Two-band conduction in TiO2

The contribution of electrons and holes to the electrical conduction of titanium dioxide TiO₂ in the Si/TiO₂/Al structure is determined in experiments on the injection of minority carriers from n-type and p-type silicon layers. It is established that both electrons and holes contribute to electrical conduction of the titanium dioxide layer in the Si/TiO₂/Al structure; i.e., the electrical conduction of titanium dioxide has a two-band nature.     

Temperature-dependent photoluminescence of arsenic-doped Si nanocrystals

The characteristics of temperature-dependent photoluminescence (PL) from Si nanocrystals and effects of arsenic-doping (As-doping) were investigated. The Si nanocrystals on a p-type Si substrate were prepared by low pressure chemical vapor deposition and post-deposition thermal oxidation. The As-doping process was carried out using the gas-phase-doping technique. Temperature-dependent PL from Si nanocrystals exhibited considerable differences between samples with/without As-doping. Phase transition between electron-hole liquid and free exciton was observed in the undoped Si nanocrystals, leading to the increase in PL intensity with temperature less than 50 K. Electron emission from As-doped Si nanocrystals to the p-Si substrate was responsible for the significant increase in PL intensity with temperature greater than 50 K. Characteristics of light emission from Si nanocrystals will facilitate the development of silicon-based nanoscaled light-emitting devices.     

p-Type zinc oxide films grown by infrared-light-assisted pulsed laser deposition

In this paper, ZnO films were grown on sapphire (0001) substrates by infrared-light-assisted pulsed-laser deposition (IRA-PLD). In addition, a nitrogen-plasma-assisted (PA-N) system was utilized for effectively doping the acceptor by radio frequency induction coupled plasma (RF-ICP). The effect of IRA-PLD and PA-N systems was investigated by studying the difference in substrate temperature with and without plasma assistance. We found that ZnO films exhibit no exciton emission with PA-N at a high temperature and that an increase in the substrate temperature yields ZnO films with a (002) and c-axis preferred orientation in a nitrogen (N₂) gas atmosphere. ZnO films are changed from n-type to p-type at a substrate temperature of 673 K by IRA-PLD with an N₂ background atmosphere.     

ESR observation of phosphorus pile-up at the Si/SiO2 interface in boron-doped Si

It is shown that dry thermal oxidation of B-doped (p-type) CZ-grown Si wafers may create P-rich near-interfacial Si layers. Thermal treatments were mostly carried out at T_ox=950±20°C for times 3 ≲ t_ox ≲ 7 h in either a 0.11 MPa high-purity O₂ ambient or strongly-reduced O₂ pressure (p_o2 ≲ 13 mPa). The existence of such layers was discovered by sensitive low T ESR observations, revealing the typical P³¹-in-(n-type) Si spectrum. These measurements in combination with selective etching experiments and number-of-spins determinations showed these surface layers to be actually semiconductor-type reversed. It is argued that the P atoms collected at the Si/SiO₂ interface during thermal treatments are inherently present as bulk impurities in the as-received Si.     

Electrical characterization studies of p-type Ge,Ge1−ySny,and Si0.09Ge0.882Sn0.028 grown on n-Si substrates

The electrical properties of p-type Ge, Ge_1−ySn_y, and Si_0.09Ge_0.882Sn_0.028 samples grown on n-type Si substrates using ultra-high vacuum chemical vapor deposition have been investigated as a function of temperature. Degenerate parallel conducting layers were found in all Ge/Si, Ge_1−ySn_y/Si, and Si_0.09Ge_0.882Sn_0.028/Si samples, which are believed to be associated with dislocation defects at the interface produced by the lattice mismatch between the two materials. These degenerate conducting layers affect the electrical properties of all the thin epitaxial films. Additionally, temperature dependent Hall-effect measurements show that these materials exhibit a conductivity type change from p to n at around 370–435 K. The mobilities of these samples are generally lower than that of bulk Ge due to carrier scattering near the interface between the epitaxial layer and the Si substrate and also due to alloy scattering. Detailed behavior of temperature-dependent conductivity of these samples is also discussed.     

Subharmonic structure of cyclotron resonance an inversion layer on Si

At sufficiently high gate voltages an unexpected, quasi-subharmonic sequence of peaks appears in addition to the usual cyclotron resonance of electrons in an inversion layer on p-type (100) Si. We suggest the effect to be caused by resonance between Landau levels perturbed by negatively charged trap states at the SiSiO₂ interface.     

A first-principles surface phase diagram study for Si-adsorption processes on GaAs(1 1 1)A surfaces

The adsorption processes of an Si atom on GaAs(1 1 1)A surfaces under growth conditions are investigated on the basis of first-principles surface phase diagrams, in which adsorption-desorption behavior is described by comparing the calculated adsorption energy obtained by total-energy electronic-structure calculations with vapor-phase chemical potential estimated by quantum statistical mechanics. The calculated surface phase diagram as functions of temperature and As₂ pressure demonstrates that both Ga and As atoms are adsorbed on the Ga-vacancy site of GaAs(1 1 1)A-(2×2) surface under low As-pressure conditions, resulting in the formation of (2×2) surface with an As adatom. The surface phase diagrams as functions of temperature and Si pressure also reveal that an Si atom can be adsorbed on the (2×2) surface with an As adatom for temperatures less than ∼1160 K and this Si atom can occupy one of As-lattice sites after the incorporation of another As atom, leading to p-type conductivity. In contrast, the (2×2) surface with an As trimer is found to be stabilized under high As-pressure conditions. The surface phase diagram for Si incorporation clarify that an Si atom can be adsorbed at one of Ga-lattice sites of the (2×2) surface with an As trimer for temperatures less than ∼870 K. These calculated results provide one of possible explanations for the formation of p-type and n-type GaAs on GaAs(1 1 1)A surfaces under low and high As-pressure conditions, respectively.     

Room temperature photoluminescence from etched silicon surfaces: The effects of chemical pretreatments and gaseous ambients

The room temperature photoluminescence intensity (RTPLI) from etched Si surfaces is shown to be very sensitive to both the chemical pretreatment and the surrounding ambient. It can be greatly increased by chemical treatments that leave the surface highly n-type or highly p-type, or through effective passivating treatments such as thermal oxidation. The RTPLI from unpassivated, strongly n-type surfaces is severely diminished by oxygen adsorption and from strongly p-type surfaces by water adsorption.Slow RTPLI transients with time constants of the order of minutes are induced by changes in either the intensity of above-band-gap illumination or the gaseous ambient. The transients can exhibit a wide variety of forms and their reversibility is determined by the chemical activity of the illuminated surface, with respect to both adsorption from the surrounding ambient and internal structural changes.The RTPLI is shown to be sensitive to both positive charging of the surface by water vapour and negative charging due to molecular oxygen. Totally reversible transients induced by gaseous cycling under constant illumination are interpreted using the Stevenson-Keyes expression for surface recombination.     

Interference effects in the electrical conductivity tensors of doped polar semiconductors

In this paper, we develop a general procedure, based on the Kubo formula, for finding the frequency- and wavevector-dependent electrical conductivity tensor for arbitrary polarizations of the applied electric field. This procedure gives careful consideration to both the electron and the ion contributions to the current density. We find that, in addition to the standard electron and ion contributions to the conductivity tensor, there are contributions arising from the quantum interference between the electrons and the ions. These interference effects, which will affect the infrared absorption of a material, are similar to the interference effects observed by Cerdeira, Fjeldly, and Cardona (Solid State Commun.13 (1973), 325–328; Phys. Rev. B8 (1973), 4734–4745; 9 (1974), 4344–4350) in Raman scattering from p-type Si. We then evaluate these cross terms for simple models of a variety of semiconductors. We find that these interference effects are finite-q effects, with the actual dependence of the cross terms on the wavevector q being sensitive to the symmetry of the crystal. We also find that, in principle, these cross terms may be quite large near the TO-phonon frequency ω_TO. The cross terms are evaluated for both n-type and p-type semiconductors, and it is suggested that they are probably most important for p-type materials. However, we also find that the basic structure of these terms is very similar in the two cases.     

Interaction between electronic and vibronic Raman scattering in heavily doped silicon

The asymmetry in the one-phonon Raman lines of heavily doped p-type Si is interpreted as the interference of a continuum of electronic excitations with the phonon line. The dependence of the line shape on the exciting frequency is produced by the different resonant behavior of these two scattering mechanisms.     

Auger emission in degenerate GaSb crystals

The dependence of the peak energy of the Auger band on the doping in n-type and p-type degenerate GaSb crystals is investigated, in good agreement with experiments.It is suggested that the continuum for n-type GaSb is only by a factor of 20 stronger than for p-type material, and the maximum value of the stimulated Auger emission in the n-type or p-type GaSb photoluminescence is 4 times weaker than the corresponding maximum value of the near-band-edge emission.     

Two-band conductivity of ZrO<Subscript>2</Subscript> synthesized by molecular beam epitaxy

Using experiments on the injection of minority carriers from n-and p-type silicon, the contribution of electrons and holes to the conductivity of ZrO₂ in the Si/ZrO₂/Al structure is determined. It is found that electrons and holes make a contribution to the conductivity of ZrO₂, so that ZrO₂ exhibits two-band conductivity.     

Self-adjusting formation of a lateral confinement potential in Si/SiGe heterostructures with compensatingpnlayers

We have developed a new concept to create a lateral confinement potential in a two-dimensional electron gas at the interface of a Si/SiGe heterostructure. The method is based on the compensation of then-type doping layer by an additionalp-type layer in a structure similar to a modulation-doped field-effect transistor. A numerical calculation shows that an initially depleted quantum well at zero temperature can be populated by reducing the top-layer thickness. A lateral quantum well is created below a graded step preferentially etched into thep-type layer. Beneath an etched V groove a lateral confinement is obtained with level separation in excess of 8 meV. Similar confinement is achieved in a δ-doped structure with an etch-stop controlled shallow groove.     

Isomer-shift of interstitial and substitutional iron in silicon and germanium

We describe results from in-beam Mössbauer implantation measurements for⁵⁷Fe inn-type Si, inp-type Si, and in Ge. Ab initio calculations for the contact densities from density functional theory in the local-density approximation are presented and their results are employed to locate the type of position of Fe in the lattice of the host. Thus the different spectral features corresponding to interstitial and substitutional Fe in Si and Ge are unambiguously identified.Dedicated to U. Gonser on the occasion of his 70th birthday     

Preparation and characterization of Cd2Nb2O7 thin films on Si substrates

Thin Cd₂Nb₂O₇ films were grown on single-crystal p-type SiO₂/Si substrates by the metallo-organic decomposition (MOD) technique. The films were investigated by X-ray diffraction, X-ray energy-dispersive spectroscopy, and field emission scanning electron microscopy, and showed a single phase (cubic pyrochlore), a crack-free spherical grain structure, and nanoparticles with a mean size of about 68 nm. A Cauchy model was also used in order to obtain the thickness and index of refraction of the stack layers (transparent layer/SiO₂/Si) by spectroscopic ellipsometry (SE). The dielectric constant (K) of the films was calculated to be about 25 from the capacitance-voltage (C-V) measurements.     

Optimization for mid-wavelength InSb infrared focal plane arrays under front-side illumination

The quantum efficiency for mid-wavelength InSb infrared focal plane arrays has been numerically studied by two dimensional simulators. Effects of thickness of p-type layer on the quantum efficiency under front-side illumination have been obtained. The calculated results can be used to extract the optimal thickness of the p-type layer for different absorption and diffusion lengths. It is indicated that the optimal thickness of the p-type layer strongly depends on the absorption coefficient and the minority carrier lifetimes. The empirical formulas are also obtained to describe the correlation between the optimal thickness of the p-type layer, and the absorption and diffusion lengths.     

States of hydrogen in crystalline semiconductors

Abstract

The stable configurations of hydrogen in undoped, and in n- and p-semiconductors are reviewed. We compare the experimentally determined configurations with theoretical predictions made by a variety of calculational methods. In undoped Si, as an example, hydrogen appears to occupy a energy occurring at a tetrahedral interstitial (T) site. In B-doped, p-type Si, hydrogen at a near BC site accounts for acceptor passivation. By contrast in n-type Si, hydrogen at the antibonding (AB) position appears to be responsible for donor passivation. The possible configurations in other semiconductors (Ge, GaAs and AlGaAs) are also summarized.     

Self-consistent numerical solutions of p-type inversion layers in silicon mos devices

We present a self-consistent numerical calculation to study the energy of the subbands of holes on p-type inversion layers in silicon MOS devices. The variation of the masses with the concentration of carriers is considered self-consistently, taking into account the non-parabolicity and anisotropy of the valence band. These properties are mandatory on the behaviour of the excited states giving opposite trends for p-type and n-type channels.     

Formation of p-type ZnMgO thin films by In-N codoping method

In-N codoped ZnMgO films have been prepared on glass substrates by direct current reactive magnetron sputtering. The p-type conduction could be obtained in ZnMgO films by adjusting the N₂O partial pressures. The lowest resistivity was found to be 4.6 Ω cm for the p-type ZnMgO film deposited under an optimized N₂O partial pressure of 2.3 mTorr, with a Hall mobility of 1.4 cm²/V s and a hole concentration of 9.6 × 10¹⁷ cm⁻³ at room temperature. The films were of good crystal quality with a high c-axis orientation of wurtzite ZnO structure. The presence of In-N bonds was identified by X-ray photoelectron spectroscopy, which may enhance the nitrogen incorporation and respond for the realization of good p-type behavior in In-N codoped ZnMgO films. Furthermore, the ZnMgO-based p-n homojunction was fabricated by deposition of an In-doped n-type ZnMgO layer on an In-N codoped p-type ZnMgO layer. The p-n homostructural diode exhibits electrical rectification behavior of a typical p-n junction.     

Influence of screening on deformation potential and piezoelectric scattering in doped semiconductors

Mobility relations are derived for deformation potential and piezoelectric scattering accounting for the screening by free charge carriers. Estimations of the screening influence on the carrier mobility in n-type GaN and p-type GaAs are made. It is shown that particularly in p-type GaAs the screening effect cannot be neglected in analysing the hole mobility even at high carrier concentrations.