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15 Feb 1986

Volume 59, Issue 4, pp. R1-1404

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Hydrogen impurities in quantum well wires

Jerry W. Brown and Harold N. Spector

J. Appl. Phys. 59, 1179 (1986); http://dx.doi.org/10.1063/1.336555 (8 pages) | Cited 124 times

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The binding energy of hydrogenic impurites in a quantum well wire has been calculated as a function of the width of the quantum well wire and the location of the impurity with respect to the axis of the wire. The calculations have been preformed using a variational wave function which takes into account the confinement of the carriers in the wire. For the confining potential used in our calculations, we have used the models of either an infinite potential well or a finite potential well whose depth is detemined by the discontinuity of the band gas in the quantum well wire and the cladding. For the infinite potential well model, the binding energy continues to increase as the radius of the wire decreases while in the finite potential well model, the binding energy reaches a peak value as the wire radius decreases and then decreases to a value characteristic of the cladding. The binding energy also depends upon the location of the impurity in the wire and is a maximum when the impurity is located on the axis of the wire.
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78.40.Fy Semiconductors
78.30.-j Infrared and Raman spectra

Leaky surface polariton

S. R. Seshadri

J. Appl. Phys. 59, 1187 (1986); http://dx.doi.org/10.1063/1.336556 (9 pages) | Cited 13 times

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The characteristics of a leaky surface polariton existing on the surface of a free electron metal having the profile of an ordinary diffraction grating are investigated including the effects of the finite length of the grating and the slow spatial variation of the amplitude of the surface polariton. The radiative decay characteristics of the surface polariton and the characteristics of the antiresonance in the angular response of the reflectivity of light incident on the grating are discussed, and the effect of a small dissipation in the metal on these characteristics is also included.
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42.79.Dj Gratings
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
84.40.Ba Antennas: theory, components and accessories
78.90.+t Other topics in optical properties, condensed matter spectroscopy and other interactions of particles and radiation with condensed matter (restricted to new topics in section 78)

Photoionization thresholds of rare‐earth impurity ions. Eu2+:CaF2, Ce3+:YAG, and Sm2+:CaF2

C. Pedrini, F. Rogemond, and D. S. McClure

J. Appl. Phys. 59, 1196 (1986); http://dx.doi.org/10.1063/1.336557 (6 pages) | Cited 74 times

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The spectral dependence of the photoionization energy of Eu2+:CaF2, Ce3+:YAG, and Sm2+:CaF2 systems have been measured and thresholds experimentally determined and compared with theoretical values calculated from electrostatic models. It is shown that the excited state absorption transitions or the persistent hole burning observed by other authors occur above the threshold energy of photoionization of the impurities and that the states of the crystal which form the bottom of the conduction band may play an important role in the strong probability of these processes. A review of thresholds now known is also given.
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78.40.Fy Semiconductors
72.40.+w Photoconduction and photovoltaic effects
78.30.Hv Other nonmetallic inorganics
78.40.Ha Other nonmetallic inorganics

Neodymium complexes in GaP separated by photoluminescence excitation spectroscopy

J. Wagner, H. Ennen, and H. D. Müller

J. Appl. Phys. 59, 1202 (1986); http://dx.doi.org/10.1063/1.336558 (3 pages) | Cited 23 times

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Implantation of neodymium (Nd) in GaP gives rise to a very complex spectrum of intra 4f‐shell luminescence transitions involving a number of Nd defect associates. Using a tunable color center laser, photoluminescence excitation spectroscopy was employed to separate different Nd3+ complexes in GaP:Nd. Two dominant noncubic Nd centers are clearly identified which arise presumably from the association of Nd with radiation damage centers.
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78.40.Fy Semiconductors
78.30.-j Infrared and Raman spectra
61.72.U- Doping and impurity implantation

Electrical properties of shallow levels in p‐type HgCdTe

E. Finkman and Y. Nemirovsky

J. Appl. Phys. 59, 1205 (1986); http://dx.doi.org/10.1063/1.336506 (7 pages) | Cited 33 times

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Electrical measurements of gold‐doped and undoped p‐type Hg1−xCdxTe with x≂0.22 are reported and two models based on two shallow acceptor levels for the analysis of the Hall data are developed. One model assumes two independent acceptors and the other assumes one divalent acceptor. The models yield ionization energies of 12.5±2 and 2–5 meV. The concentration of the compensating donors is of the order of the hole concentration. Arguments are given in order to assign these levels to established point defects.
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78.40.Fy Semiconductors
72.80.Ey III-V and II-VI semiconductors
72.20.My Galvanomagnetic and other magnetotransport effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Diffusion coefficient of holes in silicon by Monte Carlo simulation

Lino Reggiani, Rossella Brunetti, and Edmundas Normantas

J. Appl. Phys. 59, 1212 (1986); http://dx.doi.org/10.1063/1.336507 (4 pages) | Cited 14 times

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A theoretical investigation of the diffusivity of holes in Si as a function of temperature, field strength, and field direction is reported. Calculations have been performed with the Monte Carlo procedure. The theoretical analysis explains the main features exhibited by the experimental data available from the literature. Minor discrepancies between theory and experiment are discussed in terms of microscopic mechanisms and/or reliability of the different experimental techniques used.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.20.Ht High-field and nonlinear effects
72.20.Dp General theory, scattering mechanisms
71.20.Mq Elemental semiconductors

Calibrated mapping of the electrical activity in deformed silicon by means of charge‐collection microscopy

L. W. Snyman, H. C. Snyman, and J. A. A. Engelbrecht

J. Appl. Phys. 59, 1216 (1986); http://dx.doi.org/10.1063/1.336508 (4 pages) | Cited 3 times

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A method has been developed to obtain, by means of charge‐collection microscopy (CCM), a calibrated two‐dimensional map of the electrical activity of the minority carriers in a semiconductor crystal over large crystal dimensions. This is achieved by the calibration of the collection current in terms of the minority‐carrier diffusion length and a photographic gray scale. The technique is applied to plastically deformed silicon and proves that it has great potential for the evaluation of electrical activity mechanisms in imperfect silicon.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Cw Elemental semiconductors

A theoretical analysis of electron transport in ZnSe

H. E. Ruda

J. Appl. Phys. 59, 1220 (1986); http://dx.doi.org/10.1063/1.336509 (12 pages) | Cited 27 times

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Boltzmann’s transport equation was solved using a variational method (including all major scattering mechanisms and screening) yielding electron mobilities in n‐ZnSe. The electron concentration dependence of the mobility at 300 and 77 K was calculated as functions of ionized impurity concentration and compensation ratio. A routine method for determining acceptor and donor densities (total and ionized) and compensation ratio from given experimental mobility and carrier concentration values is outlined; mobilities reported for samples grown by various techniques are discussed. Inherent limits to the mobility are given as about 800 cm2/V s (n∼3×1018 cm−3) and about 1×104 cm2/V s (n≤4×1015 cm−3) at 300 and 77 K, respectively. The calculated temperature dependence of the mobility for η=−6 is used to explain qualitative trends in such behavior for material grown by different techniques, and to provide an inherent mobility limit at this η.
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72.20.Dp General theory, scattering mechanisms
72.20.Fr Low-field transport and mobility; piezoresistance
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Ey III-V and II-VI semiconductors

Penetration depths of low‐energy hydrogen‐ion implantation on ZnO surfaces

G. Yaron, J. Levy, Y. Goldstein, and A. Many

J. Appl. Phys. 59, 1232 (1986); http://dx.doi.org/10.1063/1.336510 (6 pages) | Cited 9 times

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The penetration depths of protons in the (0001) face of ZnO produced by 100‐ and 400‐eV hydrogen‐ion bombardment are studied by three methods: calibrated argon‐ion sputtering, calibrated etching, and space‐charge capacitance measurements in the ZnO/electrolyte system. For the 100‐eV implantation, the latter method provides unequivocal support to our previous conclusion that the protons, acting as fully ionized donors, penetrate only to a depth of 10–20 Å below the surface. The narrow space‐charge layer so produced, having surface electron densities of up to 2 × 1014 cm−2, constitutes a quantized, two‐dimensional electron gas system. In the 400‐eV implanted surface, the proton penetration depth is considerably larger. In this case an approximate depth profile could be derived from the combined measurements. It consists of a Gaussian distribution, peaked about 40 Å below the surface with a standard deviation of some 80 Å. However, some 10% of the implanted protons are found to penetrate much deeper, being distributed up to 1000 Å or more below the surface. For 100‐eV implanted surfaces, similarly large penetration depths were observed, but the percentage of the deep lying protons is less than 1%. Such huge penetration depths arise most probably from a channeling mechanism.
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61.72.U- Doping and impurity implantation
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
73.30.+y Surface double layers, Schottky barriers, and work functions

Low‐frequency admittance measurements on the HgCdTe/Photox SiO2 interface

G. H. Tsau, A. Sher, M. Madou, J. A. Wilson, V. A. Cotton, and C. E. Jones

J. Appl. Phys. 59, 1238 (1986); http://dx.doi.org/10.1063/1.336511 (7 pages) | Cited 5 times

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The complex admittance of an n‐type Hg1−xCdxTe/Photox SiO2 interface with x=0.3 has been examined for frequencies ranging between 1 mHz and 4 MHz. The conductance method is used to decompose the total interface state density into three types of components: a valence‐band tail, a conduction‐band tail, and some well‐resolved discrete states. The fixed charge density is low and there is no statistical broadening. The surface valence‐ and conduction‐band edges are both found to be shifted upward in energy relative to their respective bulk values; moreover, the surface has converted to p type. The energy variation of the valence‐band tail states response times follows a pattern characteristic of Shockley–Read recombination centers with a constant capture cross section, but the behavior of the conduction‐band tail states is more complicated. Evidence is presented that the interface region has a higher Cd concentration than the bulk.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Photoelectric study of the Ni‐ and Ni‐TeO2‐electrodeposited n‐type CdTe interfaces

S. M. So, W. Hwang, P. V. Meyers, and C. H. Liu

J. Appl. Phys. 59, 1245 (1986); http://dx.doi.org/10.1063/1.336512 (6 pages) | Cited 3 times

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The barrier heights of the electrodeposited n‐type CdTe thin‐film metal semiconductor (MS) and metal‐thin insulating layer‐semiconductor (MIS) devices have been measured by internal photoemission. The data for both MS and MIS devices can be fit with the square root of the photocurrent per absorbed photon dependence consistent with the Fowler theory. The barrier height of Ni‐CdTe is 0.75 eV at room temperature, and its temperature dependence is about the same as that of the CdTe band gap. This suggests that the barrier height is pinned with respect to the CdTe valence band edge. Oxidation in air at 300 °C for an hour produces a layer of about 25 Å or TeO2 on the CdTe surface. Thicker oxide can be grown for longer oxidation time. Negative oxide charges are found in some devices. At room temperature, the barrier height of Ni‐TeO2‐CdTe is 0.92 eV. As temperature is decreased, the barrier height increases and its rate of change with temperature is less than that of the CdTe band gap. Samples stored in room atmosphere show aging effects, one of which is the increase in surface‐state density. The dips in the curve of the spectral dependence of the relative photon‐induced current are caused by electrons which drift to the metal after being photoexcited from occupied surface states below the Fermi level. These dips correspond to peaks in the energy distribution of the surface state density. At zero bias and 170 °K, four peaks at 1.02, 1.06, 1.18, and 1.26 eV are observed for the MIS devices. For the MS devices zero biased at room temperature, four peaks at 0.85, 0.94, 1.02, and 1.05 eV are observed. The magnitudes of the dips at 0.85, 0.94, 1.18, and 1.26 eV vary with bulk‐defect density and these levels shift towards higher energy as temperature is decreased. On the other hand, the levels at 1.02 and 1.05 eV for the MS devices and 1.02 and 1.06 eV for the MIS devices are independent of temperature and bulk defect density.
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73.40.Ns Metal-nonmetal contacts
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
84.60.Jt Photoelectric conversion
72.40.+w Photoconduction and photovoltaic effects

The electronic properties of plasma‐deposited films of hydrogenated amorphous SiNx (0<x<1.2)

A. J. Lowe, M. J. Powell, and S. R. Elliott

J. Appl. Phys. 59, 1251 (1986); http://dx.doi.org/10.1063/1.336513 (8 pages) | Cited 59 times

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We present the results of a comprehensive series of measurements on glow‐discharge (plasma) ‐deposited silicon nitride films SiNx:H, with x in the range 0<x<1.2. Optical spectroscopy in the visible and infrared regions is used to investigate the nature of the bonding and to assess the role of hydrogen. With increasing x, in the range x<0.7, an increase in the concentration of Si‐H bonds results in an increase in the total hydrogen content; at higher x the rise in the N‐H concentration produces a small increase in the hydrogen content, but even for these samples most of the hydrogen is bonded to silicon. The optical absorption edge due to band‐gap transitions broadens with increasing x due to a change in the nature of the valence band from Si‐Si bonds to N lone‐pair states. Electrical conductivity at high fields and magnetic resonance measurements give information about the defects in the band gap. These results support the Robertson–Powell model in which the principal defect in the band gap of silicon nitride is the silicon dangling bond.
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73.61.Ng Insulators
75.20.Ck Nonmetals
71.55.Jv Disordered structures; amorphous and glassy solids

Deposition and properties of zinc telluride and cadmium zinc telluride films

T. L. Chu, Shirley S. Chu, F. Firszt, and Chuck Herrington

J. Appl. Phys. 59, 1259 (1986); http://dx.doi.org/10.1063/1.336514 (5 pages) | Cited 10 times

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Thin films of ZnTe and Cd1−xZnxTe (x<0.5) have been deposited by the direct combination of the elements on the surface of W/graphite, ceramic, and glass substrates at 550–600 °C in a hydrogen or helium atmosphere. Their microstructure, crystallographic, optical, and electrical properties were studied. Because of the greater stability of ZnTe than CdTe, the Zn/Cd molar ratio in Cd1−xZnxTe films is always less than that in the gas phase. The optical band gap of ZnTe has been determined to be 2.25 eV and that of Cd1−xZnxTe is a linear function of the composition. Preliminary work on Cd1−xZnxTe /CdS heterojunctions has also been carried out.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
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
75.20.Ck Nonmetals
68.55.-a Thin film structure and morphology

Relaxation of optically induced inversion layers in metal‐insulator‐semiconductor tunnel diodes

Walter E. Dahlke and Sanjay Jain

J. Appl. Phys. 59, 1264 (1986); http://dx.doi.org/10.1063/1.336515 (8 pages) | Cited 1 time

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Transient capacity measurements between 77 and 300 K were performed to study the relaxation of optically induced inversion layers in metal‐insulator‐n silicon structures with 23–176‐Å oxide thickness. The observed fluence of the charge in interface and inversion layer exhibits as a function of time three distinct maxima. A theoretical study of the two governing nonlinear differential equations—Shockley–Read–Hall recombination in interface traps, and continuity equation for holes in the valence band—shows that the first peak is caused by recombination in silicon‐bulk traps while the second and third peaks are generated by tunneling recombination in interface traps. A quantitative analysis of the data shows satisfactory agreement between experiment and theory.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Gk Tunneling
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Magnetic measurements on Pr (BrO3)3 ⋅ 9H2O single crystal and a study of the effects and origin of the crystal field

D. Neogy, T. Purohit, and A. Chatterji

J. Appl. Phys. 59, 1272 (1986); http://dx.doi.org/10.1063/1.336516 (6 pages) | Cited 10 times

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Praseodymium bromate was prepared from Pr2O3 and the single crystals of Pr (BrO3)3 ⋅  9H2O were grown. The principal magnetic susceptibility χ⊥ and the anisotropy χ∥‐χ⊥ was measured in the range 300–90 K. The variation of the average magnetic moment peff with temperature is appreciable showing a deviation from the Curie law. The magnetic anistropy χ∥‐χ⊥ is found to be much higher than in Pr‐ethylsulfate where the Pr3+ ion occupies a site very similar to that in PrBR. A crystal field analysis with a field of D3h symmetry is found to provide an excellent account of the magnetic properties observed by us and Simizu et al. [J. Appl. Phys. 55, 2333 (1984)] from 300 K down to ∼0.06 K. The Hamiltonian was diagonalized in the complete basis of the 3H ground term taking care of the intermediate coupling effects to a large extent. Some important predictions on the electronic heat capacity and the electric quadrupole splitting have been made. An estimate of the crystal field parameters has been made using the available structural data on the crystal and the results are discussed in the light of our phenomenological set of parameters.
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75.30.Cr Saturation moments and magnetic susceptibilities
75.30.Gw Magnetic anisotropy
75.10.Dg Crystal-field theory and spin Hamiltonians
65.40.-b Thermal properties of crystalline solids
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems

Thermal domain drag effect in amorphous ferromagnetic materials. I. Theory

S. U. Jen and L. Berger

J. Appl. Phys. 59, 1278 (1986); http://dx.doi.org/10.1063/1.336517 (7 pages) | Cited 7 times

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A steady, collective translation of domain walls has been detected through direct wall observations in metallic ferromagnets subjected to a constant temperature gradient. A 60‐Hz ac external field HE is used to reduce the effect of pinning forces on the walls. Three driving mechanisms, Nernst–Ettinghausen mechanism, end‐drive mechanism, and isothermal end‐drive mechanism, are proposed. Three pinning mechanisms, bulk pinning, surface pinning, and end pinning are believed to be effective in these materials. The region in the (dT/dx,H0E) plane corresponding to static walls has a triangular shape. We have generalized the theory to include the three pinning wells, and the corresponding theoretical phase diagrams are shown. The saturation of phase boundary is also discussed.
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75.60.Ch Domain walls and domain structure
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
81.40.Rs Electrical and magnetic properties related to treatment conditions

Thermal domain drag effect in amorphous ferromagnetic materials. II. Experiments

S. U. Jen and L. Berger

J. Appl. Phys. 59, 1285 (1986); http://dx.doi.org/10.1063/1.336518 (6 pages) | Cited 2 times

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Ferromagnetic domain walls are observed to move from the hot to the cold end of samples of amorphous (Co92.5Fe7.5)78Mo2B15Si5 subjected to a constant temperature gradient dT/dx. An ac magnetic field H0E parallel to the easy axis is used to decrease pinning forces on the walls. The critical temperature gradient (dT/dx)c required to move walls is of order 102 K/mm. The linear decrease of (dT/dx)c with increasing H0E indicates that pinning of the walls by the two ends of the sample is dominant over bulk pinning. The dependence of (dT/dx)c on sample length and thickness indicates that the Nernst–Ettingshausen drive mechanism is dominant over competing drive mechanisms. The speed of walls has been measured and is found to increase with increasing temperature gradient.
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75.60.Ch Domain walls and domain structure
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
81.40.Rs Electrical and magnetic properties related to treatment conditions

Effect of oxidation on the magnetic properties of unprotected TbFe thin films

R. B. van Dover, E. M. Gyorgy, R. P. Frankenthal, M. Hong, and D. J. Siconolfi

J. Appl. Phys. 59, 1291 (1986); http://dx.doi.org/10.1063/1.336519 (6 pages) | Cited 38 times

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Amorphous Tb‐Fe thin films prepared by dual magnetron cosputtering were exposed to air at 200 °C in order to investigate the evolution of the films as they oxidize. Magnetic properties of the films were measured using a vibrating‐sample magnetometer and torque magnetometer and are interpreted in light of the structure of the films as revealed by Auger electron spectroscopy and composition‐depth profiling. This leads to a detailed and self‐consistent description of the oxidation process. At first a uniform and homogeneous oxidation layer grows from the surface toward the substrate. This layer has a high magnetization and low intrinsic anisotropy and consists of an intimate mixture of oxidized Tb and metallic TbxFe(1−x). The initially high intrinsic anisotropy of the unoxidized region decreases relatively quickly, while the composition changes only slowly as this region shrinks. When the oxidation layer reaches the substrate, two oxide phases (Fe2O3 and Tb2O3) begin to grow at the surface exposed to air.
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81.05.Bx Metals, semimetals, and alloys
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.70.-i Magnetic properties of thin films, surfaces, and interfaces
75.30.-m Intrinsic properties of magnetically ordered materials

(FeCo)‐Nd‐B permanent magnets by liquid dynamic compaction

T. S. Chin, Y. Hara, E. J. Lavernia, R. C. O’Handley, and N. J. Grant

J. Appl. Phys. 59, 1297 (1986); http://dx.doi.org/10.1063/1.336520 (4 pages) | Cited 12 times

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A new rapid solidification processing technique, liquid dynamic compaction (LDC), has been used to make bulk permanent magnets of composition Fe57 Co20 Nd15 B8. In this process, molten metal is spray atomized onto a cooled substrate in a protective atmosphere. Oxidation is minimal. Subsequent heat treatment at 450 °C of the LDC’d material has resulted in isotropic permanent magnets with intrinsic coercivity and remanance approaching 8000 Oe and 6000 G, respectively.
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81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.40.Rs Electrical and magnetic properties related to treatment conditions
07.55.Db Generation of magnetic fields; magnets
85.70.-w Magnetic devices
75.50.Kj Amorphous and quasicrystalline magnetic materials

Surface waves in thin‐film coatings on piezoelectric half‐space and on piezoelectric plate belonging to the (622) crystal class

P. Vivekanandaa and V. R. Srinivasamoorthy

J. Appl. Phys. 59, 1301 (1986); http://dx.doi.org/10.1063/1.336521 (4 pages) | Cited 3 times

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Love‐type surface waves in thin‐film coatings on a piezoelectric half‐space of the (622) crystal class are studied. Silver and gold coatings are used on the piezoelectric half‐space, and numerical results are obtained for the relationship between the velocity and the wave number. Surface waves by thin‐film coatings on both sides of an infinite piezoelectric plate of the (622) crystal class are also studied. The dispersion equation has been solved for a given velocity to obtain the wave number numerically.
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68.35.Ja Surface and interface dynamics and vibrations
41.20.Jb Electromagnetic wave propagation; radiowave propagation
77.65.-j Piezoelectricity and electromechanical effects
68.60.Bs Mechanical and acoustical properties

Photoluminescence from heavily doped Si layers grown by liquid‐phase epitaxy

J. Wagner, W. Appel, and M. Warth

J. Appl. Phys. 59, 1305 (1986); http://dx.doi.org/10.1063/1.336522 (4 pages) | Cited 1 time

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Heavily phosphorus or gallium‐doped silicon was grown by liquid‐phase epitaxy and studied by photoluminescence. For the phosphorus‐doped samples grown from In(P) solution, recombination of free electrons to compensating In acceptor levels was observed besides the free electron‐free hole band‐to‐band emission. The gallium‐doped samples showed a luminescence spectrum similar to the one observed in bulk‐doped p‐type material, indicating a good crystalline quality and low compensation in these samples. The band‐gap shrinkage was found to be larger in heavily gallium‐doped than in boron‐doped silicon, indicating a dependence of this shrinkage on the chemical nature of the dopant atoms.
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78.40.Fy Semiconductors
71.20.Mq Elemental semiconductors

A tunneling theory of exciton photoluminescence for neutral acceptors in silicon: A study of the systems Si: (B, In), Si: (Al, In), Si: (Ga, In), Si: (B, Al), Si: (B, Ga), and Si: (Al, Ga)

David S. Moroi, Melvin C. Ohmer, Frank Szmulowicz, and David H. Brown

J. Appl. Phys. 59, 1309 (1986); http://dx.doi.org/10.1063/1.336523 (7 pages) | Cited 8 times

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Rate equations for the densities of free excitons and excitons bound to two different neutral acceptors in silicon are solved for steady state in the absence of saturation. These rate equations explicitly include terms for forward and reverse tunneling of bound excitons from one type of neutral impurity to another. Both tunneling rates are calculated using a simple model of an exciton in a one‐dimensional semi‐infinite double potential well. The steady‐state solutions of the rate equations yield an expression for the ratio of the bound exciton luminescence intensity as a function of the impurity concentrations. The relative photoluminescence intensities for the systems Si: (B, In), Si: (Al, In), Si: (Ga, In), Si: (B, Al), Si: (B, Ga), and Si: (Al, Ga) are calculated for the relevant free‐exciton capture cross‐section ratios. This model predicts no exciton tunneling for any of the above systems for the low‐impurity concentration range of 1012–1013 cm−3. For those systems with large differences in the bound exciton energy levels such as Si: (B, In), Si: (Al, In), and Si: (Ga, In), and having indium concentrations exceeding 1015 cm−3, it predicts quenching of shallow impurity bound exciton luminescence because the forward exciton tunneling rate from the shallow level to the deep level of indium dominates and the reverse exciton tunneling rate from indium to the shallow impurities is negligible. For the systems with small differences in the bound exciton energy levels such as Si: (B, Al) and Si: (B, Ga), the theory predicts enhancement of shallow impurity bound exciton luminescence beyond certain concentrations depending upon the free‐exciton capture cross‐section ratios because in these cases the reverse exciton tunneling rate dominates. For the system Si: (Al, Ga) in which the difference in the bound exciton energy levels is very small, gallium bound exciton luminescence dominates when the gallium concentration exceeds 1016 cm−3.
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78.40.Fy Semiconductors
71.35.-y Excitons and related phenomena
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients

Two‐beam photoacoustic phase measurement of the thermal diffusivity of solids

O. Pessoa, C. L. Cesar, N. A. Patel, H. Vargas, C. C. Ghizoni, and L. C. M. Miranda

J. Appl. Phys. 59, 1316 (1986); http://dx.doi.org/10.1063/1.336524 (3 pages) | Cited 99 times

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A simple method is demonstrated for obtaining the thermal diffusivity of solids, by measuring the phase lag between a front and rear illumination, at a single chopping frequency. The method is tested using some semiconductor and glass samples.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
44.30.+v Heat flow in porous media
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects

Deposition and photoconductivity of hydrogenated amorphous silicon films by the pyrolysis of disilane

T. L. Chu, Shirley S. Chu, S. T. Ang, D. H. Lo, A. Duong, and C. G. Hwang

J. Appl. Phys. 59, 1319 (1986); http://dx.doi.org/10.1063/1.336525 (4 pages) | Cited 13 times

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The thermal decomposition of disilane (Si2H6) in a hydrogen or helium flow has been used for the deposition of hydrogenated amorphous‐silicon (a‐Si:H) films on the surface of Corning 7059 glass substrates at 450–500 °C. The reaction product consists of monosilane and trisilane in addition to the unreacted disilane and ethylsilane (the major impurity in commercial disilane). The concentration of Si2H6 in the reaction mixture has been found to strongly affect the deposition rate and the photoconductivity of a‐Si:H films. At a given Si2H6 concentration, the deposition rate of a‐Si:H films increases exponentially with temperature. At a given substrate temperature, the AM1 conductivity of a‐Si:H films increases with increasing Si2H6 concentration and approaches 10−5 Ω cm−1 at Si2H6 concentrations higher than about 4%, and the conductivity ratio in better films is about 105. The conductivities of CVD a‐Si:H films have been found to show negligible change under illumination over a period of several days. The optical band gap of a‐Si:H films has been determined to be 1.65–1.68 eV. The doping of a‐Si:H films with arsenic and boron has been carried out, and their activation energies determined.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
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
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Nonlinear optical studies and CO2 laser‐induced melting of Zn‐doped GaAs

R. B. James, W. H. Christie, R. E. Eby, B. E. Mills, and L. S. Darken

J. Appl. Phys. 59, 1323 (1986); http://dx.doi.org/10.1063/1.336526 (11 pages) | Cited 3 times

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The absorption of CO2 laser radiation in p‐type GaAs is dominated by direct free‐hole transitions between states in the heavy‐ and light‐hole bands. For laser intensities on the order of 10 MW/cm2, we report that the absorption associated with these transitions in moderately Zn‐doped GaAs (∼1017 cm−3) begins to saturate in a manner predicted by an inhomogeneously broadened two‐level model. At higher laser intensities surface melting occurs initially at localized sites in moderately doped material and more uniformly in heavily Zn‐doped samples (≳1018 cm−3). As the energy density of the CO2 laser radiation is progressively increased further, the surface topography of the samples shows signs of ripple patterns, high local stress, vaporization of material, and exfoliation of solid GaAs fragments. Electron‐induced x‐ray emission data taken on the laser‐melted samples show that there is a loss of As, compared to Ga, from the surface during the high‐temperature cycling. By irradiating the samples in air, argon, and vacuum, we find that the vaporization rates are directly influenced by the ambient environment, particularly by the interaction of oxygen with the molten GaAs. Secondary ion mass spectrometry measurements are used to study the diffusion of oxygen from the native oxide and the incorporation of oxygen in the near‐surface region of the GaAs samples that have been melted by a CO2 laser pulse. We find that oxygen incorporation does occur, and that the amount and depth of the oxygen incorporation depends on the laser energy density, number of laser shots, and ambient environment. For samples that are irradiated in argon or vacuum, we find that removal of the native oxide can be accomplished with CO2 laser pulses. Similar measurements are performed on Si‐implanted GaAs, and results are reported for the redistribution of the implanted silicon atoms, the deviations from stoichiometry, and the incorporation of oxygen in the resolidified layer.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties
81.65.-b Surface treatments
68.35.B- Structure of clean surfaces (and surface reconstruction)
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