A new method for investigating conduction phenomena in semi-conductors

Abstract

Langmuir has shown that in low pressure gas discharges, that part of the discharge usually referred to as the positive column consists of equal numbers of positive ions and electrons per unit volume, and to this portion he has given the name “plasma”. He has shown, moreover, that the current passing between cathode and anode is proportional only to the difference between the number of electrons passing in the direction of cathode to anode across 1 sq cm placed normally to the tube axis and the number of electrons passing across the same area in the opposite direction. The random electron current density is usually many times the anode current density. The electrons in the plasma have been shown by Langmuir to have a Maxwellian distribution of velocities and that they can therefore have ascribed to them a mean energy, V e , corresponding to a temperature T where, as in the kinetic theory of gases V e = 3/2 k T (1) or T = 2/3 × 1.59 × 10 -20 /1.37 × 10 -16 × 10 8 Kelvin degrees per volt = 7730°K per volt. In low pressure gas discharges T varies from 5000°K to 30,000°K or the mean energy of electrons expressed in electron volts varies from about 0.5 to 4 volts.