This paper reports an experimental and theoretical analysis of the diffusivity of electrons in Si as function of temperature, field strength, and field direction. Results for the longitudinal diffusion coefficient have been obtained experimentally for fields applied along (111) and (100) directions with time-of-flight and noise measurements. Calculations have been performed with the Monte Carlo procedure. The theoretical analysis, which includes an extensive discussion of the intervalley diffusion process, has yielded a revised version of the silicon model which correctly interprets both the new diffusion data and other well-established electron transport properties. The revision of th~ model is mainly concerned with the relative weights of/ and g intervalley scattering mechanisms. In fact the interpretation of the anisotropy of the diffusion allows separate estimates of the two types of scattering through their different effects on the intervalley diffusion which comes about when electrons have different drift velocities in different valleys.

A critical discussion is given of existing methods for the computation of noise in single injection space−charge−limited (SCL) devices: the salami method, the Langevin method, and the impedance field method. In addition, a new method is set forth, which in one form (finite volume divisions Δ3r) presents a lumped network description of noise and electrical parameters, whereas in another form (Δ3r→0) it presents a continuous media transport picture which is characterized by a transfer impedance tensor. The first form ties in with a modified salami method, whereas the second form is the substratum from which the more global impedance field formulas can be derived. A necessary and sufficient condition under which the noise is expressible as generalized Nyquist noise is obtained. For the simplest device, the thermal electron trap−free insulator, this is applied to one−dimensional as well as some three−dimensional geometries.

The noise of single injection diodes of varying degrees of complexity is studied: the trap−free insulator, the trap−free semiconductor, structures with traps, and three−dimensional insulators. Where possible, results for hot as well as thermal carriers are derived. The one−dimensional results are consistently obtained with the transfer impedance method and the emphasis is on results valid in the entire characteristic [Ohmic, space−charge−limited (SCL), and mixed conduction]. Agreement with other work in limiting current regimes is generally observed. For devices with traps explicit new formulas for the trapping noise are obtained.