Simple Semiconductor Research Articles

Theory of spin-polarized electron-hole liquid

The properties of an electron-hole liquid with different densities of spin-up and spin-down carriers have been calculated for a simple semiconductor model and CdS. The spin polarization lowers both equilibrium density and binding energy. Exchange leads to a different energy gap for each spin direction which can be detected in the circular polarization of the luminescence.

Relation Between an Atomic Electronegativity Scale and the Work Function

Recently compiled data for the first electron affinity and the first ionization potential are used to obtain values for an atomic electronegativity scale, based on the Mulliken relation. From this scale and a new compilation of work function data, a linear equation is obtained which includes a parameter for any given element, depending on its subgroup in the periodic table. Data are plotted for 51 elements, including simple metals, transition metals, and semiconductors. These data fit the straight-line equation better than 10 percent. Data for the transition metals deviate within the same limits as those for elements having simpler electronic configurations. The electronegativity scale differs significantly from the Pauling scale and is shown to be a useful guide to preferred values of the work function for elements.

Scratch filter using c.c.d.s

This letter describes the use of charge-coupled devices in the automatic real-time editing of audio signals. A simple semiconductor device is used to replace a number of complex digital circuits.

Semiconductor Si(npn) detector with two surface-barrier junction

A simple semiconductor detector having surface-barrier junctions on both sides of the p-type silicon wafer is described.

Recombination-induced non-equilibrium phase transitions in semiconductors

Electron-hole and excitonic recombination processes in simple semiconductors are analysed for possible non-equilibrium phase transitions. A second-order type transition is found to be possible when impact ionization under an external electric field and radiative and Auger recombinations are taken into consideration. The order parameter of the transition is the electron concentration, and the control parameter is Ci-l where Ci is the impact ionization coefficient and l is an inverse carrier life-time for processes not considered explicitly. Using the Shockley model, some simple numerical estimates of the concentrations and electric field involved are made. It has also been shown that the quantum character of the carriers in semiconductors greatly limits the possibility of first-order-type phase transitions when one or two distinct types of fermions are involved with boson excitation.

Modification of phonon distribution in degenerate semiconductors by high electric fields: Effect on transport coefficients

AbstractDrift mobility, Hall mobility, and Hall coefficient of a degenerate semiconductor at very low temperatures and high electric fields are calculated. Following Paranjape's approach the modified distribution of phonons are taken into account in the calculation of the transport coefficients for arbitrary degeneracy of simple model semiconductors. The electron scattering due to ionized impurities as well as due to acoustic phonons have been considered. The calculations show that the inclusion of the modified phonon distribution in the theory reduces the theoretical values of drift and Hall mobilities of degenerate semiconductors by a factor of two or more; its effect on Hall coefficients is to decrease the theoretical value slightly (20%).

Nonlocal dielectric susceptibility of a semi-infinite insulator

The excitonic contribution to the dielectric susceptibility of a semi-infinite simple cubic semiconductor bounded by a (001) surface is calculated in the tight-binding approximation. The electron and hole hopping integrals in the Hamiltonian for the system couple only nearest-neighbor sites, and the Coulomb interaction between the electron and hole occurs at a single site. A pair of free surfaces is created in an infinitely extended crystal by setting to zero the electron and hole hopping integrals connecting sites on opposite sides of a fictitious plane normal to the [001] direction, but containing no atoms itself. The integral equation for the two-particle Green's function in terms of which the susceptibility is expressed is solved analytically for frequencies in the excitonic regime. The dispersion relation for surface excitons is obtained, and the spatial variation of the polarization in the crystal induced by a spatially uniform macroscopic field is determined from our results.

The hall effect and the thermopower of two simple heavily doped semiconductor models

AbstractThe single‐site approximation is used in order to study the effect of randomly distributed point scatterers on the most important transport properties of two simple semiconductor models. The one consists of two parabolic and the other of two simple‐cubic tight‐binding bands. Numerical results are given for energy‐dependent (density of states, conductivity, Hall conductivity) and temperature‐dependent quantities (conductivity, Hall mobility, thermopower).

Fibre delay equalization by carrier drift in the detector

The transmission of optical multimode carriers via clad glass fibres has many advantages, but in general introduces severe signal distortion because of mode delay differences. We describe a simple semiconductor receiver capable of equalizing these delay differences at the fibre end. A tenfold increase in bandwidth (data rate) should be possible by this means if mode coupling in the fibre is not excessive.

Crystalline and disordered solids

There are several areas where results have reached an interesting stage. With the simple semiconductors we are learning about their behaviour under such extreme conditions as high pressures, high temperatures, large electric and magnetic fields and high light intensities.

The field-effect modified transistor: a high-responsivity photosensor

A new photosensing device that can be described as a field-effect modified bipolar transistor, has been developed. A novel technique of reducing the effective collector capacitance without reducing the total primary photocurrent provides for a decade improvement in responsivity for the FEM phototransistor operating in the charge-storage mode. Other applications of this device include a high noise-immunity inverter, a light intensity-to-frequency converter, and a simple semiconductor memory element. FEM transistors can be fabricated using the same processing schedule used for conventional bipolar transistors; no additional steps are required.

Simple semiconductor correlator for picosecond light pulses

A semiconductor correlator was developed for measuring the second-order moment and the correlation function of ultrashort light pulses. A simple device was built utilizing a two-photon-absorbing crystal of CdS0.6CdSe0.4.

Zur Interpretation der Röntgenemissionsbanden von AIII BV‐Verbindungen

AbstractThe experimental data on the x‐ray emission bands of AIII BV compounds corresponding to transitions with valence band states as initial states are compiled. The comparison of the observed emission band widths and line shapes with band structure data and also with the simple semiconductor model due to PENN shows that most of the observed structure can be explained if one assumes that the K‐emission bands reflect the p‐like part and the L‐emission bands the s‐(and d‐) like parts of the total valence band state density.

On the theory of the electric conductivity of solids in a strong electric field

AbstractA theory of the electric conductivity is given for a simple semiconductor model in the presence of a strong electric field including both the heating of the charge carriers and the field‐induced change of the density of states. The conductivity is divided into an interband and an interband part. The intraband part defines the field‐dependent plasma frequency. The interband conductivity vanishes in absence of the strong field and shows an exponential growth as the field is increased. The connection of this result with the Zener tunneling of electrons between the valence and the conduction bands is discussed.

An Undergraduate Materials Laboratory for Electrical Engineers

The understanding of solid-state electronic materials is greatly improved by a laboratory, particularly at the undergraduate level where a complete theoretical treatment of the subject is not possible. In the laboratory described in this paper, students work on term projects dealing with the measurement of fundamental electrical and optical characteristics of semiconductors and with the fabrication of simple semiconductor devices. The students are given a great deal of freedom in choosing and developing their own techniques and instrumentation.

A pseudopotential classification of crystal structure for some simple AB semiconductors

Using pseudopotential form factors we can separate a number of compounds into ionic or covalent bonding type. The form factors depend only on the ionic charge and a scaled empty core radius of the constituent atoms.

Calculations of Some Transport Coefficients in Simple Semiconductors at Low Temperatures and High Electric Fields

In this paper the authors have calculated Hall mobility, drift mobility, and Hall constant for a non-degenerate simple model semiconductor at low temperatures for an arbitrary electric field strength. Following Paranjape the modified distribution of phonons has been taken into account. The difference between the calculations of transport coefficients made by taking into account the modified phonon distribution and by not taking it into account is quite appreciable at high electric field. Calculations also show that for Ne = 1016/cm3 the mobility of electrons remains temperature dependent.

The effect of pressure on the electronic structure and atomic form factors of group IV semiconductors: A self consistent pseudopotential approach

We construct a set of linear equations which allow for an aproximately self consistent evaluation of the pseudopotential form factors and band structure under pressure in simple semiconductors. Good results are obtained for Ge and Si.

Electrical Properties of Semiconducting CdF2:Y

Measurements of resistivity and the Hall coefficient in the temperature range 425-4.2\ifmmode^\circ\else\textdegree\fi{}K have been made on single crystals of semiconducting Cd${\mathrm{F}}_{2}$ doped with yttrium (Y). The Y concentrations ranged from 0.002-1 mole%. The characteristic behavior of impurity-band conduction is observed, with the activation energies ${\ensuremath{\epsilon}}_{1}$, ${\ensuremath{\epsilon}}_{2}$, and ${\ensuremath{\epsilon}}_{3}$. The onset of impurity-band conduction occurs at higher temperatures than in other semiconductors. No degeneracy effects are seen for the highest concentrations observed. The data are analyzed on the basis of simple semiconductor theory, assuming a hydrogenic nature of the Y donor. Using the value of effective polaron mass ${m}_{p}\ensuremath{\approx}0.9{m}_{e}$ and the static dielectric constant ${\ensuremath{\epsilon}}_{0}=8.1$, we find that the calculated ionization energy is larger than the experimental value. The impurity-banding behavior cannot be characterized in a fashion similar to what has been done in other semiconductors. Alternative analyses are suggested. The Hall coefficient is analyzed on the basis of the two-band model: the conduction band and the impurity band. At temperatures above 250\ifmmode^\circ\else\textdegree\fi{}K, the Hall-mobility data can be fitted by assuming polar optical mode and an acoustic mode as the dominant scattering mechanisms. The deformation potential was found to be 8.2\ifmmode\pm\else\textpm\fi{}1 eV. Below 250\ifmmode^\circ\else\textdegree\fi{}K, ionized impurity-scattering is the additional mechanism. At temperatures below \ensuremath{\sim}80\ifmmode^\circ\else\textdegree\fi{}K, the mobility falls off sharply owing to impurity banding.

Rapidly convergent pseudopotentials for crystalline systems

A new formulation of the pseudopotential theory has been developed for crystalline systems. A Green function version of the plane-wave secular equation is the starting point for the reformulation, and the Ewald technique and a Ziman transformation are used to obtain a plane-wave representation in which the pseudo-potential matrix elements decay very rapidly as the wave vector increases. This reformulation explains the observation of Falicov and Golin that the conventional pseudopotential secular equation converges only very slowly and can give markedly worse agreement with the experimental data than a parameterized secular equation with rapidly decaying matrix elements. An explanation is offered for the fact that the empirical pseudopotential method is successful even for materials for which no pseudopotential exists. The reformulated pseudopotential appears to be ideally suited to calculating the physical properties of simple metals and non-polar semi-conductors.