Incomplete Ionization Research Articles

Double diffused gallium arsenide transistors

Double diffused gallium arsenide transistors utilising a basewidth of 0·3 μ to overcome low minority carrier lifetime have been made. The npn mesa structures use zinc as a base-dopant and tin for the emitter. The impurity concentration of the starting material is limited to about 1 × 10 16 cm −3 because of the tendency to thermal conversion. The highest emitter doping achieved is about 2 × 10 19 cm −3. These restrictions require a base diffusant with surface concentrations of the order 10 17 cm −3. Among the available acceptor impurities zinc was chosen over manganese (incomplete ionization at room temperatures), and cadmium (surface reactions). A three-step diffusion cycle was developed in order to reduce the zinc surface concentration several orders of magnitude from ordinary vapor phase diffusions to the desired level. To achieve complex emitter patterns, methods parallel to those used for silicon were developed. Resulting devices have operated at junction temperatures from liquid nitrogen to 350°C. The d.c. current gain is typically 6 at a collector current of 80 mA, with values as high as 15 observed. The variation of current gain with temperature is typically ±15 per cent from −196°C to +350°C. An a.c. power output of 1 W was measured at 50 Mc with 60 per cent conversion efficiency ( I C = 80 mA, V CE = 20 V). The units show a current gain-bandwidth frequency f t = 300 Mc with the best transistors having a f t as high as 600 Mc.

Double diffused gallium arsenide transistors

Abstract Double diffused gallium arsenide transistors utilising a basewidth of 0·3 μ to overcome low minority carrier lifetime have been made. The npn mesa structures use zinc as a base-dopant and tin for the emitter. The impurity concentration of the starting material is limited to about 1 × 1016 cm−3 because of the tendency to thermal conversion. The highest emitter doping achieved is about 2 × 1019 cm−3. These restrictions require a base diffusant with surface concentrations of the order 1017 cm−3. Among the available acceptor impurities zinc was chosen over manganese (incomplete ionization at room temperatures), and cadmium (surface reactions). A three-step diffusion cycle was developed in order to reduce the zinc surface concentration several orders of magnitude from ordinary vapor phase diffusions to the desired level. To achieve complex emitter patterns, methods parallel to those used for silicon were developed. Resulting devices have operated at junction temperatures from liquid nitrogen to 350°C. The d.c. current gain is typically 6 at a collector current of 80 mA, with values as high as 15 observed. The variation of current gain with temperature is typically ±15 per cent from −196°C to +350°C. An a.c. power output of 1 W was measured at 50 Mc with 60 per cent conversion efficiency (IC = 80 mA, VCE = 20 V). The units show a current gain-bandwidth frequency ft = 300 Mc with the best transistors having a ft as high as 600 Mc.

Messung der radialen Elektronendichte- und Magnetfeldverteilung beim Thetapinch und Vergleich mit numerischen Rechnungen

In a θ-pinch the electron density as function of space and time has been measured bya MACH-ZEHNDER interferometer. Also the magnetic fields have been determined with help of magnetic probes. These experimental results are compared with the hydromagnetic theory. The agreement between these two holds for several compressions in the case of a captured parallel field, however, only for one compression for the antiparallel field. The disagreement for later times for the parallel field case can be explained by end losses and incomplete ionization which is not taken into account in the theory. In the antiparallel field case, however, the disagreement cannot be explained by generalizing the hydromagnetic theory. It seems almost sure that microinstabilities will cause the fast mixing of magnetic fields found experimentally.

Equilibrium properties of a partially ionized plasma

A model for a partially-ionized, partially-dissociated plasma has been formulated using known theoretical concepts to describe both bound and free electron states, internal molecular degrees of freedom and Coulomb interactions. It has been applied to a system of particles arising from the hydrogen molecule. The Coulomb interaction is treated in the classical Debye approximation. However, a distance of closest approach between ions and electrons depending on the kinetic energy of the electrons is included to avoid the short range divergence of the Coulomb potential. The kinetic energy of the free electrons is calculated from the partition function for a perfect Fermi gas. The vibrational and rotational motion is treated in the harmonic oscillator and rigid rotor approximation with the number of energy levels counted for a given electronic state depending on the dissociation energy of the state. A volume dependence of the bound electronic energy eigenvalues is included by considering the effect of surrounding particles as a confinement of a given particle to a spherical box of variable size. For the counting of the bound electronic states, a given state is bound until its energy increases to zero due to confinement. From the partition function for the entire system, the free energy is calculated. By a minimization of the free energy of the system, the equilibrium composition as a function of temperature and volume is obtained. Then not only can thermodynamic quantities be calculated, but it is believed that a reasonable approximation to the correct balance of molecular, ionic and free electonic states is achieved over a wide range of V-T space. Consequently, regions where incomplete ionization and dissociation are important are delineated. In addition, for different regions of V-T space, the relative contributions of charged particle interactions, non-classical behaviour of electrons, internal degrees of freedom and translation to the total energy of the system can be determined.

Equilibrium Properties of a Partially Ionized Plasma

A model for a partially ionized, partially dissociated plasma has been formulated using known theoretical concepts to describe both bound and free electron states, internal molecular degrees of freedom and Coulomb interactions. It has been applied to a system of particles arising from the hydrogen molecule. The Coulomb interaction is treated in the classical Debye approximation. However, a distance of closest approach between ions and electrons depending on the kinetic energy of the electrons is included to avoid the short-range divergence of the Coulomb potential. The kinetic energy of the free electrons is calculated from the partition function for a perfect Fermi gas. The vibrational and rotational motion are treated in the harmonic oscillator and rigid rotor approximation with the number of energy levels counted for a given electronic state depending on the dissociation energy of the state. A volume dependence of the bound electronic energy eigenvalues is included by considering the effect of surrounding particles as a confinement of a given particle to a spherical box of variable size. For the counting of the bound electronic states, a given state is bound until its energy increases to zero due to confinement. From the partition function for the entire system, the free energy is calculated. By a minimization of the free energy of the system, the equilibrium composition as a function of temperature and volume is obtained. Then not only can thermodynamic quantities be calculated, but it is believed that a reasonable approximation to the correct balance of molecular, ionic and free electronic states is achieved over a wide range of $v\ensuremath{-}T$ space. Consequently, regions where incomplete ionization and dissociation are important are delineated. In addition, for different regions of $v\ensuremath{-}T$ space, the relative contributions of charged particle interaction of the nonclassical behavior of electrons, of internal degrees of freedom and of translation to the total energy of the system can be determined.

Magnetic Susceptibilities of Sulfur, Selenium and Tellurium from Room Temperature to 1100°C

Abstract (1) The susceptibility of sulfur showed the first change at about 157°C, showing no changes at the melting point and its neighborhood.The change is attributed to the radical chains owing to the scission of eight-membered sulfur rings. (2) On fusion the susceptibility-temperature curve for glassy selenium deflected toward sides opposite to that for hexagonal selenium. It is considered that the decrease in susceptibility of glassy selenium can be ascribed to free radicals produced by the scission of selenium rings. On cooling, liquid selenium turned to glassy selenium, showing the increase in susceptibility at about 125°C. It can be considered that this change is related to the reclosing of chains into rings. (3) The susceptibility of hexagonal tellurium decreased abruptly on fusion. It may be considered that this change is due to a paramagnetic contribution from unpaired spins produced by incomplete ionization of the valence shell. (4) The susceptibility-temperature curves for sulfur and selenium were deflected toward paramagnetic sides above 353° and 690°C, respectively. The paramagnetism increased reversibly with temperature, while the susceptibility of tellurium was independent of temperature to 1100°C. On sulfur and selenium, the ratios of the weight of the diatomic molecule to the total weight at every temperature were obtained from the weight of the diatomic molecule estimated by comparing the experimental value of paramagnetic susceptibility with the value calculated from Van Vleck’s equation.

Handbuch der Experimentalphysik

THE last decade witnessed a violent revolution in our fundamental conceptions of the electrochemistry of solutions, in the course of which the classical theory of Arrhenius, postulating incomplete ionisation of strong electrolytes and constant ionic mobilities, was dethroned in favour of the Debye-Huckel theory, postulating complete ionisation with ionic mobility a function of concentration. In a sense, this revolution is still incomplete, since several important points in the Debye-Huckel theory are not yet satisfactorily developed and the original ideas of Arrhenius must still be called into service hi connexion with weak and transition electrolytes, but remarkable changes have been effected in a domain where conditions were long regarded as settled and, after a great deal of natural hesitation in certain quarters, practically all the experts in the field have now reconciled themselves to the new regime. Handbuch der Experimentalphysik. Herausgegeben von W. Wien F. Harms. Unter Mitarbeit von H. Lenz. Band 12: Elektrochemie. Herausgegeben von K. Fajans. Teil 1: Leitfahigkeit und Uberfuhrungszahlen in flussigen und festen Elelctrolyten. Von Prof. Dr. L. Ebert und Prof. Dr. C. Tubandt. Pp. xvi + 496. (Leipzig: Akademische Verlagsgesellschaft m.b.H., 1932.) 45 gold marks.