Search

Describes the ecology of Chondrilla juncea in the western Mediterranean. Relation to human disturbance, soil characteristics and other plant species; Relation to the organisms, Puccinia chondrillina, Erysiphe cichoracearum; Relation to various snail species, Leveilula taurica and Aceria chondrillae which damage or destroy the plant.

Indiffusion of impurities into a semiconductor takes place at high temperatures. In the case of heterojunction transistors, the impurity concentration on the emitter side of the base approaches or even exceeds the intrinsic concentration of electrons and holes at the temperature of impurity indiffusion. As a result, the profile of impurity concentration in the base is not the complementary error function for an infinite source. This is due to field-aided diffusion by ionized impurities resulting in a variable diffusion coefficient for such impurities.
The resulting non-linear differential equation has been solved on a digital computer, to obtain the exact profile of impurity concentration in base. Using this profile, base transit time and overall cut-off frequency have been computed for a particular transistor of Jadus (1967).
In this paper the resulting non-linear differential equation of diffusion has been solved by numerical techniques on a digital computer. The profiles of impurity distribution for fixed and variable diffusion coefficients have been plotted for a typical case, to show the difference between the approximate and exact solutions. The base transit time has been evaluated, based on the correct impurity profile. The variation of impurities results in a minority carrier diffusion coefficient, D, ranging between 122 and 3 cm/sec. These variations are much greater than those encountered by Pritchard (1962), so that his approximations are invalid for this situation. [ABSTRACT FROM AUTHOR]