Enhancement of Average Velocity of Hot Carriers in Saw-Toothed Heterostructures

Abstract

The response time of many electronic devices is defined mainly by the average electron velocity and by the device dimensions. The ways to reduce the dimensions of electronic devices are well known. We consider some opportunities of the increase of the average velocity of ensemble of electrons in heterostructures (HS). The average velocity of electrons in semiconductors in strong field is saturated due to the scattering with emission of longitudinal optical phonons (LOP). The motion of an electron consists of two stages: acceleration and optical phonon emission. Acceleration of an electron by the electric field gives the increase of energy. Emission of LOP leads to the loss of energy and, hence, to the loss of velocity of electron. Such cyclic motion at low temperatures and strong fields results in the distribution functions of the streaming type [1] and in the occurrence of the inversion [2]. The usage of the peculiarity of these distributions gives an opportunity to increase the average electron velocity at certain conditions. We consider for this purpose the HS with special layers intended for the stimulation of emission of LOP at assigned places. The spatially localized emission of LOP gives an opportunity to change the differential mobility in strong field and enhance the average velocity of hot carriers in the case of vertical transport. It seems that this effect will be useful both for improving of existing devices and for constructing new devices utilizing the effect of enhancement of velocity.