Low Temperature Hall Mobility and Magnetoresistance in KCl at High Electric Field

Abstract

Hall mobility of photoelectrons in zone refined and additively colored KCl single crystals is found to be so high as 2×10 4 cm 2 /volt·sec at 4.2°K and to decrease in proportion to E -0.5 beyond a critical electric field. Corresponding to the mobility decrease, photocurrent is proportional to E 0.5 beyond the critical field. Dominant scattering centers at low electric field are concluded to be charged impurities rather than F centers by measurements of Hall effect and magnetoresistance. Polaron transport in KCl crystal is interpreted fairly well by the usual transport theory including hot electron theory. However, two important difficulties become noticeable in applying the usual theory. First, the trapping lifetime of electron is shorter than the scattering time. Secondly, photocurrent saturation is not observed even under very high electric field at which drift velocity of electron is much higher than the thermal velocity and emission of optical phonon is expected to occur appreciably.