Investigation about the hot-carrier repelling effect in semiconductor devices, using an analytical solution of the hydrodynamic model

Abstract

In this paper, the author discusses the consequences of the back-thermal diffusion of hot carriers, using an analytical solution of the hydrodynamic model (HDM). He observed a total deformation in the carrier distribution, around the reverse-biased semiconductor junctions, due to the back-thermal diffusion mechanism. At sufficient reverse bias, the diffusion of minority carriers (generation in neutral regions) is found to be influenced by the carrier-temperature gradient. Therefore, charge carriers are pushed forth (by electric-field effect) and back (by the thermal gradients) and the balance between these forces are controlled by the applied bias value. This may explain the origin of the terahertz oscillations in semiconductors after excitation by ultrafast laser pulses, which is currently an issue of debate. In order to confirm the validity of the proposed theory, the transport of hot carriers across a reverse-biased p-i-n diode is simulated using the HDM, and the conventional drift-diffusion model. He shows that the number of hot minority carriers is not null at the junction boundary, but has an appreciable value, as if they are repelled back from the junction boundary to the cold neutral-region side, by thermal diffusion. He also proposes a simple analytical solution of the set of hydrodynamic equations, to demonstrate his theory of hot-carrier transport in semiconductor devices in general and across p-n junctions in particular. On the basis of his analysis, he discusses the terahertz generation from a reverse-biased p-i-n diode, which is subjected to femtosecond laser pulses