, i.e., the absolute amount of excess arsenic supplied. We propose a model to explain this behavior.
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68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Ultramicroindentation apparatus for the mechanical characterization of thin films

P. E. Wierenga and A. J. J. Franken

J. Appl. Phys. 55, 4244 (1984); http://dx.doi.org/10.1063/1.333026 (4 pages) | Cited 19 times

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An apparatus is described which is suitable for the mechanical characterization of all kinds of extremely thin films by indentation experiments at very low loads. The penetration depth can be measured as a function of time or load with a resolution of 5 nm. The indentor force can be varied from 10 μN to 5 mN. On the basis of some examples it is demonstrated that the instrument is applicable for ultramicrohardness measurements on metal films as well as for the determination of the viscoelastic properties of polymer coatings. Moreover, it is shown that the apparatus can be used for surface profilometry and ultramicroscratching experiments on relatively soft layers.
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46.80.+j Measurement methods and techniques in continuum mechanics of solids
68.60.-p Physical properties of thin films, nonelectronic
62.20.F- Deformation and plasticity
46.35.+z Viscoelasticity, plasticity, viscoplasticity

Mechanical properties of thin alloy films: Ultramicrohardness and internal stress

A. G. Dirks, J. J. van den Broek, and P. E. Wierenga

J. Appl. Phys. 55, 4248 (1984); http://dx.doi.org/10.1063/1.333027 (9 pages) | Cited 13 times

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On a series of Ag‐Al, Ag‐Au, Ag‐Cu, Au‐Cu, and Au‐Fe thin films, made by vapor deposition, both ultramicrohardness and internal stress were determined as a function of the chemical composition of the deposits. In order to interpret these results microstructural investigations were performed using x‐ray diffraction and transmission electron microscopy, supplemented by electrical resistivity measurements. The observed data on hardness and internal stress can be well understood with the help of the metastable phase diagram of the alloy films. In the case of single‐phase solid solutions, internal stresses are tensile. Compound formation, phase decomposition, or ordering are accompanied with dramatic changes of the internal stresses. With indentation experiments at very low loads the hardness‐concentration dependences were observed in the case of films having a thickness of 1 μm only. Metallic films in general are characterized by a very high defect concentration. Moreover, a dramatic reduction of the average grain size was observed upon alloying. The resulting hardness increase may be understood in terms of a mechanism implying the blocking of the motions of dislocations.
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68.60.-p Physical properties of thin films, nonelectronic

Determination of the minority carrier mobility of n‐type cadmium‐mercury‐telluride using the Haynes–Shockley method

D. E. Lacklison and G. Duggan

J. Appl. Phys. 55, 4257 (1984); http://dx.doi.org/10.1063/1.333028 (9 pages) | Cited 5 times

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The measurement of the minority carrier mobility of n‐type cadmium mercury telluride using Haynes–Shockley method is described. The practical and theoretical aspects of the measurement are presented and compared with the flying light spot method. Observed pulse widths were found to be larger than expected from diffusion broadening alone, a fact which is explained by the existence of an accumulating contact in the vicinity of the minority carrier detection region. The drift velocities determined from the rate of change of delay with distance were found to be relatively insensitive to this pulse distortion. Mobilities of 180 cm2/V s for Cd0.29Hg0.71Te at 185 K and 460 cm2/V s for Cd0.22Hg0.78Te at 90 K have been observed.
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72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Ey III-V and II-VI semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Dynamics of capture from free‐carrier tails in depletion regions and its consequences in junction experiments

E. Meijer, H. G. Grimmeiss, and L‐Å. Ledebo

J. Appl. Phys. 55, 4266 (1984); http://dx.doi.org/10.1063/1.333029 (9 pages) | Cited 33 times

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Exponentially decaying tails of free carriers extend from the neutral material into the depletion region of p‐n junctions or Schottky barriers. In nonequilibrium, deep level impurities in the depletion region may readily capture free carriers from these tails. The strongly nonexponential time dependence of the capture is calculated here and is compared with experimental data. This nonexponential time dependence is particularly important in deep level transient spectroscopy, and it also appears in many other junction measurements with deep level impurities.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Analysis of the electron‐beam‐induced current of a polycrystalline p‐n junction when the diffusion lengths of the material on either side of a grain boundary differ

Oldwig von Roos and Keung L. Luke

J. Appl. Phys. 55, 4275 (1984); http://dx.doi.org/10.1063/1.333030 (5 pages) | Cited 7 times

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The short circuit current generated by the electron beam of a scanning electron microscope in p‐n junctions is reduced by enhanced recombination at grain boundaries in polycrystalline material. Frequently, grain boundaries separate the semiconductor into regions possessing different minority carrier life times. This markedly affects the short circuit current ISC as a function of scanning distance from the grain boundary. It will be shown theoretically that (a) the minimum of the ISC in crossing the grain boundary with the scanning electron beam is shifted away from the grain boundary toward the region with smaller life time (shorter diffusion length), (b) the magnitude of the minimum differs markedly from those calculated under the assumption of equal diffusion lengths on either side of the grain boundary, and (c) the minimum disappears altogether for small surface recombination velocities (s<104 cm/s). These effects become however negligible for large recombination velocities s at grain boundaries. For p‐type silicon this happens for s≥105 cm/s.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
61.72.Mm Grain and twin boundaries
72.80.Cw Elemental semiconductors

Surface conductivity measurements by a capacitive coupling technique

V. Dolgopolov, C. Mazuré, A. Zrenner, and F. Koch

J. Appl. Phys. 55, 4280 (1984); http://dx.doi.org/10.1063/1.333031 (4 pages) | Cited 22 times

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We show how the conductivity of a gate‐voltage‐induced charge layer in a metal‐insulator‐semiconductor (MIS/MOS) capacitor structure can be measured quantitatively without the need for source‐drain contacts. In this scheme, the interface current is driven by an rf voltage applied across a resistive thin‐film gate electrode and coupling capacitively to the conducting interface layer. We give examples that illustrate application possibilities and the sensitivity of the technique.
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73.25.+i Surface conductivity and carrier phenomena
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Effects of surface states and of excitation on barrier heights in a simple model of a grain boundary or a surface

P. T. Landsberg and M. S. Abrahams

J. Appl. Phys. 55, 4284 (1984); http://dx.doi.org/10.1063/1.333038 (10 pages) | Cited 16 times

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The model of a grain boundary (or of a surface) used here employs parallel quasi‐Fermi levels but does not require the depletion approximation. Shockley–Read–Hall recombination via the surface states (including Auger effects) is utilized and the resulting surface trap occupation is displayed as a generalization of the well‐known Fermi–Dirac distribution function. This enables one to cover equilibrium and steady‐state conditions in one treatment. The barrier height has been given as a function of bulk doping, surface energy level density, and also as a function of excitation intensity. The latter is determined by the separation between the quasi‐Fermi levels and can be due to incident light or carrier injection. A number of experimental curves have been fitted satisfactorily on the basis of the theory. Among the conclusions, we note that there is a maximum (with respect to doping) in the barrier height, and that illumination reduces the barrier height. The effect of the energetic position of the surface states is also traced here.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.20.-r Electron states at surfaces and interfaces
73.90.+f Other topics in electronic structure and electrical properties of surfaces, interfaces, thin films, and low-dimensional structures (Restricted to new topics in section 73)

Platinum silicide contacts to silicon by lift‐off

S. S. Cohen, D. H. Bower, D. M. Brown, and J. F. Norton

J. Appl. Phys. 55, 4294 (1984); http://dx.doi.org/10.1063/1.333039 (5 pages)

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Thin layers of platinum silicide, interposed between heavily doped silicon junctions and a thick overlying interconnect metallization, assure that good ohmic contact characteristics prevail. In conventional processes the thin PtSi film is formed by reacting a thin (200–500 Å) sputtered Pt film with the underlying silicon substrate. The unreacted platinum that is found on the surrounding field oxide area is then etched in aqua regia. This self‐aligned process may pose some problems with regard to the integrity of the Pt/Si contact and the device yield. For these reasons we have studied an alternative Pt deposition‐patterning scheme that promises to alleviate the seriousness of these problems. PtSi contacts have been fabricated by means of a new photoresist lift‐off technique. The aim of the present study is to contrast this new lift‐off process for the formation of PtSi contacts to Si with the conventional self‐aligned technique. Our results indicate that the new process is preferred although it gives rise to somewhat higher values for the contact resistance.
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73.40.Cg Contact resistance, contact potential
73.40.Ns Metal-nonmetal contacts
81.05.Bx Metals, semimetals, and alloys
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Interfacial effects due to tunneling to insulator gap states in amorphous carbon on silicon metal‐insulator‐semiconductor structures

A. Azim Khan, John A. Woollam, and Y. Chung

J. Appl. Phys. 55, 4299 (1984); http://dx.doi.org/10.1063/1.333040 (5 pages) | Cited 21 times

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ac conductance and capacitance measurements over the range 10 Hz to 10 MHz for amorphous carbon on silicon metal‐insulator‐semiconductor structures are reported. Data can be interpreted as being due to tunneling of electrons into gap states located in the dielectric. Interface state densities as low as 1.3×1010 eV cm2 are found.
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73.40.Ty Semiconductor-insulator-semiconductor structures
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.25.+i Surface conductivity and carrier phenomena
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Impact ionization induced minority carrier injection by avalanching p‐n junctions

P. A. Childs and W. Eccleston

J. Appl. Phys. 55, 4304 (1984); http://dx.doi.org/10.1063/1.333041 (5 pages) | Cited 1 time

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Excess minority carriers, generated in the substrate of metal oxide semiconductor transistors operating in saturation, are known to present reliability problems in dynamic memory circuits such as random access memories and charge coupled devices. It has been shown that the minority carriers result from light emission associated with the avalanche multiplication region close to the drain. In this paper we report evidence of a new minority carrier injection process which only occurs in p‐n junctions having very low breakdown voltages (≲9 V). The avalanching emitter‐base junctions of bipolar transistors were used as the injection sources and injection efficiencies (defined as the ratio of the minority carrier current to the multiplication current) as high as 5×10−3 were recorded. A model of the injection process based on impact ionization within the neutral regions is proposed. A Monte Carlo simulation of avalanche breakdown is used to demonstrate the feasibility of the model.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Properties of hydrogenated amorphous silicon prepared by chemical vapor deposition

F. B. Ellis, R. G. Gordon, W. Paul, and B. G. Yacobi

J. Appl. Phys. 55, 4309 (1984); http://dx.doi.org/10.1063/1.333042 (9 pages) | Cited 25 times

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Hydrogenated amorphous silicon (a‐Si:H) films were prepared by chemical vapor deposition (CVD) from mixtures of silane, disilane, trisilane, and higher polysilanes in hydrogen carrier gas at 1 atm total pressure, at substrate temperatures from 420–530 °C. Experimental parameters are explained and properties as a function of these parameters are shown. The measurements include hydrogen content (by IR), optical, electrical, and photovoltaic properties of the material. In most respects, the CVD material closely resembles the a‐Si:H usually prepared by glow discharge. The following differences have been noted: (1) the CVD a‐Si:H shows no IR absorption at 840–850 cm−1, which is consistent with the expected better thermal stability of the CVD material because of the much higher substrate temperatures in the CVD process than in the glow discharge process. (2) The band gap of CVD a‐Si:H is lower by about 0.1 eV than glow discharge a‐Si:H of the same hydrogen content. Thus, the band gap of CVD a‐Si:H is better matched to the solar spectrum than is glow discharge a‐Si:H. (3) All three IR absorption bands due to hydrogen are about 20% narrower in the CVD a‐Si:H, suggesting a simpler structure. (4) The temperature dependence of the dark conductivity of CVD a‐Si:H fits a curve for a single activation energy, in contrast to the more complicated temperature dependence often found in glow discharge a‐Si:H, in which two different activation energies are seen at high and low temperatures. This suggests that the conduction mechanism is also simpler in the CVD a‐Si:H. (5) The growth rates of good‐quality CVD films are much higher (up to about 100 Å/s) than are typical of the glow discharge method.
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73.61.Cw Elemental semiconductors
73.61.Ey III-V semiconductors
73.61.Ga II-VI semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
72.40.+w Photoconduction and photovoltaic effects
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
75.20.Ck Nonmetals

High spectral response and photoluminescence of AlxGa1−xAs solar cell structures grown by metalorganic chemical vapor deposition (0.28≤x≤0.53)

M. J. Ludowise and W. T. Dietze

J. Appl. Phys. 55, 4318 (1984); http://dx.doi.org/10.1063/1.333043 (4 pages) | Cited 2 times

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Internal quantum efficiency (spectral response) data are presented for metalorganic chemical vapor deposition‐grown AlxGa1−xAs (0.28≤x≤0.53) solar cell structures. Quantum efficiencies as high as 90% are obtained for x=0.28, falling to ∼45% for x=0.53. Electron diffusion lengths are derived from these data by fitting to theoretical predictions. Photoluminescence data on the samples are also presented showing strong intensity (comparable to GaAs) for 0.28≤x≤0.35. Degradation in performance above x=0.38 is attributed to increased deep level densities and direct‐indirect band‐edge crossover effects.
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73.61.Cw Elemental semiconductors
73.61.Ey III-V semiconductors
73.61.Ga II-VI semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
84.60.Jt Photoelectric conversion
78.40.Fy Semiconductors
72.40.+w Photoconduction and photovoltaic effects

Temperature dependence of the current in SiO2 in the high field tunneling regime

B. Ricco and M. V. Fischetti

J. Appl. Phys. 55, 4322 (1984); http://dx.doi.org/10.1063/1.333044 (8 pages) | Cited 10 times

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In this work, we study the effect of temperature on the tunneling current in thin SiO2 films (≊200 Å) and show that a reversal of behavior is produced by increasing fields. While in the lower range (≤9 MV/cm) the current is well represented by the Fowler–Nordheim model and increases with temperature, it substantially disagrees with the theory at fields close to breakdown (>10 MV/cm) where it is larger than expected and decreases with increasing temperature. This cannot be explained with the formation of (quasi) stable positive charge which is known to be created by high field stress but, under our experimental conditions, is found to be negligibly small. Therefore, we deal with a new kind of effect for which few different possibilities are suggested as mechanisms at the microscopic level.
Show PACS
73.61.Ng Insulators
73.40.Gk Tunneling
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
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