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A quasi-3D simulation for quantum well (QW) distributed feedback (DFB) laser diodes is presented. It takes into account both longitudinal effects such as the nonuniformity of the optical intensity, local gain, and spontaneous emission, and lateral effects such as current spreading, quantum carrier capture, and quantum carrier heating. The simulation is performed by solving several 2D cross-sections using Minilase II and a 1D longitudinal solver in a self-consistent fashion. As an example, an analysis of spatial hole burning in a λ/4 phase shifted DFB laser is given. It is shown that spatial hole burning (SHB) results in a local gain saturation, and is mainly restricted to electrons and holes within the QW. Investigations of electron heating at high power show that the temperature distribution of the bound electrons and the LO phonons in the QW is insignificant, and only slightly influenced by SHB.

We present a perturbative method of calculating the temperature-dependent correction, Delta G, to the Landauer conductance which is due to the inelastic electron-phonon scattering. The limits of applicability of these methods as well as the critical interval of temperature (and other relevant parameters) on which the transition from the ballistic transport to the Boltzmann-Drude transport occurs are discussed.

A general technique is developed to account for the microscale heat transfer effects involved with the interaction of thermal radiation and multilayer thin films. In particular, the microscale radiation effects involved with both the emission from the multilayer structure and the reflection of incident radiation are described in detail. Considerable optical interference within the structure occurs when the film thicknesses are on the same order of magnitude as the wavelengths of the incident or emitted radiation; therefore, the net surface reflectivity and emission from the film structure are altered by slight changes in film thickness. Consequently, during high temperature thermal processing of micron thickness films, the resultant temperature profiles and the quality of the processed structure will be affected. The reflectivities and emissivities are calculated numerically using the matrix method for several different layering structures subject to thermal radiation. For the special case of equal optical film thicknesses, cross-correlation peaks are identified; these layering schemes are very sensitive to small film thickness changes. Maximum temperatures attained during thermal processing are calculated for several specific film structures to illustrate the significance of these effects.

Using a first‐principles approach to the ionization rate, we re‐examine some of the prejudices concerning impact ionization and offer a new view of the role of thresholds. We also discuss trends of ionization coefficients related to the energy band structure for silicon and a number of III‐V compounds.

Thermal processing of semiconductive multilayer thin film structures is used extensively for material quality enhancement. The quality of the resultant material is highly dependent on the heat transfer dynamics of the process. Although trial and error techniques are still used for process parameter optimization, efforts have been made to understand the fundamental heat transfer mechanisms involved. This paper presents an overview of studies on thermal issues that affect the material quality of multilayer thin film structures during processing with an infrared heat source

We study size quantization effects on the conduction band dispersion in GaAs/AlAs quantum wells using a semiempirical tight-binding method. For GaAs well thicknesses between 3 and 11 nm, we find a significant increase of the conduction band mass of up to 50% compared with bulk GaAs. Concomitantly, the confinement reduces the highest achievable group velocities for electrons in the Γ conduction valley of the well by up to 30%. We discuss some of the consequences for quantum-well-based devices.

The distribution coefficients for phenol between soil and both sub- and supercritical carbon dioxide were measured by static experiments in the temperature range 297–349 K and the pressure range 9–30 MPa. The effects of soil organic content, soil moisture, temperature, and pressure on the distribution co efficients were investigated. Simple thermodynamic models were developed for temperature and pressure dependency of the distribution coefficients which successfully represent the data. In addition, methanol was tested as an entrainer and experiments were conducted with benzene to investigate the effects of co-pollutants. The results show that the presence of chemicals in the system other than phenol affect the distribution coefficients.

Data and arguments are presented identifying the old phenomenon (1960) of the ‘‘zero‐bias anomaly’’ in III‐V semiconductor p‐n tunneling as a manifestation of the Coulomb blockade. Tunneling involving a Au‐Ge complex in GaAs, which acts as a photosensitive ‘‘quantum dot’’ controlling the p‐n tunneling, provides the basis for a light‐sensitive Coulomb blockade and serves also as a model, an explanation, for the zero‐bias anomaly (V=0) observed in III‐V p‐n tunneling.

Electrons and holes contribute to the charge transport in semiconductors, while ordinary charge transport in metals is restricted to electrons only. Another distinctive feature of semiconductor transport is its inherent nonlinearity in high electric fields. The basic phenomena of high field transport are nonlinear conductance; changed responses to magnetic fields; changed high-frequency response, including the dielectric function; and changed confinement in potential wells or at heterojunctions between different semiconductors. Keywords: nonlinearity; high electric fields; semiconductors; Botlzmann equations; hot electrons

A time‐dependent ensemble Monte Carlo simulation has been developed which includes the computation of the self‐consistent electric field and electron concentration. The Monte Carlo code is used to study transient and steady‐state transport in planar‐doped‐barrier (PDB) GaAs diodes and transistors. Results are presented for the temporal and spatial evolution of electronic transport through the PDB. We show that (i) average velocities achievable with a PDB are significantly above the steady‐state velocities by about a factor of 3, (ii) the rise time of the electric current in the PDB is in the subpicosecond range for diode length below 2000 A, (iii) a pronounced displacement current dominates the transient electronics at onset of injection, and (iv) polar optical phonon absorption contributes significantly to the thermionic‐emission current over the barriers.

The interface trapping noise of surface channel charge coupled devices (SCCd's) is calculated numerically taking fully into account the non-stationary character of the charge transfer. The formula previously given for trapping noise takes into account only the emission of carriers from the traps. It is shown that the capture of carriers can also cause noise when the fat zeros are very small or the clock frequency is high. Detailed formulas for and evaluation of the capture and emission noise are presented, including the energy dependence of the interface state density. Das Grenzflachen-Anhaftrauschen von oberflachenkanalladungsgekoppelten Bauelementen (SCCD) wird numerisch unter vollstandiger Berucksichtigung des nichtstationaren Charakters des Ladungstransfers berechnet. Die fruher angegebenen Formeln fur Anhaftrauschen berucksichtigen nur die Emission von Tragern aus den Haftstellen. Es wird gezeigt, das der Einfang der Trager ebenfalls Rauschen hervorrufen kann, wenn die „fat zeros” sehr klein oder die Taktfrequenz sehr hoch sind. Ausfuhrliche Formeln und die Berechnung des Einfangs- und Emissionsrauschens werden angegeben, einschlieslich der Energieabhangigkeit der Grenzflachenzustandsdichte.

Measurements of the transverse magnetoresistance of n-channel MOS transistors having different amounts of oxide charges are presented. The data show that the details of the wave function perpendicular to the surface must be considered for giving a quantitative interpretation. Qualitatively the electron gas behaves as if it were two-dimensional since the longitudinal magnetoresistance is extremely small. Es werden Messungen der transversalen Magnetowiderstandsanderung von n-Kanal-MOS-Transistoren mit unterschiedlichen Anteilen von Oxidladungen mitgeteilt. Die Werte zeigen, das die Einzelheiten der Wellenfunktion senkrecht zur Oberflache berucksichtigt werden mussen, um eine quantitative Deutung zu erhalten. Qualitativ verhalt sich das Elektronengas als ware es zweidimensional, da die longitudinale Magnetowiderstandsanderung extrem gering ist.

Absorption data on strained GaAs1−xPx-GaAs superlattices (SL, 128-period, barrier size LB≈75 A, quantum-well size Lz≈75 A, alloy composition x≈0.25) are presented in the range 0–10 kbars. The absorption curves obtained show no exciton show no exciton peaks such as seen in lattice- matched AlxGa1−xAs-GaAs SL's, and the pressure coefficient decreases from 11.5 meV/kbar to ≈ 10.5 meV/kbar in the wells and ≈6.5 meV/kbar at energies approaching and above the barrier energies. This behavior is attributed to the fluctuations in strain caused by the alloy disorder, and clustering, of the barriers.

The magnetoresistance of n-silicon inversion layers is measurd in dependence on the drain voltage at fixed temperatures and vs. tempeature at low drain voltages. A one-to-one correspondence of the electric drain fields and temperatures can be deduced from these measurements. The experimental data are taken at temperatures below 30 K. Assuming that the electrons lose energy to acoustic phonos only, the experimental results are compared with a “two-dimensional hot-electron” theory. The coupling constant ZA to the acoustic phonons via the deformation potential is found to be ZA = 5.9 eV, which compares favourably with earlier results. Es wird der Magnetowiderstand von n-leitenden Silizium-Inversionsschichten in Abhangigkeit von der Saugspannung bei festen Temperaturen und als Funktion der Temperatur bei niedrigen Saugspannungen gemessen. Aus diesen Messungen kann auf eine vollige Korrespondenz der elektrischen Saugfelder und Temperaturen geschlossen werden. Die exprimentellen Werte wurden bei Temperaturen unterhalb 30 K bestimt. Unter der Annahme das die Elektronen Energie nur an akustische Phononen verlieren, werden die experimentellen Ergebnisse mit einer Theorie „zweidimensionaler heiser Elektronen” verglichen. Es wird gefunden, das die Kopplungskonstante ZA zu den akustischen Phononen uber das Deformationspotential ZA = 5,9 eV betragt, was mit fruheren Ergebnissen gut ubereistimmt.

The dynamics of surface melting and resolidification of self‐ion‐implanted amorphous silicon (∼4000 A layer) during irradiation with a Q‐switched Nd:glass laser (λ = 1.06 μm) has been studied both theoretically and experimentally. The technique of finite‐difference equations is used to solve the nonlinear one‐dimensional heat conduction equations for the solid and liquid phases, taking into account appropriate time‐dependent boundary conditions for finding the position of the melt front as a function of time. In addition we present experimental results for the time‐dependent optical reflectivity of self‐ion‐implanted amorphous silicon to study the transition from amorphous to crystalline phases during annealing with a Nd:glass laser pulse.

The physics of real‐space transfer transistors has been studied by self‐consistent particle Monte Carlo methods. Results of our simulations reproduce all experimentally known features of these devices. In particular, we study and explain the reasons of negative differential resistance, saturation of drain and substrate currents, the negative transconductance [gm=(ΔId,sat/ΔVsub)

Experimental data for the mobility of InSb, doped by nuclear reactions, are presented. This method of doping guarantees a well known number and a random distribution of impurities. The experimental data are shown to agree surprisingly well with the Brooks-Herring formula for ionized impurity scattering. The agreement is discussed in terms of the partial wave method using the Born approximation and Schwinger's variational method to calculate the phase shifts.

A review of electronic transport in semiconductors in the near ballistic regime is presented. Recent experiments and theories are discussed in detail. It is shown that the basic physics of ballistic transport is qualitatively well understood. Quantitatively much work remains to be done, especially with respect to device applications. Some problems related to applications are discussed in context with hot-electron- and high-electron-mobility-transistors. >

A review of carrier mobility measurements in silicon inversion layers is given with special emphasis on high-field phenomena. Measurements reported in the literature have been performed in a range of lattice temperatures 0.03 K ≤ T L ≤ 300 K for electric drain fields 0 E 5 V/cm, which heat the charge carriers up to thousand and more degrees Kelvin. Numerous transport quantities have been measured in this tremendous temperature range. Special consideration is given to: conductivity, mobility, Shubnikov-de Haas effect, the warm electron coefficient β and the saturation drift velocity. Most results available are for n -channel MOS devices on (100), (110) and (111) silicon surfaces. Only few results are publised for the p -channel. The results are compared with experimental findings for bulk material. The comparison shows that no drastic differences appear at temperatures above 10 K and high electric fields. Only the saturation velocity of inversion layers is lower and the temperature and field dependence of the conductivity is weaker as compared to the bulk. At temperatures below 10 K, however, activated conductivities, giant β-coefficients and in the high field region a voltage controlled negative differential resistance are observed.

A computer simulation of double-drift silicon IMPATT diodes is presented. The model is essentially the conventional drift-diffusion model with two significant improvements; the ionization coefficients are assumed to be functions of carrier temperature rather than local electric field, and a description of the effects of the carriers' thermal conductivity is included [1]. Our model includes all known hot electron effects except velocity overshoot (hot electron drift, diffusion, relaxation, and heat conduction), and is exact within the framework of an electron temperature model.

The conductivity by holes in p -type silicon and the warm carrier energy relaxation time are measured as a function of applied uniaxial stress at 90°K. The results are explained in terms of acoustic phonon scattering. The theoretical expressions allow one to determine the deformation potential constant b from measurements at stresses up to 3×10 9 dyn/cm 2 . Furthermore, a negative differential resistivity at low temperatures and high stresses is obtained from theory.

A theory of the free carrier absorption in acoustoelectric domains is developed by using a generalized current equation and the Poisson equation. The theory is compared with microwave absorption measurements. Using the relative values of the frequency distribution of the acoustic flux in the domains obtained by Brillouin scattering, the absolute values of the AC acoustic potential have been determined from these experiments. The obtained values of the acoustic potential show that gain saturation is not caused by carrier bunching but by parametric conversion processes.

Measurements of the warm hole energy relaxation time of Te in the temperature range between 150°K and 190°K are reported. Experimental data were obtained using a microwave harmonic mixing method. These energy relaxation times are compared with calculated values assuming polar optical scattering as being the dominant energy loss mechanism in this temperature range. Furthermore, deviations from Ohm's law applying weak and medium d.c. fields to Te samples have been investigated and will be discussed.

The energy relaxation time τϵ of GaSb has been determined independently from microwave harmonic mixing experiments in the range of 160–200 K and from the current-voltage characteristics at 300 and 77 K. From measurements of the i.r. Faraday effect at 300 K valley populations as a function of the electric field strength are obtained which are in agreement with values calculated with help of the energy relaxation time obtained by methods mentioned before. For the evaluation of the data a two-band model has been used. The results obtained from the microwave experiments are extrapolated to 300 and 77 K assuming polar optical mode scattering. Good agreement of these values and the results obtained from the current-voltage characteristics and the Faraday measurements was found. The values for 300 and 77 K are 4 × 10−12 sec and approximately 1·6 × 10−11 sec, respectively.

A nonlinear theory is developed for the amplification of ultrasonic waves in thin piezoelectric semiconductor platelets with parallel flat faces. The theory is based on the assumption of a “quasi-standing” monochromatic wave for the acousto-electric potential. The downshift of the amplified frequencies for high acoustic flux, the saturation in the gain of amplification, the form of the current pulse, and the narrowing of the region where round-trip occurs are investigated in detail. The theory is valid for a one-dimensional model and applies to semiconductors where the mean free path of the carriers is small compared to the acoustic wavelength. In a study of the acousto-electric current, it is shown that no current saturation can occur, if the thickness of the platelet is only a few times the acoustic wavelength. This is verified experimentally, and a new type of current oscillations is reported. Es wird eine nichtlineare Theorie der Verstarkung von Ultraschallwellen in dunnen, piezoelektrischen Halbleiterplattchen mit parallelen, flachen Flachen entwickelt. Diese Theorie basiert auf der Annahme einer „quasi-stehenden”, monochromatischen Welle fur das akusto-elektrische Potential. Die Verschiebung der verstarkten Wellen zu niedrigen Frequenzen fur hohen akustischen Flus, die Sattigung des Verstarkungsfaktors, die Form der Stromimpulse und die Verkleinerung des Bereiches, in dem „Round-Trip” auftritt, werden im Detail untersucht. Die Theorie ist fur ein eindimensionales Modell gultig und fur Halbleiter anwendbar, bei denen die mittlere freie Weglange klein im Vergleich zur akustischen Wellenlange ist. Durch eine Untersuchung des akusto-elektrischen Stromes wird gezeigt, das keine Stromsattigung auftreten kann, wenn die Dicke der Plattchen nur einige akustische Wellenlangen betragt. Dies wird experimentell verifiziert und es wird ein neuer Typ von Stromschwingungen beschrieben.

Measurements of non-ohmic microwave conductivity of semiconductors are reported, whereby non-ohmic behaviour is the consequence of a large microwave amplitude. The semi-conductor is arranged in a rectangular waveguide as a circular ‘inductive post’. Incident, transmitted and reflected microwave powers are measured. From there the microwave conductivity is deduced according to a method which was quoted by M arcuvitz (5) and which is specialized on a small post diameter. This method proves itself useful in the microwave X-band for a specific resistivity of more than 1 Ω-cm and is checked against n -type silicon and n -type germanium.

The development of the r-f emission in photoconducting CdS acousto-electric oscillators was studied as a function of time and applied voltage. Several characteristic steps in the current pulse were observed and could be related to special series of oscillating modes. By studying the mode development with time it could be shown that nonlinear processes like parametric down conversion take place. The bandwidth of the frequency modes was found to be a function of the propagation time of the mode. Die Entwicklung einer r-f Emission im photoleitenden CdS-Oszillator wurde als Funktion der Zeit und der angelegten Spannung untersucht. Verschiedene charakteristische Stufen im Strompuls wurden beobachtet und konnten speziellen Serien von Frequenzmoden zugeordnet werden. Durch Untersuchungen der Modenentwicklung mit fortschreitender Zeit konnte gezeigt werden, das nichtlineare Prozesse wie z. B. eine parametrische Abkonversion auftreten. Es wurde weiter gefunden, das die Halbwertsbreite der Frequenzmode eine Funktion der Laufzeit der Mode ist.

The spatial fluctuation in barrier heights of a planar‐doped barrier due to the discreteness of the acceptors and their statistical distribution has been calculated by solving Poisson’s equation in three dimensions. Our model assumes a random distribution of spherical acceptor charges. Nonlinear Thomas–Fermi screening has been used to include the effect of free carriers and to determine their position‐dependent concentration. At 4.2 K we find a range in barrier heights of 30 meV for a barrier with an average value of 0.206 eV. The method by which potential fluctuations broaden the energy distribution of ballistic electrons is illustrated by an example.

Experimental observation of resonant tunneling in a strained-layer double-barrier, single-well GaAs1−xPx-GaAs (x ≈ 0.3) quantum-well heterostructure (QWH) is reported. Tunneling via quasi-two-dimensional states in the center GaAs quantum well is confirmed by anisotropy of the d2IdV2 characteristic in a strong perpendicular magnetic field (B∥) as compared to a parallel field (BB⊃. Transmission electron microscopy is used to show the effect of dislocations in introducing asymmetry in the tunneling I-V characteristics.

The scattering rates for the electron‐impurity and the electron‐phonon interactions in semiconductor multilayer heterojunction structures are calculated. It is found that phonon scattering is enhanced in such structures, whereas, impurity scattering can be strongly reduced at low temperatures as found experimentally.

The Boltzmann Equation is solved for a two dimensional gas of charge carriers in order to calculate the conductivity of field-effect transistors. The charge carriers are assumed to be scattered by point charges. The scattering process is treated in Born approximation. The resulting conductivity tensor is in apparent disagreement with experimental results.

We present a theory of deformation potential electron–phonon scattering in the bulk, in superlattices, and at interfaces of semiconductors. Expressions for the acoustical deformation potential constants are obtained in closed form for bulk semiconductors and for a monolayer superlattice. Deformation potential constants are evaluated numerically for superlattices of various thicknesses. The results are in good agreement with available experiments and provide a detailed understanding of deformation potential scattering.

A new scattering mechanism for free carriers in inversion layers is proposed. It is shown that polar optical phonons of the insulator couple effectively to the inversion layer electrons in the adjacent semiconductor. For the Si-SiO2 interface this scattering by remote polar phonons influences substantially the field dependent mobility of the silicon inversion layer carriers.

A new explanation of carrier heating within silicon inversion layers is offered which is in full accordance with classical laws. We show that, as is usually assumed, the heating is due to the longitudinal electric field. However, also the transverse field influences the electron temperature by determining the minimum kinetic energy and therefore influencing the electron mobility. In this way the distribution function is heated above that in bulk material as witnessed by the significant increase in measured noise figures and in the calculated electron impact ionization rate.

The current-voltage characteristics of MOS field-effect transistors is investigated theoretically and experimentally in the region of extremely high drain electric fields E D using the electron temperature concept in the classical three-dimensional theory. It is found that the drain field at which the drain current becomes non-ohmic on the basis of hot electron effects is related to the surface field E zs by E D ∼√ E zs . Other expressions for the field dependent mobility are also given which allow the construction of the current-voltage characteristics.

We investigate the scattering of electrons in a quasi‐two‐dimensional electron gas by acoustic phonons at low temperatures. In contrast to scattering at high temperatures, we find that at low temperatures the average scattering rate is dominated by phonon modes with energies much larger than kT. An analytic calculation of either the energy‐loss rate or the mobility depends on approximations which are valid only for small phonon wave numbers. Because of the contribution of high‐energy phonons, these approximations remain inappropriate to much lower temperatures than previously supposed. For most cases, we find that the approximate analytic solution differs significantly from a more accurate solution obtained by numerical integration.

Measurements of the infrared absorption by acoustoelectric domains in ZnO at a wavelength of 10.6 mu m are reported. The results give good agreement with a theory recently published by the authors.

Experimental results for the energy loss of charge carriers to acoustic phonons in quasi-two-dimensional systems are discussed in terms of current theories.

Measurements are reported of the current-voltage characteristic of n-CdS which agree with values calculated by Nag (1972).

Liquid phase epitaxy by conventional tipping technique has been employed for the growth of high purity epitaxial layers. The layers were grown at 720°‐560°C on (100) and (111) oriented InP substrates. Characteristic surface structures for the substrate orientations as a function of the growth temperature were observed. The layers were characterized by Hall data and photoluminescence measurements at low temperatures. The simultaneous observation of the band‐acceptor and donor‐acceptor pair transition due to the main acceptor in our LPE‐layers is reported. The binding energy of this acceptor is determined to .